NKCS - Grade 6 - Unit 2
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Transcript of NKCS - Grade 6 - Unit 2
NKCS - Grade 6 - Unit 2 -Ecology
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Contents
1 Interactions of Living Things 11.1 Ecology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21.2 Features of Populations and Growth Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
2 Energy Flow 162.1 Producers, Consumers, and Decomposers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172.2 Energy Flow in an Ecosystem . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232.3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3 Adaptations and Evolution of Populations 303.1 Adaptation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313.2 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
4 Environmental Factors 434.1 Importance of Biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444.2 Human Causes of Extinction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 474.3 Outdoor Air Pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 514.4 Sources of Water Pollution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 554.5 Habitat Destruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594.6 Reduce, Reuse, and Recycle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 654.7 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
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CHAPTER 1 Interactions of LivingThings
Chapter Outline1.1 ECOLOGY
1.2 FEATURES OF POPULATIONS AND GROWTH PATTERNS
1.3 REFERENCES
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1.1 Ecology
I can identify relationships in an ecosystem.
Do organisms live in isolation?
No, organisms are not separated from their environment or from other organisms. They interact in many ways withtheir surroundings. For example, these deer may be drinking from this stream or eating nearby plants. Ecology isthe study of these interactions. Understanding ecology is in part understanding the biology of our planet. And it caneasily be argued that this is especially important today. We literally hold the future of our planet in our hands. Thelessons in this concept discuss ecology, and all the related aspects that make up an ecosystem.
Introduction to Ecology
Life Science can be studied at many different levels. You can study small things like cells. Or you can study bigthings like a group of animals. You can also study the biosphere , the part of the Earth, including the air, land, surfacerocks, and water, where you can find life. This includes the crust, water and atmosphere.The study of the biosphereis part of ecology, the study of how living organisms interact with each other and with their environment.
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Research in Ecology
Ecology involves many different fields, including geology, soil science, geography, meteorology, genetics, chemistry,and physics. You can also divide ecology into the study of different organisms, such as animal ecology, plant ecology,insect ecology, and so on.
Ecologists also study biomes. A biome is a large community of plants and animals that live in the same place. Forexample, ecologists can study the biomes as diverse as the Arctic, the tropics, or the desert. They may want to knowwhy different species live in different biomes. They may want to know what would make a particular biome orecosystem stable. Can you think of other aspects of a biome or ecosystem that ecologists could study?
Ecologists do two types of research:
1. Field studies.2. Laboratory studies.
Field studies involve collecting data outside in the natural world. An ecologist who completes a field study maytravel to a tropical rainforest to study, count, and classify all of the insects that live in a certain area. Laboratorystudies involve working inside, usually in a controlled environment. Sometimes, ecologists collect data from thefield, and then they analyze that data in the lab. Also, they use computer programs to predict what will happen toorganisms that live in a specific area. For example, they may make predictions about what happens to insects in therainforest after a fire.
Organisms and Environments
All organisms have the ability to grow and reproduce. To grow and reproduce, organisms must get materials andenergy from the environment. Plants obtain their energy from the sun through photosynthesis, whereas animalsobtain their energy from other organisms. Either way, these plants and animals, as well as the bacteria and fungi, areconstantly interacting with other species as well as the non-living parts of their ecosystem.
An organism’s environment includes two types of factors:
1. Abiotic factors are the parts of the environment that are not living, such as sunlight, climate, soil, water, andair.
2. Biotic factors are the parts of the environment that are alive, or were alive and then died, such as plants,animals, and their remains. Biotic factors also include bacteria, fungi and protists.
Ecology studies the interactions between biotic factors and abiotic factors. For example, all animals (biotic factors)breathe in oxygen (abiotic factor). All plants (biotic factor) absorb carbon dioxide (abiotic factor) and need water(abiotic factor) to survive.
Can you think of another way that abiotic and biotic factors interact with each other?
Levels of Ecological Organization
How is your school organized?
Your school is organized at several levels. Individual students and teachers are divided into classes. These classesare organized into an entire middle school. Your middle school and other nearby schools are organized into a schooldistrict. Just like schools are organized, ecosystems are also organized into several different levels, and an ecosystemcan be studied at any one of the various levels of organization.
Ecosystems can be studied at small levels or at large levels. The levels of organization are described below from thesmallest to the largest:
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• A species is a group of individuals who are genetically related and can breed to produce fertile young.Individuals are not members of the same species if their members cannot produce offspring that can also havechildren. The second word in the two word name given to every organism is the species name. For example,in Homo sapiens, sapiens is the species name.
• A population is a group of organisms belonging to the same species that live in the same area and interactwith one another.
• A community is all of the populations of different species that live in the same area and interact with oneanother. A community is composed of all of the biotic factors of an area.
• An ecosystem includes the living organisms (all the populations) in an area and the non-living aspects of theenvironment ( Figure below). An ecosystem is made of the biotic and abiotic factors in an area.
FIGURE 1.1Satellite image of Australia’s Great BarrierReef, an example of a marine ecosys-tem.
• Ecologists study ecosystems at every level, from the individual organism to the whole ecosystem. They canask different types of questions at each level. Examples of these questions are given in Table 1.1, using thezebra (Equus zebra) as an example.
TABLE 1.1: Ecological Questions
Ecosystem Level QuestionIndividual How do zebras keep water in their bodies?Population What causes the growth of a zebra populations?Community How does a disturbance, like a fire or predator, affect
the number of mammal species in African grasslands?Ecosystem How does fire affect the amount of food available in
grassland ecosystems?
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Can you illustrate each level in the pyramid above?
Vocabulary
• abiotic factor: Aspect of the environment that is not a living organism, such as soil, water or air.• biotic factor: Components of the environment that are living, or were alive and then died, such as plants or
animals.• ecology: Study of how living organisms interact with each other and with their environment.• species: a group of individuals who are genetically related and can breed to produce fertile young.• population: a group of organisms belonging to the same species that live in the same area and interact with
one another• community: all of the populations of different species that live in the same area and interact with one another.• ecosystem: the living organisms (all the populations) in an area and the non-living aspects of the environment
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Summary
Practice
Use the resource below to answer the questions that follow.
• A Study in Stream Ecology at USGS http://gallery.usgs.gov/videos/449#.UKWeJId9KSo (6:57)
1. What are some of the abiotic factors that scientists monitor when dealing with stream ecosystems?2. What are some of the biotic factors that scientists monitor when dealing with stream ecosystems?3. What is a "benchmark" in ecology? Why are they essential?4. How does water pollution seem to be affecting diversity in some streams?
Review
1. What do ecologists study?2. What is an ecosystem?3. In a forest, what are five biotic factors present? Five abiotic factors?4. Define population. How is a population different from a community?
Missouri Standard(s):
• 4.1.A.a: Identify the biotic factors (populations of organisms) and abiotic factors (e.g., quantity of light andwater, range of temperatures, soil composition) that make up an ecosystem.
• 4.1.B.a: Identify populations within a community that are in competition with one another for resources• 4.1.B.b: Identify the factors that affect the number and types of organisms an ecosystem can support (e.g.,
food availability, abiotic factors such as quantity of light and water, temperature and temperature range, soilcomposition, disease, competitions from other organisms, predation)
• 4.1.B.c: Predict the possible effects of changes in the number and types of organisms in an ecosystem on thepopulations of other organisms within that ecosystem.
• 7.1.A.e: Recognize different kinds of questions suggest different kinds of scientific investigations (e.g., someinvolve observing and describing objects, organisms, or events; some involve collecting specimens; someinvolve experiments; some involve making observations in nature; some involve discovery of new objects andphenomena; some involve making models)
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1.2 Features of Populations and Growth Pat-terns
I can explore populations and the factors that affect population size.
What is a population?
When you think of the word population, you might think of the number of people in your town or city. But humansare not the only species to have populations. Every species has a population. Or many populations. This group ofpenguins, which are all members of the same species and all living together in the same space, is a population.
Populations
A population is a group of organisms of the same species, all living in the same area and interacting with eachother. Since they live together in one area, members of the same species reproduce together. Ecologists who studypopulations determine how healthy or stable the populations are. They also study how the individuals of a speciesinteract with each other and how populations interact with the environment.
Ecologists look at many factors that help to describe a population. First, ecologists can measure the number ofindividuals that make up the population, known as population size. They can then determine the population density,which is the number of individuals of the same species in an area. Population density can be expressed as numberper area, such as 20 mice/acre, or 50 rabbits/square mile.
Ecologists also study how individuals in a population are spread across an environment. This spacing of individualswithin a population is called dispersion. Some species may be clumped or clustered ( Figure 1.2) in an area. Othersmay be evenly spaced. Still others may be spaced randomly within an area.
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FIGURE 1.2Individuals within this population of purple loosestrife plants are clumpedbecause of the soil quality.Ecologists also study the birth and death ratesof the population. The birth rate is the number of births within a populationduring a specific time period. The death rate is the number of deaths withina population during a specific time period. Knowing the birth and deathrates of populations gives you information about a population’s health.For example, when a population is made up of mostly young organismsand the birth rate is high, the population is growing. A population withequal birth and death rates will remain the same size. Populations thatare decreasing in size have a higher death rate than birth rate.
Population Growth
What does population growth mean? You can probably guess that it means the number of individuals in a populationis increasing. The population growth rate tells you how quickly a population is increasing or decreasing. Whatdetermines the population growth rate for a particular population? One way the population of the United States hasgrown is through the movement of individuals into the United States from other parts of the world. The same effectscan be seen in wildlife populations. Individuals move into a population and increase its size. This is just one of themany factors affecting population growth. Of course, individuals may also move away from a population.
Births, Deaths, and Migration
Population growth rate depends on birth rates and death rates, as well as migration. First, we will consider the effectsof birth and death rates. You can predict the growth rate by using this simple equation: growth rate = birth rate –death rate.
If the birth rate is larger than the death rate, then the population grows. If the death rate is larger than the birth rate,what will happen to the population? The population size will decrease. If the birth and death rates are equal, thenthe population size will not change.
For an ecosystem to be stable, populations in that system must be healthy, and that usually means reproducing asmuch as their environment allows. Do organisms reproduce yearly or every few years? Do organisms reproduce formuch of their life, or just part of their life? Do organisms produce many offspring at once, or just a few, or even justone? Do many newborn organisms die, or do the majority survive? All these factors play a role in the growth of apopulation.
Migration is the movement of individual organisms into, or out of, a population. Migration affects populationgrowth rate. There are two types of migration:
1. Immigration is the movement of individuals into a population from other areas. This increases the populationsize and growth rate.
2. Emigration is the movement of individuals out of a population. This decreases the population size and growthrate.
One type of migration that you are probably familiar with is the migration of birds. Maybe you have heard that birdsfly south for the winter. In the fall, birds fly thousands of miles to the south where it is warmer. In the spring, they
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return to their homes. ( Figure below).
Monarch butterflies also migrate from Mexico to the northern U.S. in the summer and back to Mexico in the winter.These types of migrations move entire populations from one location to another.
FIGURE 1.3A flock of barnacle geese fly in formationduring the autumn migration.
Population Growth
In nature, organisms do not usually have ideal environments with unlimited food. In nature, there are limits.Sometimes, there will be plenty of food. Sometimes a fire will wipe out all of the available nutrients. Sometimes apredator will kill many individuals in a population. How do you think these limits affect the way organisms grow?
Usually, populations first grow rapidly while resources are abundant. Organisms are able to easily find food, waterand shelter. They are healthy and can reproduce. But as populations increase and resources become less available,organisms must compete for resources, mates, and space. Diseases spread more easily as populations grow andorganisms struggle to survive. Because of this competition, rates of growth slow down and slowly level off.
FIGURE 1.4What happened during the Irish Potato Famine? In the 1800s, a diseasecalled potato blight destroyed much of the potato crop in Ireland. Sincemany Irish people depended on potatoes as their staple food, massstarvation and emigration resulted. This caused Ireland’s population todramatically decrease. Lack of food is one factors that can limit populationgrowth.
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Limiting Factors to Population Growth
For a population to be healthy, factors such as food, nutrients, water and space, must be available. What happenswhen there are not resources to support the population? Limiting factors are resources or other factors in theenvironment that can lower the population growth rate. Limiting factors include a low food supply and lack ofspace. Limiting factors can lower birth rates, increase death rates, or lead to emigration.
When organisms face limiting factors, the population growth slows down. Competition for resources like food andspace cause the growth rate to stop increasing, so the population size levels off. This flat upper line on a growthcurve is the carrying capacity. The carrying capacity is the maximum population size that can be supported in aparticular area without destroying the habitat. Limiting factors determine the carrying capacity of a population.
FIGURE 1.5Curve A shows population growth whenthere are not limiting factors. Curve Bshows population growth when limitingfactors exist. Notice that the carryingcapacity is also shown.
Food Supply as Limiting Factor
If there are 12 hamburgers at a lunch table and 24 people sit down at a lunch table, will everyone be able to eat? Atfirst, maybe you will split hamburgers in half, but if more and more people keep coming to sit at the lunch table, youwill not be able to feed everyone. This is what happens in nature. But in nature, organisms that cannot get food willdie or find a new place to live. It is possible for any resource to be a limiting factor, however, a resource such as foodcan have dramatic consequences on a population.
In nature, when the population size is small, there is usually plenty of food and other resources for each individual.When there is plenty of food and other resources, organisms can easily reproduce, so the birth rate is high. As thepopulation increases, the food supply, or the supply of another necessary resource, may decrease. When necessaryresources, such as food, decrease, some individuals will die. Overall, the population cannot reproduce at the samerate, so the birth rates drop. This will cause the population growth rate to decrease.
When the population decreases to a certain level where every individual can get enough food and other resources,and the birth and death rates become stable, the population has leveled off at its carrying capacity.
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Other Limiting Factors
Other limiting factors include light, water, nutrients or minerals, oxygen, the ability of an ecosystem to recyclenutrients and/or waste, disease and/or parasites, temperature, space, and predation. Weather can also be a limitingfactor. Whereas most plants like rain, an individual cactus-like Agave Americana plant actually likes to grow whenit is dry. Rainfall limits reproduction of this plant which, in turn, limits growth rate.
Human activities can also limit the growth of populations. Such activities include use of pesticides, such as DDT,use of herbicides, and habitat destruction. Can you think of any other human activities that could limit populationgrowth?
FIGURE 1.6Does there have to be a winner? Whenanimals compete? Yes. Animals, or otherorganisms, will compete when both wantthe same thing. One must "lose" so thewinner can have the resource. But com-petition doesn’t necessarily involve physi-cal altercations.
Competition
Competition is a relationship between organisms that strive for the same resources in the same place. The resourcesmight be food, water, or space. There are two different types of competition:
1. Competition occurs between members of the same species. For example, two male birds of the same speciesmight compete for mates in the same area. This type of competition is a basic factor in natural selection. Itleads to the evolution of better adaptations within a species.
2. Competition occurs between members of different species. For example, predators of different species mightcompete for the same prey.
Competition often leads to extinction. The species that is less well adapted may get fewer of the resources that bothspecies need. As a result, members of that species are less likely to survive, and the species may go extinct.
Competing species sometimes evolve different adaptations. For example, they may evolve adaptations that allowthem to use different food sources. Figure below describes an example.
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FIGURE 1.7
Enrichment Practice I
Use this resource to answer the questions that follow.
• http://www.hippocampus.org/Biology → Non-Majors Biology→ Search: Interactions Within Communi-ties
1. What are the three general types of interactions within a community?2. Define competition.3. What are some of the resources organisms compete for?4. What is the main outcome of competition? (Hint: affects the niche)5. Describe an example of interspecific competition.6. Why might intraspecific competition occur?
Enrichment Practice II
• Competition at http://www.concord.org/activities/competition .
Video
Can be used as an introduction or a review.
• Biotic Potential at http://www.youtube.com/watch?v=BSVbdaubxxg (2:58)
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Vocabulary
• carrying capacity : Maximum population size that can be supported in a particular area without degradationof the habitat.
• migration : Movement of individual organisms into, or out of, a population.• population: Group of organisms belonging to the same species that live in the same area and interact with
one another.• population size: Number of individuals of a population.• limiting factor: Factors in the environment that can lower the population growth rate.
Summary
FIGURE 1.8Can you summarize the information in this section in the box above?
Review
1. Would all the deer and mice living in a forest be a population? Why or why not?2. What factors affect population growth?3. What is a limiting factor?4. What are three examples of limiting factors?5. What is competition?
Missouri Standard(s):
• 4.1.B.a: Identify populations within a community that are in competition with one another for resources• 4.1.B.b: Identify the factors that affect the number and types of organisms an ecosystem can support (e.g.,
food availability, abiotic factors such as quantity of light and water, temperature and temperature range, soilcomposition, disease, competitions from other organisms, predation)
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• 4.1.B.c: Predict the possible affects of changes in the number and types of organisms in an ecosystem on thepopulations of other organisms within that ecosystem
• 4.3.C.a: Relate examples of adaptations (specialized structures or behaviors) within a species to its abil-ity to survive in a specific environment (e.g. hollow bones/flight, hollow hair/insulation, dense root struc-ture/compact soil, seeds/food, protection for plant embryo vs. spores, fins/movement in water)
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1.3 References
1. . The Great Barrier Reef is an example of a marine ecosystem.2. . The Great Barrier Reef is an example of a marine ecosystem.3. Image copyright dabjola, 2012. .4. . Organisms show exponential growth in the absence of limiting factors, while they show logistic growth in
the presence of limiting factors.5. . Organisms show exponential growth in the absence of limiting factors, while they show logistic growth in
the presence of limiting factors.6. . Specialization lets ground anoles and tree anoles live together without competing.7. . Specialization lets ground anoles and tree anoles live together without competing.
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CHAPTER 2 Energy FlowChapter Outline
2.1 PRODUCERS, CONSUMERS, AND DECOMPOSERS
2.2 ENERGY FLOW IN AN ECOSYSTEM
2.3 REFERENCES
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2.1 Producers, Consumers, and Decomposers
• I can explain where all the energy in an ecosystem comes from.
• I can classify organisms on the basis of how they obtain energy and describe examples of each.
Ecosystems need energy. Many ecosystems get their energy in the form of sunlight, which enters the ecosystemthrough photosynthesis. This energy then flows through the ecosystem, passed from producers to consumers.Plants are producers in many ecosystems. Energy flows from plants to the herbivores that eat the plants, and then tocarnivores that eat the herbivores. The flow of energy depicts interactions of organisms within an ecosystem.
For example, bears get their energy from their food. Brown bears eat a varied diet, from nuts and berries to fishand other animals. When bears eat a berry, they are obtaining energy that the plant originally captured from thesun. Even when a bear eats another animal, the energy in that animal ultimately came from eating a producer thatcaptured the sun’s energy.
Energy is the ability to do work. In organisms, this work can be physical work, like walking or jumping, or it canbe the work used to carry out the chemical processes in their cells. Every biochemical reaction that occurs in anorganism’s cells needs energy. All organisms need a constant supply of energy to stay alive.
Some organisms can get the energy directly from the sun. Other organisms get their energy from other organisms.Through predator-prey relationships, the energy of one organism is passed on to another. That is, the energy of theprey is passed on to the predator that consumed it. Energy is constantly flowing through a community. With just afew exceptions, all life on Earth depends on the sun’s energy for survival.
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Producers and Photosynthesis
The energy of the sun is first captured by producers ( Figure 2.1), organisms that can make their own food. Manyproducers make their own food through the process of photosynthesis. Photosynthesis is the process plants use tomake their own “food” from the sun’s energy, carbon dioxide and water. The "food" the producers make is the sugar,glucose.
During photosynthesis, carbon dioxide and water combine, and using solar energy, create glucose and oxygen.Scientists represent this reaction in the following way:
carbon dioxide (CO2) + water (H2O) –>sugar (glucose) + oxygen (O2)
Glucose is a sugar that acts as the "food" source for plants. Oxygen, which is necessary for animal life, is the waste ofphotosynthesis. Essentially, these producers are changing the energy from the sunlight into a usable form of energy.They are also making the oxygen that we breathe. Oxygen is a waste product of photosynthesis.
The Photosynthesis Song can be heard at http://www.youtube.com/watch?v=C1_uez5WX1o (1:52).
Producers make food for themselves, as well as the rest of the ecosystem. As energy is not recycled, energy mustconsistently be captured by producers. This energy is then passed on to the organisms that eat the producers, andthen to the organisms that eat those organisms, and so on.
Actually, almost all organisms obtain their energy from photosynthetic organisms. For example, if a bird eats acaterpillar, then the bird gets the energy that the caterpillar got from the plants it ate. So the bird is indirectly gettingenergy that began with the “food” formed through photosynthesis that occurred in the plant. Therefore, the processof photosynthesis is central to sustaining life on Earth.
The survival of every ecosystem is dependent on the producers. Without producers capturing the energy from the sunand turning it into glucose, an ecosystem could not exist. On land, plants are the dominant producers. Phytoplankton,tiny photosynthetic organisms, are the most common producers in the oceans and lakes. Algae, which is the greenlayer you might see floating on a pond, are an example of phytoplankton.
There are also bacteria that use chemical processes to produce food. They get their energy from sources other thanthe sun, but they are still called producers. This process is known as chemosynthesis, and is common in ecosystemswithout sunlight, such as certain marine ecosystems.
FIGURE 2.1Producers include (a) plants, (b) algae, and (c) phytoplankton.
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FIGURE 2.2Notice how this leaf is slowly being brokendown. This process can be carried out byfungi and bacteria on the ground. Break-ing down old leaves is an important pro-cess since it releases the nutrients, likecarbon and nitrogen, in the dead leavesback into the soil for living plants to use.
Consumers
Recall that producers make their own food through photosynthesis. But many organisms are not producers andcannot make their own food. So how do these organisms obtain their energy? They must get their energy fromother organisms. They must eat other organisms, or obtain their energy from these organisms some other way. Theorganisms that obtain their energy from other organisms are called consumers. All animals are consumers, andthey eat other organisms. Fungi and many protists and bacteria are also consumers. But, whereas animals eat otherorganisms, fungi, protists, and bacteria "consume" organisms through different methods.
The consumers can be placed into different groups, depending on what they consume.
• Herbivores are animals that eat producers to get energy. For example, rabbits and deer are herbivores thateat plants. The caterpillar pictured below ( Figure below) is a herbivore. Animals that eat phytoplankton inaquatic environments are also herbivores.
• Carnivores feed on animals, either herbivores or other carnivores. Snakes that eat mice are carnivores. Hawksthat eat snakes are also carnivores ( Figure below).
• Omnivores eat both producers and consumers. Most people are omnivores, since they eat fruits, vegetables,and grains from plants, and also meat and dairy products from animals. Dogs, bears, and raccoons are alsoomnivores.
FIGURE 2.3Consumers can be both herbivores likethe caterpillar (a) or carnivores like thehawk (b)
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Predation
Predation is a relationship in which members of one species (the predator) consume members of another species(the prey). The lionesses and zebra in Figure below are classic examples of predators and prey. In addition to thelionesses, there is another predator in this figure. Can you spot it? The other predator is the zebra. Like the lionesses,it consumes prey species, in this case species of grass. However, unlike the lionesses, the zebra does not kill its prey.Predator-prey relationships such as these account for most energy transfers in food chains and food webs.
FIGURE 2.4Predators and Their Prey: These li-onesses feed on the carcass of a zebra
Decomposers
Decomposers ( Figure below) get nutrients and energy by breaking down dead organisms and animal wastes.Through this process, decomposers release nutrients, such as carbon and nitrogen, back into the environment. Thesenutrients are recycled back into the ecosystem so that the producers can use them. They are passed to other organismswhen they are eaten or consumed. Many of these nutrients are recycled back into the soil, so they can be taken upby the roots of plants.
The stability of an ecosystem depends on the actions of the decomposers. Examples of decomposers includemushrooms on a decaying log. Bacteria in the soil are also decomposers. Imagine what would happen if therewere no decomposers. Wastes and the remains of dead organisms would pile up and the nutrients within the wasteand dead organisms would not be released back into the ecosystem. Producers would not have enough nutrients. Thecarbon and nitrogen necessary to build organic compounds, and then cells, allowing an organism to grow, would beinsufficient. Other nutrients necessary for an organism to function properly would also not be sufficient. Essentially,many organisms could not exist.
Examples of decomposers are (a) bacteria and (b) fungi.
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Vocabulary
• energy: Ability to do work.• photosynthesis: Process by which specific organisms (including all plants) use the sun’s energy to make their
own food from carbon dioxide and water; process that converts the energy of the sun, or solar energy, intocarbohydrates, a type of chemical energy.
• predator-prey relationship: Interaction between two organisms of unlike species; one organism acts aspredator that captures and feeds on the other organism, which serves as the prey.
• producer: Organism that produces food (glucose) for itself and other organisms.• consumer: Organism that must consume other organisms to obtain food for energy.• decomposer: Organism that obtains nutrients and energy by breaking down dead organisms and animal
wastes.
Summary
Practice I
Use the resource below to answer the questions that follow:
Producers and Consumers at http://www.youtube.com/watch?v=P0a97kS_3SA (1:59)
1. Can producers function without sunlight? Why or why not?2. What are some examples of producers? Why are they called autotrophs?3. How do some producers use sunlight to make "food"? What other resources do they require?
Practice II
Use the resource below to answer the questions that follow:
Decomposers at http://www.youtube.com/watch?v=Z6V0a_7N1Mw (3:19)
1. What is the role of decomposers in an ecosystem? What is the source of the matter which is decomposed?2. How do the actions of earthworms improve soil quality? How does this impact the amount of biomass an
ecosystem can support?3. How do gastropods function as decomposers?
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Review
1. Where does all the "food" in an ecosystem ultimately come from?
2. What is required for photosynthesis to occur? What is made during photosynthesis?
3. Why are producers important to an ecosystem?
4. What is a consumer?
5. What’s the term for a consumer that eats both leaves and fish?
6. What are the different types of consumers?
7. Why are decomposers important in the ecosystem?
Missouri Standard(s):
• 1.2.C.b: Recognize and apply the fact that energy from the Sun is the source of almost all energy used toproduce the food for living organisms
• 4.2.A.a: Diagram and describe the transfer of energy in an aquatic food web and a land food web withreference to producers, consumers, decomposers, scavengers, and predator/prey relationships
• 4.2.A.b: Classify populations of unicellular and multicellular organisms as producers, consumers, and decom-posers by the role they serve in the ecosystem
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2.2 Energy Flow in an Ecosystem
I can diagram and describe the transfer of energy in an ecosystem.
How do the grasshopper and the grass interact?
Grasshoppers don’t just hop on the grass. They also eat the grass. Other organisms also eat the grass, and someanimals even eat the grasshopper. These interactions can be visualized by drawing a food web, which will show allthe feeding relationships in that ecosystem.
Food Chains and Webs
Energy must constantly flow through an ecosystem for the system to remain stable. What exactly does this mean?Essentially, it means that organisms must eat other organisms. Remember that all but a small amount of energy startswith the sun and then is transferred to producers through photosynthesis. Consumers who eat the producers then passon energy to other consumers. Food chains show the eating patterns in an ecosystem. Food energy flows from oneorganism to another. Arrows are used to show the feeding relationship between the animals. The arrow points fromthe organism being eaten to the organism that eats it. For example, an arrow from a plant to a grasshopper showsthat the grasshopper eats the leaves. Energy and nutrients are moving from the plant to the grasshopper. Rememberit this way: ’The arrows show the energy flow’. Next, a bird might prey on the grasshopper, a snake may eat the bird,and then an owl might eat the snake. The food chain would be:
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plant→ grasshopper→ bird→ snake→ owl.
A food chain cannot continue to go on and on. For example the food chain could not be:
plant→ grasshopper→ spider→ frog→ lizard→ fox→ hawk.
Food chains only have 4 or 5 total levels. Therefore, a chain has only 3 or 4 levels for energy transfer to consumers.Why do you think that is? The figure below represents the total energy the grasshopper received from the plant. Usethe graph and the caption information to formulate your answer.
FIGURE 2.5Think it through: Only 10% of the original energy from the plant is storedin the grasshoppers body. The rest is used to carry out daily functions orwasted (released as heat). So when the bird eats the grasshopper, is hegetting all the energy the grasshopper got from the plant? What about thesnake? How much of the plants energy would he be receiving?
FIGURE 2.6This food chain includes producers andconsumers. How could you add decom-posers to the food chain?
In an ocean ecosystem, one possible food chain might look like this: phytoplankton → krill → fish → shark.The producers are always at the beginning of the food chain, bringing energy into the ecosystem. Throughphotosynthesis, the producers create their own food in the form of glucose, but also create the food for the otherorganisms in the ecosystem. The herbivores come next, then the carnivores. When these consumers eat otherorganisms, they use the glucose in those organisms for energy. In this example, phytoplankton are eaten by krill,which are tiny, shrimp-like animals. The krill are eaten by fish, which are then eaten by sharks. Could decomposersbe added to a food chain?
Each organism can eat and be eaten by many different types of organisms, so simple food chains are rare in nature.Since most animals eat a variety of food, a food chain does not really give us enough information about an ecosystem.Ecologists often show the feeding relationships between animals as food webs. A food web is a better way ofshowing the feeding relationships between all of the organisms living in the community. A food web shows manymore arrows, but still shows the flow of energy. A complete food web may show hundreds of different feedingrelationships.
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FIGURE 2.7Food web in the Arctic Ocean.
FIGURE 2.8If the cheetah is successful in capturingthe warthog, it would gain some energyby eating it. But would the cheetah gainas much energy as the warthog has everconsumed? No, the warthog has used upsome of the energy it has consumed forits own needs. The cheetah will only gaina fraction of the energy that the warthoghas consumed throughout its lifetime.
Energy Pyramids
When an herbivore eats a plant, the energy in the plant tissues is used by the herbivore. But how much of thatenergy is transferred to the herbivore? Remember that plants are producers, bringing the energy into the ecosystemby converting sunlight into glucose. Does the plant use some of the energy for its own needs? Recall the energy isthe ability to do work, and the plant has plenty or "work" to do. So of course it needs and uses energy. After the plantuses the energy from glucose for its own needs, the excess energy is available to the organism that eats the plant.
The herbivore uses the energy from the plant to power its own life processes and to build more body tissues. However,only about 10% of the total energy from the plant gets stored in the herbivore’s body as extra body tissue. The rest ofthe energy is used by the herbivore and released as heat. The next consumer on the food chain that eats the herbivorewill only store about 10% of the total energy from the herbivore in its own body. This means the carnivore will storeonly about 1% of the total energy that was originally in the plant. In other words, only about 10% of energy of onestep in a food chain is stored in the next step in the food chain. The majority of the energy is used by the organismor released to the environment.
Every time energy is transferred from one organism to another, there is a loss of energy. This loss of energy can be
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shown in an energy pyramid. An example of an energy pyramid is pictured below. Since there is energy loss ateach step in a food chain, it takes many producers to support just a few carnivores in a community (which makessense because aren’t pyramids largest at the bottom!).
Each step of the food chain in the energy pyramid is called a trophic level. Plants or other photosyntheticorganisms are found on the first trophic level, at the bottom of the pyramid. The next level up will be the herbivores,and then the carnivores that eat the herbivores. The energy pyramid shows four levels of a food chain, from producersto carnivores. Because of the high rate of energy loss in food chains, there are usually only 4 or 5 trophic levels inthe food chain or energy pyramid. There just is not enough energy to support any additional trophic levels.
FIGURE 2.9As illustrated by this ecological pyramid,it takes a lot of phytoplankton to supportthe carnivores of the oceans. This energypyramid has four trophic levels, which sig-nify the organisms’ place in the food chainfrom the original source of energy.
Vocabulary
• consumer: Organism that must consume other organisms to obtain food for energy.• decomposer: Organism that obtains nutrients and energy by breaking down dead organisms and animal
wastes.• food chain: Diagram that shows feeding interactions in an ecosystem through a single pathway.• food web: Diagram that shows feeding interactions between many organisms in an ecosystem through multi-
ple intersecting pathways.• producer: Organism that produces food for itself and other organisms.• energy: Ability to do work.• energy pyramid: Diagram showing how energy decreases from lower to higher trophic levels.
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Summary
Practice I
Use the resource below to answer the questions that follow.
Build A Food Web at http://www.sciencesource2.ca/resources/SS_active_art/active_art/SEinteractive_gr09_ch01_pg31/index.html
1. What do the Loons and Arctic Tern have in common in the food web?2. What do the Beluga and the sea duck have in common in the food web?3. What species in the food web feed on zooplankton (animal plankton)?4. When you build your own food web what must it contain to be healthy? How many healthy food webs could
you build?
Practice II
Use the resource below to answer the questions that follow.
Ecological Pyramids at http://www.youtube.com/watch?v=NJplkrliUEg (4:03)
1. What are three types of ecological pyramids? How do their shapes compare?2. Do you think it would be possible to construct a pyramid where the number of carnivores was more than the
number of herbivores? Why or why not?3. Do you think it would be possible to construct a pyramid where the biomass of carnivores was more than the
biomass of herbivores? How does this compare to a numbers pyramid.
What consumes energy at each trophic level? How does this contribute to energy loss between trophic levels?
Review
1. What is the difference between a food chain and a food web?2. Food chains always begin with what type of organism? Why?3. What is the herbivore in the following food chain: algae ->fish ->herons?4. When an herbivore eats a plant, what happens to 90% of the energy obtained from that plant?5. What is a trophic level?6. In a forest community, caterpillars eat leaves, birds eat caterpillars and snakes eat birds. Draw an energy
pyramid using this information.
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Missouri Standard(s):
• 4.2.A.a: Diagram and describe the transfer of energy in an aquatic food web and a land food web withreference to producers, consumers, decomposers, scavengers, and predator/prey relationships
• 4.2.A.b: Classify populations of unicellular and multicellular organisms as producers, consumers, and decom-posers by the role they serve in the ecosystem
• 1.2.C.b: Recognize and apply the fact that energy from the Sun is the source of almost all energy used toproduce the food for living organisms
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2.3 References
1. (a) Jan Tik; (b) Flickr:qorize; (c) Courtesy of Prof. Gordon T. Taylor, Stony Brook University/NSF PolarPrograms. Producers include plants, algae, and diatoms.
2. . Bacteria (a) and fungi (b) are often decomposers.3. Mariana Ruiz Villarreal (LadyofHats) for CK-12 Foundation. This food chain includes both producers and
consumers, but not decomposers.4. Laura Guerin. This food web displays some feeding relationships found in the Arctic Ocean. CC BY-NC 3.05. . This energy pyramid illustrates that many organisms on the bottom are needed to support the top carnivores.6. . This energy pyramid illustrates that many organisms on the bottom are needed to support the top carnivores.
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CHAPTER 3 Adaptations and Evolutionof Populations
Chapter Outline3.1 ADAPTATION
3.2 REFERENCES
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3.1 Adaptation
I can understand adaptations in organisms ensure survival as natural environments change.
Why would an organism match its background? Wouldn’t it be better to stand out?
An organism that blends with its background is more likely to avoid predators. If it survives, it is more likely to haveoffspring. Those offspring are more likely to blend into their backgrounds. This butterfly appears to be well adaptedto its environment. It is less likely to be eaten by a bird than a butterfly that stands out against the tree.
Adaptation
The special characteristics that enable plants and animals to be successful in a particular environment are called adap-tations. All organisms have adaptations that help them survive and thrive. Some adaptations are structural. Structuraladaptations are physical features of an organism like the bill on a bird, pads on a camels feet or the fur on a bear.Other adaptations are behavioral. Behavioral adaptations are the things organisms do to survive. For example,
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bird calls and migration are behavioral adaptations, as well as, an opossum playing "dead" for protection from hisenemies.
Adaptations are the result of evolution. Evolution is a change in a species over long periods of time. Fossils of dif-ferent organisms have been discovered that have helped scientists track structural changes in organisms. Adaptationsusually occur because a gene changes by accident (or mutates)! Some mutations can help an animal or plant survivebetter than others in the species.
For example, imagine a bird species. One day a bird is born with a beak that is longer than the beak of other birdsin the species. The longer beak helps the bird catch more food. Because the bird can catch more food, it is healthierthan the other birds, lives longer and breeds (reproduces) more. The bird passes the gene for a longer beak on toits offspring. They also live longer and have more offspring and the gene continues to be inherited generation aftergeneration. Eventually the longer beak can be found in all of the species. This doesn’t happen overnight. It takesthousands of years for a mutation to be found in an entire species.
Here is another example. Think about a population of oak trees. Imagine that a fungus has arrived from Asia to NorthAmerica. Most of the North American oak trees are killed by the fungus. But a few oak trees have a mutation thatallows them to survive the fungus. Those oak trees are better adapted to the new environment than the others. Thosetrees have a better chance of surviving. They will probably reproduce. The trees may pass on the favorable mutationto their offspring. The other trees will die because they can not survive the fungus. Eventually, the population of oaktrees will change. Most of the trees will have the trait to survive the fungus.
Over time, organisms that are better adapted to their environment survive and breed. Organisms that are not welladapted to an environment may not survive. The characteristics that help a species survive in an environment arepassed on to future generations. Those characteristics that don’t help the species survive slowly disappear.
VIDEO: The Making of the Fittest: Natural Selection http://www.youtube.com/watch?v=wrTXvrKBlbc
Different types of Adaptations
Camouflage, as in a toad’s ability to blend in with its surroundings, is a common example of an adaptation. Thecombination of bright orange and black on a monarch butterfly is an adaptation to warn potential predators thatthe butterfly is poisonous and prevent it from being eaten. These special features have evolved over long periodsof time, through the process of natural selection. Adaptations afford the organism a better chance to survive in itssurroundings.
Desert Adaptations Deserts, where the environment is generally hot and extremely dry, provide many strikingexamples of how plants and animals are adapted to their surroundings. The two main adaptations that desert animalsmust make are how to deal with lack of water and how to deal with extremes in temperature. Plants have manyadaptations to cope with the lack of water. Some desert plants, such as the barrel cactus, have expandable stemsfor storing water. Other plants have adaptations that reduce water loss from their leaves, the part of a plant throughwhich most of the water is lost. Still others have a waxy coating on the leaves, or have small leaves, that reducethe surface area exposed to the drying elements. In many cases, desert plants have no leaves at all. Photosynthesis,which normally occurs in green leaves, is carried out in the stems, which are themselves green with the pigmentchlorophyll.
Many desert animals avoid the heat of the desert by simply staying out of it as much as possible and prevent waterleaving their bodies in a number of different ways. Some, like kangaroo rats and lizards, live in burrows which donot get too hot or too cold and have more humid (damp) air inside. These animals stay in their burrows during thehot days and emerge at night to feed, making them nocturnal.
Other animals have bodies designed to save water. Scorpions and wolf spiders have a thick outer covering whichreduces moisture loss. The kidneys of desert animals concentrate urine, so that they excrete less water. The kangaroorat conserves water by excreting a solid urine rather than liquid.
Tropical Rainforest Adaptations In sharp contrast, the climate of the tropical rainforest is hot and wet. With over
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FIGURE 3.1Cacti have thick, water-retaining bodies that help them conserve water.
FIGURE 3.2The creosote [kree-uh-soht] bush is adesert-dwelling plant that produces toxinsthat prevent other plants from growingnearby, thus reducing competition for nu-trients and water.
80 inches of rain per year, as opposed to the desert’s 10 inches or less, plants have adaptations that enable them toshed water efficiently. The leaves of many rainforest plants have drip tips for this purpose. Buttress and stilt rootsare thought to provide extra support for trees growing in spongy, wet soils.
Tropical rainforest plants also have adaptations to take in what little sunlight is available on the dark forest floor.Large leaves are common; they increase the amount of sunlight a plant can capture. Other plants, like orchids,bromeliads and ferns, grow as epiphytes high up in the canopy where there is more sunlight.
Other Adaptations The adaptations discussed above are all adaptations to specific climatic conditions, but organ-isms have also developed adaptations to other aspects of their environment. Some animals have adapted to eat acertain type of food; others have adapted to avoid being eaten themselves. Most animals have behavioral adaptationswhich help them attract a mate. In the plant world, many flowers have evolved specific structures that help ensurepollination by the insects they attract.
Many adaptations protect organisms from the external environment. Cacti (plural form of cactus) have water-retaining bodies to store as much water as possible in dry conditions and have needles to protect them from predators(which includes those after only its water!). Other adaptations help an organism move or gather food. Reindeer havesponge-like hooves that help them walk on snowy ground without slipping and falling. Fish at the bottom of theocean are tiny and use very little energy because there is very little food. Organisms have special features that helpthem avoid being eaten. Some plants have poisonous or foul-tasting substances in them that keep animals fromeating them. Their brightly colored flowers serve as a warning. The same is true of some frogs, which can bepoisonous, as well .
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FIGURE 3.3Poison dart frogs have toxins in their skin. Their bright colors warnpotential predators not to take a bite!
FIGURE 3.4Mimicry of leaves by insects is an adaptation for evading predators. Thisexample is a katydid from Costa Rica.
FIGURE 3.5This flower is from an aloe plant. Aloesare succulent plants, which have adap-tations that allow them to store water intheir enlarged fleshy leaves, stems, orroots. This allows them to survive in aridenvironments.
Plant Adaptations
Plants live just about everywhere on Earth. To live in so many different habitats, they have evolved adaptations thatallow them to survive and reproduce under a diversity of conditions.
All plants are adapted to live on land. Or are they? All living plants today have terrestrial ancestors, but some plantsnow live in the water. They have had to evolve new adaptations for their watery habitat.
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Adaptations to Water
Aquatic plants are plants that live in water. Living in water has certain advantages for plants. One advantage is,well, the water. There’s plenty of it and it’s all around. Therefore, most aquatic plants do not need adaptationsfor absorbing, transporting, and conserving water. They can save energy and matter by not growing extensive rootsystems, vascular tissues, or thick cuticles on leaves. Support is also less of a problem because of the buoyancy ofwater. As a result, adaptations such as strong woody stems and deep anchoring roots are not necessary for mostaquatic plants.
Living in water does present challenges to plants, however. For one thing, pollination by wind or animals isn’tfeasible under water, so aquatic plants may have adaptations that help them keep their flowers above water. Forinstance, water lilies have bowl-shaped flowers and broad, flat leaves that float. This allows the lilies to collectthe maximum amount of sunlight, which does not penetrate very deeply below the water’s surface. Plants that livein moving water, such as streams and rivers, may have different adaptations. For example, cattails have narrow,strap-like leaves that reduce their resistance to the moving water (see Figure below).
FIGURE 3.6Water lilies and cattails have differentadaptations for life in the water. Comparethe leaves of the two kinds of plants. Howdo the leaves help the plants adapt to theirwatery habitats?
Adaptations to Extreme Dryness
Plants that live in extremely dry environments have the opposite problem: how to get and keep water. Plants thatare adapted to very dry environments are called xerophytes. Their adaptations may help them increase water intake,decrease water loss, or store water when it is available.
The saguaro cactus pictured in Figure below has adapted in all three ways. When it was still a very small plant, justa few inches high, its shallow roots already reached out as much as 2 meters (7 feet) from the base of the stem. Bynow, its root system is much more widespread. It allows the cactus to gather as much moisture as possible from rarerainfalls. The saguaro doesn’t have any leaves to lose water by transpiration. It also has a large, barrel-shaped stemthat can store a lot of water. Thorns protect the stem from thirsty animals that might try to get at the water inside.
Adaptations to Air
Plants called epiphytes grow on other plants. They obtain moisture from the air and make food by photosynthesis.Most epiphytes are ferns or orchids that live in tropical or temperate rainforests (see Figure below). Host treesprovide support, allowing epiphyte plants to obtain air and sunlight high above the forest floor (think of it as beingon someones shoulders!). Being elevated above the ground lets epiphytes get out of the shadows on the forest floorso they can get enough sunlight for photosynthesis. Being elevated may also reduce the risk of being eaten byherbivores and increase the chance of pollination by wind.
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FIGURE 3.7The saguaro cactus has many adapta-tions for extreme dryness. Can you listsome?
FIGURE 3.8These Elkhorn and Staghorn ferns are growing on a rainforest tree asepiphytes.
Epiphytes don’t grow in soil, so they may not have roots. However, they still need water for photosynthesis.Rainforests are humid, so the plants may be able to absorb the water they need from the air. However, manyepiphytes have evolved modified leaves or other structures for collecting rainwater, fog, or dew. The leaves of thebromeliad shown in Figure below are rolled into funnel shapes to collect rainwater. The base of the leaves forms atank that can hold more than 8 liters (2 gallons) of water! Some insects and amphibians may spend their whole lifecycle in the pool of water in the tank, adding minerals to the water with their wastes. The tissues at the base of theleaf are absorbent, so they can take in both water and minerals from the tank.
The Fossil Record
Fossils are the preserved remains of animals, plants and other organisms from the distant past. Examples of fossilsinclude bones, teeth, and impressions. By studying fossils, evidence for evolution is revealed. Paleontologists are
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FIGURE 3.9The leaves of this bromeliad are adapted to collect, store and absorbrainwater.
FIGURE 3.10This rock contains a portion of a fossilizedtree fern. Scientists study fossils of plants,animals, and other organisms in order tobetter understand what life was like onEarth many years ago and how it haschanged over time. Fossils are importantevidence for the theory of evolution.
scientists who study fossils to learn about life in the past. Paleontologists compare the features of species fromdifferent periods in history. With this information, they try to understand how species have evolved over millions ofyears (Figure 3.9).
Until recently, fossils were the main source of evidence for evolution ( Figure 3.10). Through studying fossils, wenow know that today’s organisms look much different in many cases than those that were alive in the past. Scientistshave also shown that organisms were spread out differently across the planet. Earthquakes, volcanoes, shifting seas,and other movements of the continents have all affected where organisms live and how they adapted to their changingenvironments.
Rock Layers and the Age of Fossils
There are many layers of rock in the Earth’s surface. Newer layers form on top of the older layers. Therefore, youcan tell how old a fossil is by observing in which layer of rock it was found. The fossils and the order in whichfossils appear is called the fossil record. The fossil record provides evidence for when organisms lived on Earth,how species evolved, and how some species have gone extinct. Geologists use a method called radiometric dating
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FIGURE 3.11Evolution of the horse. Fossil evi-dence, depicted by the skeletal frag-ments, demonstrates evolutionary mile-stones in this process. Notice the 57million year evolution of the horse legbones and teeth. Especially obvious isthe transformation of the leg bones fromhaving four distinct digits to that of today’shorse.
to determine the exact age of rocks and fossils in each layer of rock. This technique measures how much of theradioactive materials in each rock layer have broken down ( Figure below).
Radiometric dating has been used to determine that the oldest known rocks on Earth are between 4 and 5 billionyears old. The oldest fossils are between 3 and 4 billion years old. Remember that during Darwin’s time, peoplebelieved the Earth was just about 6,000 years old. The fossil record proves that Earth is much older than people oncethought.
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FIGURE 3.12About 25 to 40 million years ago these in-sects were trapped in a gooey substance,called resin, that comes from trees. Thefossils in the movie Jurassic Park weretrapped in resin!
FIGURE 3.13This device, called a spectrophotometer,can be used to measure the level ofradioactive decay of certain elements inrocks and fossils to determine their age.
Vocabulary
• Adaptation: Trait that an organism inherits that helps it survive in its natural environment.• Mutation: Change in the genetic makeup of a population of organisms that can be beneficial, harmful, or
neutral.• fossil: Preserved part of animals, plants, and other organisms from the distant past.• fossil record: Complete set of fossils that has been discovered, and the order in which the fossils appear.
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Summary
Practice
Use the resources below to answer the questions that follow.
Practice I
James Hagadorn, Paleontologist: Traces of Early Animal Life at http://shapeoflife.org/video/james-hagadorn-paleontologist-traces-early-animal-life (6:11)
1. Why is it believed the first animals left no fossilized bones?2. What do paleontologists look for when they search for evidence of early organisms?3. How old are the geologic deposits Dr. Hagadorn is searching? How old is the evidence he has found for the
first mobile organisms?4. What does the ability to hunt others do to the fossil record? Why?
Practice II
Jenny Clack, Paleontologist: The First Vertebrate Walks on Land at http://shapeoflife.org/video/jenny-clack-paleontologist-first-vertebrate-walks-land (7:04)
1. What is a "tetrapod"? What question do paleontologists hope they can answer by studying them?2. What is special about "Boris"?
Practice III
Richard Dawkins: Show me the intermediate fossils! at http://www.youtube.com/watch?v=o92x6AvxCFg (2:34)
1. What evidence is there that modern whales once had hindlimbs?2. Pakicetus and Rodhocetus are considered to be ancestors of modern whales. Scientists still argue about how
aquatic Pakicetus was, but Rodhocetusis considered to be a largely aquatic animal.
a. Where is the nostril located on Pakicetus?b. Where is the nostril located on Rodhocetus?c. What is the relationship in time between these two species?
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3. What modern animal is most closely related to modern whales? What is the evidence? In what kind ofenvironment does this modern relation live?
Opportunity for Enrichment:
Use the resource below to answer the questions that follow.
• How Do Organisms Adapt to their Environment? http://www.bbc.co.uk/schools/gcsebitesize/science/edexcel/classification_inheritance/variationrev1.shtml
1. What is variation?2. Why do organisms in different habitats need different adaptation?3. How have polar bears adapted to their environment?4. How have snowshoe hares adapted to their environment?5. How have arctic plants adapted to the environment?
Review
1. How do adaptations develop?2. What does it mean to say that an organism is well adapted to its environment?3. What is a mutation?4. List special challenges that aquatic plants face.5. What are xerophytes? Give an example.6. Identify three general ways that plants can adapt to extreme dryness.7. Describe how epiphytes can absorb moisture without growing roots in soil.8. What is a fossil? Give three examples.9. What has the fossil record revealed about life on Earth?
10. How does radioactive dating work?11. What is radioactive dating used for?
Resource for Review
Quick read: http://www.durrell.org/library/Document/adaptation.pdf
Missouri Standard(s):
• 4.3.C.a: Relate examples of adaptations (specialized structures or behaviors) within a species to its abil-ity to survive in a specific environment (e.g., hollow bones/flight, hollow hair/insulation, dense root struc-ture/compact soil, seeds/food, protection for plant embryo vs. spores, fins/movement in water)
• 4.3.C.b: Predict how certain adaptations, such as behavior, body structure, or coloration, may offer a survivaladvantage to an organism in a particular environment
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3.2 References
1. Adrian Pingstone (Wikimedia: Arpingstone). Brightly colored poison dart frogs have toxins in their skin.Public Domain
2. . Water lilies and cattail adaptations.3. . Water lilies and cattail adaptations.4. . Saguaro cactus adaptations.5. . Saguaro cactus adaptations.6. . Elkhorn and Staghorn ferns.7. . Elkhorn and Staghorn ferns.8. . Bromeliad rainwater collecting leaves.9. . Bromeliad rainwater collecting leaves.
10. . Insects trapped in tree resin, or amber.11. . Insects trapped in tree resin, or amber.12. . Image of a spectrophotometer.13. . Image of a spectrophotometer.
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CHAPTER 4 Environmental FactorsChapter Outline
4.1 IMPORTANCE OF BIODIVERSITY
4.2 HUMAN CAUSES OF EXTINCTION
4.3 OUTDOOR AIR POLLUTION
4.4 SOURCES OF WATER POLLUTION
4.5 HABITAT DESTRUCTION
4.6 REDUCE, REUSE, AND RECYCLE
4.7 REFERENCES
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4.1 Importance of Biodiversity
I can understand the importance of biodiversity in a healthy ecosystem.
FIGURE 4.1Coral reefs are one of the biomes with the highest biodiversity on Earth.
A place such as a coral reef has many different species of plants and animals. That means the coral reef is aecosystem with high biodiversity. Because of its biodiversity, the rainforest shown above is an ecosystem withextreme importance. Why is biodiversity so important? The main reason is to maintain the health and stability ofthe ecosystem.
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Importance of Biodiversity
Biodiversity is a measurement of the amount of variation of the species in a given area. More specifically, biodi-versity can be defined as the variety of life and its processes, including the variety of living organisms, the geneticdifferences among them, and the communities and ecosystems in which they occur.
Extinction is a threat to biodiversity. Does it matter if we are losing thousands of species each year? The answeris yes. It matters even if we consider not only the direct benefits to humans, but also the benefits to the ecosystems.The health and survival of ecosystems is related to that ecosystem’s biodiversity.
Biodiversity has many benefits to ecosystems. High biodiversity makes ecosystems more stable. What can happento an ecosystem if just one species goes extinct? What if that one species was a producer or decomposer? Wouldthe loss of a producer have an effect on all the organisms that relied on that producer? If a decomposer vanishes, arethere other decomposers to fill the void? Maybe the resulting species will adapt. Other species may fill in the nicheleft by the extinct species. But the extinction of one species could have a "domino" effect, resulting in the extinctionof other species. This could greatly effect the stability of the whole ecosystem. It is helpful to think of an ecosystemas a woven carpet; if you pull on a loose thread it might only affect the thread and those closest to it or... it mightunravel the whole carpet.
One important role of biodiversity (or variety) is that it helps keep the nutrients, such as nitrogen, in the soil. Forexample, a diversity of organisms in the soil allows nutrient recycling to happen. Biodiversity also allows plantsto be pollinated by different types of insects. And of course, different species of fungi are necessary to recyclewastes from dead plants and animals. These are just a few of the many examples of how biodiversity is importantfor ecosystems.
Vocabulary
• biodiversity: Measurement of the amount of variation of the species in a given area.• extinction: Dying out of a species so that no members of the species exist anymore.
Summary
Video:
Bill Nye the Science Guy- Biodiversity: http://www.youtube.com/watch?v=eSqyoHymN4k
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Practice
Use the resource below to answer the questions that follow.
• In Search of Wild Variety from American Museum of Natural History http://www.youtube.com/watch?v=Pbg_pGZv3CQ (1:52)
1. As of November 2010, about how many species have been identified on the Earth? How close do scientist feelthis number is to the total number of species which exist?
2. In what kinds of locations are new species being found?3. Can different species be identified by just looking at them? What techniques are scientists using to identify
new species?
Review
1. What is biodiversity?2. What does it mean if a place has high biodiversity?3. How does high biodiversity help the stability of an ecosystem?
Additional readings for the chapter:
"Environmental Fact Sheets" (produced by the Young People’s Trust for the Environment):
http://www.ypte.org.uk/environmental-facts.php
Missouri Standard(s):
• 4.1.B.c: Predict the possible effects of changes in the number and types of organisms in an ecosystem on thepopulations of other organisms within that ecosystem
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, over-population, water and air pollution, global warming, restoration of natural environments, river bank/coastalstabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain howthese activities affect organisms within an ecosystem
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4.2 Human Causes of Extinction
I can describe harmful human activities and how they affect an ecosystem.
Why are these polar bears threatened?
These polar bears are threatened because of global warming. They depend on the sea ice for their hunting grounds,and this ice is melting away. Plus bears have to make a longer and more hazardous journey to get to the remainingice.
Other Causes of Extinction
In addition to habitat destruction, other human-caused problems are also threatening many species. These includeissues associated with climate change, pollution, and over-population.
Global Warming
Another major cause of extinction is global warming, which is also known as global climate change. During the pastcentury, the Earth’s average temperature has risen by almost 1◦C (about 1.3◦F). You may not think that is significant,
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but to organisms that live in the wild and are constantly adapting to their environments, any climate change can behazardous. Recall that burning fossil fuels releases gasses into the atmosphere that warm the Earth. Our increaseduse of fossil fuels, such as coal and oil, is changing the Earth’s climate. Any long-term change in the climate candestroy the habitat of a species. Even a brief change in climate may be too stressful for an organism to survive. Forexample, if the seas increase in temperature, even briefly, it may be too warm for certain types of fish to reproduce.
Pollution
Pollution adds chemicals, noise, heat, or even light to an environment. This can have many different harmful effectson all kinds of organisms. For example, the pesticide DDT nearly eliminated the peregrine falcon in some parts ofthe world. This pesticide caused falcons to lay eggs with thinner shells. As a result, fewer falcon eggs survived tohatching. Populations of peregrine falcons declined rapidly. DDT was then banned in the U.S. and peregrine falconpopulations have recovered.
Water pollution threatens vital freshwater and marine resources throughout the world ( Figure 4.2). Specifically,industrial and agricultural chemicals, waste, and acid rain threaten water. As water is essential for all ecosystems,water pollution can result in the extinction of species.
FIGURE 4.2A bird that was the victim of an oil spill. About 58,000 gallons ofoil spilled from a South Korea-bound container ship when it struck atower supporting the San Francisco-Oakland Bay Bridge in dense fog inNovember, 2007.
Finally, soil contamination can also result in extinction. Soil contamination can come from toxic industrial (factory)and municipal (in town) wastes , salts from irrigation, and pesticides from agriculture. These all degrade the soil aswell. As soil is the foundation of terrestrial ecosystems, this can result in extinction.
FIGURE 4.3Soil contamination caused by chemicalproducts and waste.
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Human Overpopulation
Human populations are on the rise. The human population passed the 7 billion mark in October of 2011, and willpass 8 and 9 billion probably before the middle of the century. All these people will need resources such as places tolive, food to eat, and water to drink, and they will use energy and create waste. Essentially, human population growthcan effect all other causes of extinction. For example, more people on the Earth means more people contributingto global warming and pollution. More people also means more clearing of land for agriculture and development.Recall that development by humans often causes habitats to be destroyed. This destruction can force species to goextinct, or move somewhere else.
Vocabulary
• climate: Typical weather in an area over a long period of time.• fossil fuels: Remains of long-dead organisms that now serves as an energy source, such as as oil, coal, or
natural gas.• global warming: Global rise in Earth’s temperature due to increases of greenhouse gasses in the atmosphere.
Summary
Opportunity for Enrichment
Use the resource below to answer the questions that follow.
• Causes of Extinction at http://www.eoearth.org/view/article/150962/
1. What is the primary cause of human-induced extinctions?2. What is considered the greatest contributor to the extinction of many species?3. What was the effect effect of the introduction of mammalian predators to New Zealand?
Review
1. Define global warming. Why is global warming an issue to organisms?2. How could the high human population growth rate drive further extinctions of plants and animals?3. Give an example of how pollution can threaten organisms.
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Missouri Standard(s):
• 4.1.B.c: Predict the possible effects of changes in the number and types of organisms in an ecosystem on thepopulations of other organisms within that ecosystem
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, over-population, water and air pollution, global warming, restoration of natural environments, river bank/coastalstabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain howthese activities affect organisms within an ecosystem
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4.3 Outdoor Air Pollution
I can describe harmful human activities and how they affect an ecosystem.
What is this haze?
The tallest towers of Shanghai, China, rise above the haze. Shanghai’s smog is a mixture of pollution from coal, theprimary source of energy for most homes and businesses in the region, as well as emissions from vehicles. Smog isair pollution that reduces visibility. The term "smog" was first used in the early 1900s to describe a mix of smokeand fog.
Outdoor Air Pollution
Air is all around us. Air is essential for life. Sometimes, humans can pollute the air. For example, releasing smokeand dust from factories and cars can cause air pollution. Air pollution is due to chemical substances and particlesreleased into the air mainly by human actions. This pollution affects entire ecosystems around the world. Pollutioncan also cause many human health problems, and it can also cause death. Air pollution can be found both outdoorsand indoors.
Outdoor air pollution is made of chemical particles. When smoke or other pollutants enter the air, the particles foundin the pollution mix with the air. Air is polluted when it contains many large toxic particles. Outdoor air pollution
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changes the natural characteristics of the atmosphere. Primary pollutants are added directly to the atmosphere. Firesadd primary pollutants to the air. Particles released from the fire directly enter the air and cause pollution ( Figure4.4). Burning of fossil fuels such as oil and coal is a major source of primary pollutants ( Figure 4.5).
FIGURE 4.4Wildfires, either natural or human-caused,release particles into the air, one of themany causes of air pollution.
FIGURE 4.5A major source of air pollution is the burn-ing of fossil fuels from factories, powerplants, and motor vehicles.
Secondary pollutants are formed when primary pollutants interact with sunlight, air, or each other. They do notdirectly cause pollution. However, when they interact with other parts of the air, they do cause pollution. Forexample, ozone is created when some pollutants interact with sunlight. High levels of ozone in the atmosphere cancause problems for humans.
Sources of Outdoor Air Pollution
Most air pollutants can be traced to the burning of fossil fuels. Fossil fuels are burned during many processes,including in power plants to create electricity, in factories to make machinery run, in power stoves and furnaces forheating, and in waste facilities. Perhaps one of the biggest uses of fossil fuels is in transportation. Fossil fuels areused in cars, trains, and planes.
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Air pollution can also be caused by agriculture, such as cattle ranching and the use of fertilizers and pesticides. Othersources of air pollution include the production of plastics, refrigerants, and aerosols, in nuclear power and defense,from landfills and mining, and from biological warfare.
Acid Rain
One result of air pollution is acid rain. Acid rain forms when air pollution combines with precipitation. Sulfuroxides and nitrogen oxides in the air both cause acid rain to form. Sulfur oxides are chemicals that are releasedfrom coal-fired power plants, factories or in our own homes. Nitrogen oxides are released from motor vehicleexhaust. Most of these acid gases are blown into the sky, and when they mix with the clouds it can cause rain -or snow, sleet, fog, mist or hail - to become more acidic. This rain can be very destructive to wildlife. When acidrain falls in forests, freshwater habitats, or soils, it can kill insects and aquatic life. The acid takes away importantminerals from the leaves and the soil.
FIGURE 4.6A forest in the Jizera Mountains of theCzech Republic shows effects caused byacid rain. What do you observe?
Global Warming
Pollutants also affect the atmosphere through their contribution to global warming. Global warming is an increase inthe Earth’s temperature. It is thought to be caused mostly by the increase of greenhouse gases like carbon dioxide.Greenhouse gases can be released by factories that burn fossil fuels. Over the past 20 years, burning fossil fuelshas produced about three-quarters of the carbon dioxide from human activity. The rest of the carbon dioxide in theatmosphere is there because of deforestation, or cutting down trees. Trees absorb carbon dioxide during cellularrespiration, so when trees are cut down, they cannot remove carbon dioxide from the air.
This increase in global temperature will cause the sea level to rise. It is also expected to produce an increase inextreme weather events and change the amount of precipitation. Global warming may also cause food shortages andspecies extinction
Vocabulary
• acid rain: Low-pH precipitation that forms when air pollution combines with water.
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• air pollution: Pollution caused by chemical substances and particles released into the air mainly by humanactions, such as the burning of fossil fuels.
Summary
Practice
Use the resource below to answer the questions that follow.
• Human Pollution at http://www.youtube.com/watch?v=HRJ6njStTec (2:15)
1. What are pollutants?2. What are three sources of pollutants?3. What are the two main categories of pollutants?
Review
1. What is air pollution?2. What’s the difference between primary and secondary pollutants? Give examples of each.3. What are three ways that polluting fossil fuels are burned?4. Why is acid rain dangerous?
Missouri Standard(s):
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, over-population, water and air pollution, global warming, restoration of natural environments, river bank/coastalstabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain howthese activities affect organisms within an ecosystem
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4.4 Sources of Water Pollution
I can describe harmful human activities and how they affect an ecosystem.
Is the ocean a good dumping ground?
Unfortunately some people think so. A lot of garbage ends up washing ashore, and some garbage stays floating outin the ocean. Animals can be strangled by floating trash or mistake inedible trash for food. Not only is the pollutionof our oceans a problem, but also our precious freshwater resources are often polluted.
Sources of Water Pollution
While to many people clean water may seem limitless and everywhere, to many others this is not so. Water pollutionis a serious issue facing hundreds of millions of people world-wide, having harmful effects on the lives of thosepeople. Water is not in unlimited supply and cannot just be made fresh when it is wanted. Water is actually a limitedresource, and for many people, fresh, unpolluted water is hard to find. A limited resource is one that we use fasterthan we can remake it. It is a resource that can be used up.
Water pollution happens when contaminants enter water bodies. Contaminants are any substances that harm thehealth of the environment or humans. Most contaminants enter the water because of humans. Surface water (riveror lake) can be exposed to and contaminated by acid rain, storm water runoff, pesticide runoff, and industrial waste.This water is cleaned somewhat by exposure to sunlight, aeration, and microorganisms in the water. Groundwater
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(private wells and some public water supplies) generally takes longer to become contaminated, but the natural clean-ing process also may take much longer. Groundwater can be contaminated by disease-producing pathogens, carelessdisposal of hazardous household chemical-containing products, agricultural chemicals, and leaking undergroundstorage tanks.
FIGURE 4.7Water pollution can cause harmful effects to ecology and human health.Shown is the pollution in Jakarta, Indonesia.
Natural events, like storms, volcanic eruptions and earthquakes can cause major changes in water quality. Buthuman-caused contaminants have a much greater impact on the quality of the water supply. Water is consideredpolluted either when it does not support a human use, like clean drinking water, or a use for other animals andplants. The overgrowth of algae, known as an algal bloom, can result from the runoff of fertilizer into bodies ofwater. This excess of nutrients allows the algae to grow beyond control, bring harm to the rest of the ecosystem.
The main sources of water pollution can be grouped into two categories:
• Point source pollution results from the contaminants that enter a waterway or water body through a singlesite. Examples of this include untreated sewage, wastewater from a sewage treatment plant, and leakingunderground tanks.
• Nonpoint source pollution is contamination that does not come from a single point source. Instead, it happenswhen there is a buildup of small amounts of contaminants that collect from a large area. Examples of thisinclude fertilizer runoff from many farms flowing into groundwater or streams.
Do we have an infinite supply of drinkable water?
No. In fact, in many parts of the world, finding clean drinkable water is difficult. This can lead to various serioushealth issues. Hundreds of millions of people world-wide are thought to live in areas where obtaining safe water isdifficult. This makes preserving water resources an important global issue.
Preserving Water Sources
It might seem like there is plenty of water on Earth, but that’s not really the case. Water is a limited resource . Thatmeans that it is used faster than it is replaced. Theoretically, at some point in time, the supply of fresh water couldrun out. Though this is unlikely, it is possible. But it is a significant issue in parts of the world with large populations.As these populations continue to grow, the supply of water becomes an increasingly important issue.
Even though we have lots of water in our oceans, we cannot use that water whenever we want. It takes specialequipment, such as a desalination plant, and a lot of energy (and money) to convert salt water into fresh water. Of
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all the water on Earth, only about 1% can be used for drinking water. Almost all of the rest of the water is either saltwater in the ocean or ice in glaciers and ice caps. As a result, there are water shortages many places in the world.Since we have such a limited supply of water, it is important to preserve our water supplies. Therefore, steps havebeen taken to prevent water pollution. Technologies have also been developed to conserve water and prevent waterpollution.
Sub-Saharan African countries have the most vulnerable water supplies. Some scientists believe of a potential futurecrisis in both Asia and Africa from pollution and depletion of natural water resources. Many countries in the MiddleEast are at an extreme risk of water shortages. Diminished water supplies could increase the risk of both internalconflicts or wars between countries.
Preventing
In the U.S., concern over water pollution has resulted in many federal laws. Some of these laws go all the way backto the 1800s! The laws prohibit the disposal of any waste into the nation’s rivers, lakes, streams, and other bodies ofwater, unless a person first has a permit. Growing concern for controlling water pollutants led to the enactment ofthe Clean Water Act in 1972. The Clean Water Act set water quality standards. It also limits the pollution that canenter the waterways. Other countries are also actively preventing water pollution and purifying water.
Wastewater Treatment
Fresh water is also preserved by purifying wastewater. Wastewater is water that has been used for washing, flushing,or manufacturing. It includes the water that goes down your shower drain and that is flushed down your toilet.Instead of dumping wastewater directly into rivers, wastewater can be purified at a water treatment plant. Whenwastewater is recycled, waterborne diseases caused by pathogens in sewage can be prevented. What are some waysyou can save water in your own house?
FIGURE 4.8Sewage treatment plant.
Vocabulary
• limited resource: Resource that is used faster than it can be made.• groundwater: Underground water reserves.• water pollution: Pollution due to contaminants entering the water supply.
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Summary
Practice
Use the resource below to answer the questions that follow.
• Water Pollution at http://www.youtube.com/watch?v=ACgv19b-n5E (4:42)
1. How can human sewage throw ecosystems out of balance? What nutrient cycle(s) are involved?2. How does agriculture run-off effect ecosystems? How does this change move through the food web? What
can the result be?3. How can drugs excreted by humans affect aquatic organisms? How does this affect the ecosystem?4. What is heat pollution? What affect can this have on aquatic ecosystems? Explain your answer as fully as
possible.
Review
1. Why is fresh water a limited resource?2. What is water pollution?3. What are two main sources of pollution of surface water?4. What are two main sources of groundwater pollution?5. What’s the difference between a point source and nonpoint source of water pollution?
Missouri Standard(s):
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, over-population, water and air pollution, global warming, restoration of natural environments, river bank/coastalstabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain howthese activities affect organisms within an ecosystem
• 4.1.D.b: Predict the impact (beneficial or harmful) of a natural environmental change (e.g., forest fire, flood,volcanic eruption, avalanche) on the organisms in an ecosystem
• 5.3.A.b: Describe the effect of human activities (e.g., landfills, use of fertilizers and herbicides, farming,septic systems) on the quality of water
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4.5 Habitat Destruction
I can describe harmful human activities and how they affect an ecosystem.
What’s happening to this land?
This picture, taken in southern Mexico, shows land being cleared for agriculture. The forest has been cut down andburned to make room for a a farm. In the process, homes to many plants and animals were destroyed. This is anexample of habitat destruction.
Habitat Destruction
From a human point of view, a habitat is where you live, go to school, and go to have fun. Your habitat can bealtered, and you can easily adapt. Most people live in a few different places and go to a number of different schoolsthroughout their life. But a plant or animal may not be able to adapt to a changed habitat. A habitat is the naturalhome or environment of an organism.
Habitat destruction is the process by which natural habitat is damaged or destroyed to such an extent that it nolonger is capable of supporting the species and ecological communities that naturally occur there. Natural homes,or habitats, can be destroyed directly by many human activities, most of which involve the clearing of land for
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other uses such as agriculture, mining, logging, hydroelectric dams and urbanization. Habitat can also be destroyedindirectly by human activities such as pollution, fragmentation, climate change and the introduction of invasivespecies. Although much habitat destruction can be attributed to human activity, it is not an exclusively man-madephemomenon. Habitat loss also occurs as a result of natural events such as floods, volcanic eruptions, earthquakes,and climate fluctuations. What changes to the ecosystem do you predict these natural events can cause?
Although habitat destruction primarily causes species extinctions, it can also open up new habitat that might providean environment in which new species can evolve, thus demonstrating the resiliency of life on Earth. Sadly, humansare destroying natural habitats at a rate and on spatial scales that exceed what most species and communities cancope with.
Fast-growing human population fuels habitat destruction. As population increases, humans use more land foragriculture and cities and towns spread out ever-widening areas. Within the past 100 years, the amount of totalland used for agriculture has almost doubled. Land used for grazing cattle has more than doubled. Agriculturealone has cost the United States half of its wetlands and almost all of its tall grass prairies (Figure 4.10). Nativeprairie ecosystems, with their thick fertile soils, deep-rooted grasses, diversity of colorful flowers, burrowing prairiedogs, and herds of bison and other animals, have virtually disappeared. The effects of habitat destruction not onlyimpact native species and animals, but they impact human populations as well. Degraded lands are frequently lostto erosion, desertification, and nutrient depletion. Natural disasters such as floods, droughts, outbreak of pests andwater pollution take a toll on human populations (Figure 4.9).
Conservationists often seek to protect habitat in order to save species. For example, the Biodiversity Hotspot programorganized by Conservation International protects fragile habitats around the world. Their aim is to protect areasaround the globe that contain high concentrations of threatened species. Habitat destruction is not the only threatfacing wildlife, but it is quite likely the greatest threat. If the depletion of natural habitat around the globe does notslow, mass extinctions are sure to follow and, as a result, the loss of biodiversity.
FIGURE 4.9Wetlands such as this one in CapeMay, New Jersey, filter water and protectcoastal lands from storms and floods.
Slash-and-Burn Agriculture
Other habitats that are being rapidly destroyed are forests, especially tropical rainforests. The largest cause ofdeforestation today is slash-and-burn agriculture (shown in the opening image). This means that when people wantto turn a forest into a farm, they cut down all of the trees and then burn the remainder of the forest. This techniqueis used by over 200 million people in tropical forests throughout the world.
As a consequence of slash-and-burn agriculture, nutrients are quickly lost from the soil. This often results in people
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FIGURE 4.10The Flint Hills contain some of the largestremnants of tallgrass prairie habitat re-maining in North America.
abandoning the land within a few years. Then the top soil erodes and desertification can follow. Desertification turnsforest into a desert, where it is difficult for plants to grow. Half of the Earth’s mature tropical forests are gone. Atcurrent rates of deforestation, all tropical forests will be gone by the year 2090.
Invasive/Non-native Species
One of the main causes of extinction is introduction of exotic species into an environment. These exotic and newspecies can also be called invasive species or non-native species. An invasive species can be any kind of livingorganism—an amphibian, plant, insect, fish, fungus, bacteria, or even an organism’s seeds or eggs—that is notnative to an ecosystem and which causes harm. They can harm the environment, the economy or even, humanhealth. Species that grow and reproduce quickly, and spread aggressively, with potential to cause harm, are giventhe label of “invasive”.
An invasive species does not have to come from another country. For example, lake trout are native to the GreatLakes, but are considered to be an invasive species in Yellowstone Lake in Wyoming because they compete withnative cutthroat trout for habitat.
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How do invasive species spread?
Invasive species are primarily spread by human activities, often unintentionally. People, and the goods we use, travelaround the world very quickly, and they often carry uninvited species with them.
• Ships: Ships can carry aquatic organisms in their ballast water.• Wood products: Insects can get into wood, shipping palettes and crates that are shipped around the world.• Ornamental plants: Some ornamental plants can escape into the wild and become invasive.• Pet trade: Some invasive species are intentionally or accidentally released pets. Burmese pythons are becom-
ing a big problem in the Everglades.
Recently, cargo ships have transported zebra mussels, spiny waterfleas, and ruffe (a freshwater fish) into the GreatLakes. These invasive species are better at hunting for food. They have caused some of the native species to goextinct.
Why do invasive species pose such a threat?
Invasive species cause harm to wildlife in many ways. When a new and aggressive species is introduced into anecosystem, it might not have any natural predators or controls. It can breed and spread quickly, taking over anarea. Native wildlife may not have evolved defenses against the invader or they cannot compete with a species thathas no predators.
The direct threats of invasive species:
• preying on native species• out-competing native species for food or other resources• causing or carrying disease• preventing native species from reproducing or killing their young
The indirect threats of invasive species:
• Changing food webs: Invasive species can change the food web in an ecosystem by destroying or replacingnative food sources. The invasive species may provide little to no food value for wildlife.
• Decreasing biodiversity: Invasive species can alter the abundance or diversity of species that are importanthabitat for native wildlife. Aggressive plant species like kudzu can quickly replace a diverse ecosystem witha monoculture of just kudzu.
• Altering ecosystem conditions: Some invasive species are capable of changing the conditions in an ecosystem,such as changing soil chemistry or the intensity of wildfires.
FIGURE 4.11An exotic species, the brown tree snake, hitchhiked on an aircraft to thePacific Islands, causing the extinctions of many bird and mammal specieswhich had evolved in the absence of predators.
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Examples of Habitat Destruction
A habitat that is quickly being destroyed is the wetland. By the 1980s, over 80% of all wetlands in parts of the U.S.were destroyed. In Europe, many wetland species have gone extinct. For example, many bogs in Scotland have beenlost because of human development.
Another example of species loss due to habitat destruction happened on Madagascar’s central highland plateau.From 1970 to 2000, slash-and-burn agriculture destroyed about 10% of the country’s total native plants. The areaturned into a wasteland. Soil from erosion entered the waterways. Much of the river ecosystems of several largerivers were also destroyed. Several fish species are almost extinct. Also, some coral reef formations in the IndianOcean are completely lost.
Additional reading sources:
"Impact of habitat loss on species": http://wwf.panda.org/about_our_earth/species/problems/habitat_loss_degradation/
(Check out the additional links on the left hand side and the tabs at the bottom of the page).
"Marine Habitat Destruction": http://ocean.nationalgeographic.com/ocean/critical-issues-marine-habitat-destruction/
"Habitat Loss: Causes and Consequences": http://www.learner.org/courses/envsci/unit/text.php?unit=9&secNum=7
(HIgher level reading that would be good as an enrichment article).
Vocabulary
• extinction: Complete disappearance of a species.• habitat: Natural home or environment of an organism; the physical environment in which a species lives.• invasive species: Exotic, introduced species that out-competes the native species.• non-native species: Exotic species introduced into a new habitat.
Summary
Review
1. What is a habitat?
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2. What are the primary ways that humans destroy habitats?3. Why may invasive species thrive in a new area? Why is this an issue?4. Describe slash-and-burn agriculture.
Missouri Standard(s):
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, over-population, water and air pollution, global warming, restoration of natural environments, river bank/coastalstabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain howthese activities affect organisms within an ecosystem
• 4.1.D.b: Predict the impact (beneficial or harmful) of a natural environmental change (e.g., forest fire, flood,volcanic eruption, avalanche) on the organisms in an ecosystem
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4.6 Reduce, Reuse, and Recycle
I can understand the importance of reducing, reusing and recycling to help conserve resources.
How can you help conserve our natural resources?
Reduce, reuse, and recycle. There are steps that you personally can take to conserve our natural resources and reducewaste. The waste that an individual creates is small in proportion to all the waste produced by society. Yet all smallcontributions, when added up, make a difference.
Reduce, Reuse, and Recycle
Why conserve resources? During your lifetime, it is possible that the world may run out of some nonrenewableresources, especially as the population passes 8 then 9 billion people. So it is necessary to try to make theseresources last as long as possible. You may have heard people say, "Reduce, Reuse, Recycle." You may know thatthis is the slogan of the campaign to conserve resources. But what do each one of those words truly mean?
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Reduce
What exactly does it mean to reduce? Reducing means decreasing the amount of waste we create. That could alsomean cutting down on use of natural resources. Minimizing of waste may be difficult to achieve for individualsand households, but here are some starting points that you can include in your daily routine to reduce the use ofresources:
• Turn lights off when not using them.• Turn the television off when no one is watching.• Replace burned out bulbs with ones that are more energy-efficient ( Figure 4.12).• Reduce water use by turning off faucets when not using water.• Use low-flow shower heads, which save on water and use less energy.• Use low-flush and composting toilets.• Put kitchen and garden waste into a compost pile.• In the summer, change filters on your air conditioner and use as little air conditioning as possible. The use of
air conditioning uses a lot of energy.• In winter, make sure your furnace is working properly and make sure there is enough insulation on windows
and doors.• Mend broken or worn items instead of buying new ones.• When you go shopping for items, buy quantities you know you will use without waste.• Walk or bicycle instead of using an automobile, in order to save on fuel usage and costs, and to cut down on
pollution.• When buying a new vehicle, check into hybrid, semi-hybrid, or electric models to cut down on gas usage and
air pollution.
FIGURE 4.12These fluorescent light bulbs are muchmore energy efficient than standard lightbulbs.
Reuse
Let’s now look at what we can reuse. Reusing includes using the same item again for the same function and alsousing an item again for a new function. Reuse can have both economic and environmental benefits. New packagingregulations are helping society to move towards these goals. Some ways of reusing resources include:
• Use reusable bags when shopping.
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• Use gray water. Water that has been used for laundry, for example, can be used to water the garden or flushtoilets.
• At the town level, purified sewage water can be used for fountains, watering public parks or golf courses, firefighting, and irrigating crops.
• Rain can be caught in rain barrels and used to water your garden.
What are some other ways to reuse resources?
Recycle
Now we move on to recycle . Sometimes it may be difficult to understand the differences between reusing andrecycling. Recycling involves processing used materials in order to make them suitable for other uses. That usuallymeans taking a used item, breaking it down, and reusing the pieces. Even though recycling requires extra energy, itdoes often make use of items which are broken, worn out, or cannot be reused.
The things that are commonly recycled include:
• Batteries.• Biodegradable waste.• Electronics.• Iron and steel.• Aluminum ( Figure 4.13).• Glass.• Paper.• Plastic.• Textiles, such as clothing.• Timber.• Tires.
FIGURE 4.13These aluminum cans are packed to-gether in a recycling plant to be reused.
Each type of recyclable requires a different recycling technique. Here are some things you can do to recycle in yourhome, school, or community:
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• If you have recycling in your community, make sure you separate aluminum, plastics, glass, and paperproducts.
• See if your school recycles. If not, you and some friends could start a recycling club, or organize efforts tobetter recycling goals.
Laws can also be created to make sure people and companies reduce, reuse, and recycle. Individuals can vote forleaders who stand for sustainable ecological practices. They can also tell their leaders to make wise use of naturalresources. You can also influence companies. If you and your family only buy from companies and restaurantsthat support recycling or eco-friendly packaging, then other companies will also change to be more environmentallyfriendly.
Vocabulary
• natural resource: Something supplied by nature that helps support life.• nonrenewable resource: Natural resource that is used up faster than it can be made by nature.
Summary
Review
1. What are four examples of recyclable materials?2. What are two ways you can reduce the amount of waste you create?3. What are two ways of reusing materials?
Missouri Standard(s):
• 4.1.D.a: Describe beneficial and harmful activities of organisms, including humans (e.g., deforestation, over-population, water and air pollution, global warming, restoration of natural environments, river bank/coastalstabilization, recycling, channelization, reintroduction of species, depletion of resources), and explain howthese activities affect organisms within an ecosystem
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4.7 References
1. USFWS Pacific. Coral reefs are one of the biomes with the highest biodiversity on Earth.2. Ingrid Taylar. This bird was the victim of an oil spill.3. Image copyright Mikadun, 2013. Soil contamination can cause extinction in terrestrial ecosystems.4. Bureau of Land Management (Flickr:BLMOregon). Wildfires generate particles that contribute to air pollu-
tion.5. Courtesy of the National Parks Service. A major source of air pollution is the burning of fossil fuels in
factories, power plants, and motor vehicles.6. User:Nipik/Wikimedia Commons. This forest has been severely damaged by acid rain.7. Stephen Codrington. Water pollution causes detrimental effects to both ecology and human health. CC BY
2.58. . Processing wastewater before dumping it into rivers helps conserve fresh water.9. . Processing wastewater before dumping it into rivers helps conserve fresh water.
10. Courtesy of Anthony Bley, U.S. Army Corps of Engineers. Wetlands help to filter water and protect coastallands from storms and floods.
11. USFWS Mountain Prairie. The Flint Hills contain some of the largest remnants of tallgrass prairie habitatremaining in North America.
12. Courtesy of the National Park Service. Exotic species such as the brown tree snake can cause the massextinction of many species.
13. Anton Fomkin. Fluorescent light bulbs are much more efficient than standard incandescent light bulbs..14. Flickr:Mojave Desert. Recycling aluminum cans help saves a large amount of energy.
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