Unit 2 NotesEcologyWhat is Ecology?• Ecology: is the study of the way living things interact with each other and their physical environment. • Oikos: house or place to life,• -logy: the study of. • Biotic Factors: the biological (living) influences on organisms within an ecosystem.• Abiotic Factors: the physical or nonliving factors that shape an ecosystem.• Together, biotic and abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem in which the organism lives.• Resource: any necessity of life, such as water, nutrients, light, food or space.Biological Organization (Hierarchy of Organization):Atoms Molecules Organelles Cells Tissues Organs Organ Systems Organisms Populations (Species) Communities Ecosystems Biomes Biosphere Biological Organization (Hierarchy of Organization):• Species: a group of organisms that can interbreed and produce fertile offspring.• Populations: a group of many individuals of a single species that occupy a common area and share common resources.• Communities: all of the populations (groups of different organisms) that coexist and form systems of production, consumption, and decomposition.• Ecosystems: an isolated self-supporting unit of interacting organisms and their surrounding environment.• Biomes: a group of ecosystems that have all the same climate and dominant communities.• Biosphere: the combined portions of the planet in which all of life exists, including land, water, and air or atmosphere.• Habitat: the surroundings in which a particular species can be found. (“Address”).• Niche: the way of life a species pursues within its habitat. (“Job” = what it does).• Symbiotic Relationships : the living together of two dissimilar organisms (different species) for beneficial reasons. There are 4 general types: 1. Mutualism: both organisms cooperate for mutual benefit. (For example: termites and

protozoans, lichens = fungi and algae, humans and E. coli). 2. Commensialism: one organism (species) is helped and the other is not helped nor harmed.

For example: birds and trees, orchids and trees – epiphytes, Burrowing animals using another’s previous den.

3. Parasitism: one organism benefits and the other is harmed to some extent, maybe even killed. (For example: mistletoe on cedar trees, kudzu, colds/viruses*).

4. Ammensalism the interaction in which one species is hurt, but the other does not benefit. For example, streamside vegetation frequently is trampled by animals coming to drink.

Autotrophs• Autotrophs: organisms that use energy from the sun or energy stored in chemical compounds to manufacture their own nutrients. Also called producers.• Photosynthesis: the process by which plants and some other organisms use light energy to power chemical reactions that convert water and carbon dioxide into oxygen and high-energy carbohydrates such as sugars and starches.• Chemosynthesis: the process by which some organisms use chemical energy to produce carbohydrates. Heterotrophs• Heterotrophs: organisms that cannot make their own food and must feed on other organisms for energy and nutrients. Also called consumers.• Energy flows through an ecosystem in one direction, from the sun or inorganic compounds to autotrophs (producers) and then to heterotrophs (consumers).The most obvious ways that organisms interact in communities/ecosystems is by feeding patterns. • Herbivores: a consumer that eats producers. Producers will develop mechanisms of defense.• Carnivores: a consumer that eats other consumers. Prey will adapt in order to survive.• Omnivores: a consumer that eats both producers and consumers.• Detritivores: organisms that feed on plant and animal remains and other dead matter collectively known as detritus. (Sometimes known as scavengers).• Saprophytes: (Also known as Decomposers) organism like fungi and bacteria that break down dead organisms and return the nutrients to the soil.• Food Chains: usually there are 4 or 5 trophic or feeding levels.• Food Webs: a network of intertwined food chains with several different trophic levels.• Trophic Level: organism in a food chain that represents a feeding step in the passage of energy and materials through an ecosystem.• Ecological Pyramids : diagrams (sideways bar graphs) that aid in visualizing increase and decreases.• The energy pyramid shows the available amount of energy at trophic level. Only about 10% of the energy available within one trophic level is transferred to organisms at the next trophic level.• The biomass pyramid shows the total amount of living tissue within a given trophic level, usually expressed in terms of grams of organic matter per unit area.• The pyramid of numbers provides a detailed view of number of individual organisms in an ecosystem. • The first level consists of the producers (usually plants). All higher levels are consumers. • Sometimes the pyramids get reversed in the pyramid of numbers. This happens when there are fewer (usually large) producers than consumers. In these instances the pyramid is upside down.

• The shorter the food chain the more energy is available to organisms. Therefore, most natural ecosystems do not have more than five levels to their pyramid of numbers. Large carnivores are rare because there is so little energy available to them atop the pyramid. Remember – only 10% goes on to the next trophic level.• Unlike the one way flow of energy, matter is recycled within and between ecosystems through biogeochemical cycles:• Organisms all need material resources (usually inorganic compounds) and ecosystems have patterns of material flow between species and trophic levels.• Often the flow is cyclic, so that materials spend lots of time in the system and do not simply flow in one side and out of the other.• Hydrologic Cycle: the water cycle (evaporation and transpiration, condensation, precipitation). • Oxygen/ Carbon Cycle: the movement of oxygen and carbon through the processes of photosynthesis and respiration. • Nitrogen Cycle: important bacteria (nitrogen fixation and denitrification) in soil convert nitrogen into forms that are usable by all organisms. • Phosphorus Cycle: the movement of phosphates, usually absorbed by plants and then moved throughout the food web. • Primary Productivity: the rate at which organic matter is created by producers in an ecosystem. This is often controlled by the rate of available nutrients. • Limiting Nutrients: a single nutrient, that is scarce or cycles very slowly, that limits primary productivity.• Weather: the day-to-day condition of the Earth’s atmosphere at a particular time and place.• Climate: the average, year-after-year conditions of temperature and precipitation that influence life in a particular region.• Partially results from the curvature of the Earth and the density of solar insulation.• The curve spreads density of solar radiation over greater surface area at poles than equator.• Sunlight has to travel through more atmosphere at poles than equator due to decreased angle.• Poles are colder because of this, but this is not the reason for…• Seasonality in temperature is a result of the tilt of Earth's axis.• The tilt is 23.5° which enables us to divide the earth into latitudinal regions

– Arctic and Antarctic Circles • Dividing line between those regions that get 24 hr of sunlight at height of summer, 24 hr of darkness in depths of winter and those regions that get some dark and light periods every day – Equator • Circumference midway between N. and S. poles – Tropics • Regions of earth where the sun is directly overhead at least once a year • Go from 23.5° N (Tropic of Cancer) to 23.5° S (Tropic of Capricorn)

• The tilt divides up the year as well as the Earth.– Solstices (Winter and Summer) • Shortest and longest days of the year.– Equinoxes (Autumnal and Vernal) • Days on which there are 12 hrs of sunlight and 12 hrs of darkness.

• Ecosystems are constantly changing in response to natural and human disturbances. As an ecosystem changes, older inhabitants gradually die out and new organisms move in, causing further changes in the community. Communities replace, or succeed, each other in a predictable, orderly way known as ecological succession. Succession may take hundreds to thousands of years. • There are two types of ecological succession: Primary and Secondary succession.

1. Primary Succession: the development of communities in areas that have not supported communities before (for example: bare rock, lava flows, new lakes formed by glaciers etc...).

• There are several steps in primary succession.• 1st Stage (the Pioneer Stage or Sere): hardy organisms (pioneer species) that can survive under adverse conditions.• 2nd + Stage/Sere: organisms that can cause minor changes (for example: plants casting a shadow which cools the area, animals causing changes in the food web).

2. Secondary Succession: the faster development of communities in areas that have supported communities before. For example: a forest being cleared to grow crops, the abandonment of the “farm,” then the forest grows back again.

• There are two types of secondary succession:A. Allogenic succession (literally, "other origin“) is caused by an abiotic disturbance such as

humans or a natural disaster.B. Autogenic succession (literally, "self origin") is caused by a disturbance due to organisms

within the system – A locust plague can cause a disturbance large enough to initiate succession once the grasshopper populations have returned to low levels – An outbreak herbivores (gypsy moth in oak forests, spruce budworm in spruce forests, pine beetles in forests around here) can lead to widespread loss of the climax tree species and initiate succession

• Seral Community: an intermediate community that replaces another (a transition community).• Climax Community: a stable community that will change little unless altered by a human or natural disaster.• Climax communities can be grouped into major Biomes or climate regions.• Microclimate: the climate within a small area that differs significantly from the climate around it. Marine Ecosystems:

• Photic Zone: the top zone of the ocean where sunlight can penetrate and photosynthetic producers like algae can be found.• Aphotic Zone: a permanently dark zone below the photic zone where light cannot penetrate. Any producers in this zone are chemosynthetic autotrophs.• Intertidal Zone: the area along coast lines that is exposed during low tides, but covered with water during high tides. • One of the most interesting is known as the rocky intertidal. Here organisms are adapted to holding on or attaching themselves to the rocks. • Competition in this zone often leads to zonation, which is the prominent horizontal banding of organisms in their respective niches within this habitat.• Coastal Ocean: the area extending from the low-tide line to the edge of the continental shelf which is usually within the photic zone. Therefore, this zone has lots of plankton and other organisms. • One example of a coastal ocean community is the kelp forests. These giant brown algae support an incredibly complex food web.• Coral Reef: areas in warm shallow waters that produce structures made from the calcium carbonate skeletons of coral animals. • Many of these coral animals live symbiotically with photosynthetic algae and provide for an incredible array of organisms.• Open Ocean: the area from the edge of the continental shelf outward. • The top part of this region is part of the photic zone, where plankton lives. This zone is dominated by fish and marine mammals.• Benthic Zone: the ocean floor of the coastal ocean and the open ocean. • Organisms in this zone are called benthos because they live on the oceans bottom. Most of these organisms depend on food, organic material (detritus) drifting down or chemosynthetic organisms.• Estuaries: wetlands formed where rivers meet the ocean. • They contain a mixture of fresh and salt water and are affected by tides. • Estuaries support an incredible amount of life as they serve as spawning and nursery areas for many animals. • They are unusual in that their primary production is not consumed as much by herbivores. Instead much of it enters the food web as tiny organic materials known as detritus.• Salt Marshes: temperate-zone estuaries dominated by salt-tolerant grasses (such as Spartina) above the low-tide line and sea grasses underwater.• Mangrove Swamps: coastal wetlands that are widespread across tropical regions. Like salt marshes, they have sea grasses underwater, but have salt-tolerant trees like mangroves above the low-tide line.Freshwater Ecosystems:• Flowing-Water (Lotic) Ecosystems:• Rivers, streams, creeks and brooks.• Organisms living here are adapted to the rate of flow.• Often turbulent and oxygen rich near their source, but slowing and building up sediments further from the source.• Standing-Water (Lentic) Ecosystems:

• Lakes and ponds.• Water will flow in and out, but water also circulates within the system too.• Provide habitats for many organisms that would quickly be washed away in a flowing-water ecosystem. Plankton: tiny, free-floating or weakly swimming organisms including phytoplankton (photosynthetic plankton) and zooplankton (heterotrophic plankton that often feeds on phytoplankton).

• Freshwater Wetlands:• Wetlands are an ecosystem in which water either covers the soil or is present at or near the surface of the soil for at least part of the year.• Many are very productive ecosystems.• Three types: Bogs, Marshes and Swamps.– Bogs: typically formed in depressions left by the glaciers. Sphagnum moss grows here and the water tends to be acidic.– Marshes: shallow wetlands along rivers with tall grass-like plants.– Swamps: “flooded forests,” distinguished from marshes by the presence of trees and shrubs. • Terrestrial Ecosystems: each is defined by a unique set of abiotic factors and has a characteristic ecological community.Tundra:Abiotic Factors:• Location: Northern North America, Asia and Europe.• Temperatures: very cold, averages -11 oC. Ranges between -30 oC in the winter to +10 oC in the summer. Has permanently frozen ground to about one meter below the surface (deep) known as permafrost, which only thaws a few centimeters in the summer.• Precipitation: low, 15 to 20 centimeters annually. Almost all in the form of snow. Can be considered a frozen “desert.” However, they have “soggy” summers as the snow and ice thaw.• Soil: poorly developed along with permafrost.Biotic Factors:• Flora: must be adapted for extremely cold temperatures: ground-hugging plants such as mosses, lichens, sedges and short grasses. Some shrubs and small trees.• Fauna: like flora, must be adapted for the extremely cold temperatures. Migratory birds, mammals with fur coats such as caribou, polar bears, wolves, fox, hares, and lemmings.Taiga or Boreal Forest:Abiotic Factors:• Location: North America, Asia and Northern Europe.

• Temperatures: long cold harsh winters, short mild/warm summers (only a few months long).• Precipitation: moderate precipitation, usually in the form of snow (= 20 to 60 centimeters of rain) and high humidity.• Soil: acidic and nutrient-poor soilBiotic Factors:• Flora: Conifers such as spruce, pines, fir, hemlock, along with hardy deciduous trees including oak, maples, birch, and aspen. Most of the trees are extremely slow in growing (takes about 7 years to grow one foot.) and tend to be shorter versions of trees found in other climate regions.• Fauna: seed-eaters (birds and small mammals), insects, deer, moose, elk, hares, bears, wolves, beavers, lynx, wolverines, (mammals with heavy winter coats).

Northwest Coniferous Forest or Temperate Rain Forest:Abiotic Factors:• Location: Pacific coast of Northwestern U.S. and Canada, from Northern California to Alaska. • Temperatures: mild temperatures due to the moderating effects of the ocean. Often cool in the summer.• Precipitation: abundant during fall, winter and spring. Drier in the summer.• Soils: rocky and acidic soils.Biotic Factors:• Flora: made up of a variety of conifers, including fir, spruce, hemlock and redwoods.• Fauna: bears, large herbivorous and smaller mammals, insects, and birds. Very few, amphibians and reptiles.Deserts:Abiotic Factors:• Location: Northern Africa, Mid to Southern Asia, The Middle East, Western U.S., Mexico, Western South America, Western and Southern Australia.• Temperatures: wide daily variation. “Summer” temperatures can reach 43 oC during midday and then drop to 13.5 oC at night.• Precipitation: characterized by a lack of precipitation (less than 25 centimeters per year).• Soils: rich in minerals but poor in organic material.Biotic Factors:• Flora: the dominant vegetation consists of widely scattered shrubs, cacti, and succulents (often called xerophytes). Plants have adaptations for water conservation:– Long roots to tap water deep in the ground.– Shallow but extensive (widely spread) root system.– Water storage systems (for example: the cacti).– Thick outer coverings, or protective devices (thorns).

– Needle-like leaves or leaves that curl.– Produce numerous seeds for times when water is available.• Fauna: seed-eating animals: insects, rodents, and birds. Predators of the seed-eating animals: reptiles, birds of prey, a few mammals. The animal also have adaptations to help them survive:– Storage of water.– Burrow or seek shelter.– Anatomical and physiological adaptations: (for example: large ears of rabbits to get rid of heat. Camels being capable of going without water for extended periods of time).

Temperate Grasslands:Abiotic Factors:• Location: Central Asia, North America, Australia, Central Europe, Upland plateaus of South America. Some of the areas have other common names: Prairie (North America), Steppe (Asia), Pampas (South America).• Temperatures: moderate seasonal variation, ranging from very cold (-30 oC) in the winter to warm/hot (+30 oC) in the summer.• Precipitation: moderate and seasonal, about 75 centimeters annually, occasional droughts and fires.• Soil: fertile soils.Biotic Factors:• Flora: grasses/food crops, vegetation that can survive droughts or fires, dormant in the winter, and that is resilient to grazing.• Fauna: various mammals (including large grazing mammals), birds, insects, reptiles, and some amphibians.Tropical Savanna:Abiotic Factors:• Location: Eastern Africa, Southern Brazil, and Northern Australia.• Temperatures: warm temperatures.• Precipitation: seasonal with frequent droughts and fires.• Soil: compact and dry soils.Biotic Factors:• Flora: grasses, vegetation that can survive droughts or fires, dormant, that is resilient to grazing. Some trees and shrubs.• Fauna: various mammals (including large grazing mammals), birds, insects, reptiles, and some amphibians.

(Temperate) Deciduous Forests:Abiotic Factors:• Location: Eastern U.S., South Eastern Canada, Europe, Japan, China, Australia• Temperatures: moderate seasonal variation, ranging from very cold (-30 oC) in the winter to warm/hot (+30 oC) in the summer.• Precipitation: generally high (60 to 100 centimeters annually) and fairly evenly distributed throughout the year.• Soils: fertile, often rich in humus (a material formed from decaying leaves and other organic matter).Biotic Factors:• Flora: a 5 to 6 month growing season. Dominated by broadleaf deciduous (trees that drop their leaves and become dormant in the winter) some conifers, flowering shrubs, herbs, and a ground layerof mosses and ferns. • Fauna: various animal life is found here. Small to medium sized mammals (deer, black bears, squirrels, skunks), birds (song birds and ground birds), “pond dwellers”, and numerous insects. Due to the cold winter temperatures many animals have adapted some survival strategies: migration, hibernation, heavy coats that are molted (shed) in the summer.Temperate Woodland and Shrubland: Abiotic Factors:• Location: Western coasts of North and South America, Mediterranean Sea coastlines, South Africa and South Australia.• Temperatures: Hot summers, cool winters.• Precipitation: semiarid, dry summers, moist winters. Periodic fires.• Soils: nutrient-poor soils.Biotic Factors:• Flora: woody evergreen shrubs; (Chaparral: communities dominated by shrubs). Herbs, grasses and wildflowers.• Fauna: mammals (predatory and herbivores), birds, Insects and some reptiles.Tropical Rain Forest:Abiotic Factors:• Location: South and Central America, Southeast Asia, Southern India, Northeastern Australia.• Temperatures: almost no seasonal variation, the temperatures stay around 25 to 30 oC year round.• Precipitation: extremely high, between 200 to 400 centimeters annually, sometimes more than 500 centimeters.• Soils: thin and very nutrient poor. Nutrients are quickly taken up by vegetation.Biotic Factors:• Flora: enormous variety. Some plants must live on others in order to get sunlight. These are called epiphytes.

• Up to 4 Layers of Vegetation: Ground Layer: “jungle” - very thick, almost impassable vegetation, Understory: short trees, Canopy: tall trees that capture most of the sunlight, and Emergent Trees: occasional trees that rise above the canopy.• Fauna: widest variety of species in the world. Many species are arboreal (live in the trees). Mammals: large cats, monkeys, bats, etc.... Birds, Reptiles, Insects, Amphibians (70% of all amphibian species are found here).Tropical Dry Forest: Abiotic Factors:• Location: parts of Africa, South and Central America, Mexico, India, Australia and tropical islands.• Temperatures: almost no seasonal variation, the temperatures stay around 25 to 30 oC year round.• Precipitation: highly seasonal, alternating wet and dry seasons.• Soils: rich soils subject to erosion.Biotic Factors:• Flora: tall deciduous trees that form a canopy during the wet season and drought tolerant plants.• Fauna: wide variety of species. Mammals: tigers, elephants, rhinoceros, etc.... Birds, Reptiles, Insects, some Amphibians.

Other Land Areas:• Mountain Ranges : Abiotic and biotic factors vary with elevation.Other Land Areas:• Polar Ice Caps : Cold year round, little precipitation (in the form of snow); very little plant life; Marine mammals and some birds make up the dominant wildlife.Population Ecology:• Lag Phase: a period of slow growth, as the population “begins.”• Exponential Growth Phase: a period of rapid growth; the population “double” with each generation.• The Exponential Growth Curve (also known as a J-curve) occurs when there is no limit to population size.• As resources become less available, the growth of a population slows or stops.• Stabilization Phase: a period of population “crashing” as the population levels.• The Logistic Growth Curve (also known as an S-curve) shows the effect of a limiting factor (in this case the carrying capacity of the environment).• Carrying Capacity: the maximum number of individuals of a species that the environment can support. The number of individuals born is equal to the number of individuals that die. Labeled on graphs as k. This is the point/line that the S-curve targets as the stabilization phase.Carrying CapacitySurvivorship/Mortality Curves

• Type I curve • Most mortality comes late.• Often associated with organisms that put a lot of resources in to postnatal care.• Examples: Humans, Trees.Survivorship/Mortality Curves• Type II curve • Mortality is constant throughout life – as likely to die at any time.• Results in a constant proportion of each age class surviving • Examples: many birds are the classic example Survivorship/Mortality Curves• Type III curve • Most mortality comes early.• Often characteristic of organisms that reproduce a great number of offspring once and then die, but there are many exceptions to this generality.• Examples: Salmon, Sea Turtles.• Limiting factors: environmental factors that stabilize population size and keep the species from reaching their biotic potential.• Density-Dependent Limiting Factors: Factors that limit the population density due to the number of individuals that are already there. (For example: space, food, water, predators, parasites, etc...).• Predator-Prey Relationships: the regulation of a population by predation is one of the best known mechanisms of population control. From a graph it can be seen how the populations of the prey and the populations of the predator act on one another and limit the population.

• Here you can see that as the moose population increases (more available food/prey) the wolf population will begin to increase. But as the wolf population increases (more moose are eaten) the moose population will begin to decrease. When the moose population is low (very little food for the wolves) the wolf population will decrease. When the wolf population is low (fewer Predators) the moose population will begin to increase.

• The competitive exclusion principle states that no two species can occupy the same niche in the same habitat at the same time. Anytime, two organisms with the same niche, overlap in the same habitat, competition may result.• Competition: the struggle for limited resources among organisms. There are 2 types of competition.• Intraspecific Competition: when organisms compete with members of their own species. (For example: two guys trying to date the same girl).• Interspecific Competition: when organisms compete with members of other species. (For example: lions and hyenas fighting over an animal’s carcass).

Summary of Interactions in an Ecosystem:• Helped (+)• Hurt (-)• Not Affected (0)

Species A Species BMutualism + +Commensialism + 0Parasitism + -Ammensialism 0 -Herbivory/Carnivory + -Competition - -Predation + -

• Density-Independent Limiting Factors: factors whose effects are not determined by the density of a population. (For example: weather, natural disasters).• Population: a group of organisms of the same species in the same place.• Three important characteristics of a population are its geographic distribution, density and growth rate. • Geographic Distribution: describes the area inhabited by a population. Also called the range.• Population Density: is the number of individuals per unit area. Basically the size of the population.• Three factors can affect population size: the number of births, the number of deaths, and the number of individuals that enter (immigration) or leave (emigration) the population.• Population Dynamics: the study of factors that affect growth, stability, and/or decline of populations. • Population Growth: occurs when available resources exceed the number of individuals able to exploit them. Reproduction is rapid leading to a higher birthrate than the death rate, thus producing a net increase in the population size.• Population Stability: is often proceeded by a "crash" since the growing population eventually outstrips its available resources. Stability is usually the longest phase of a population's life cycle. When reached, the population’s birthrate is approximately that of the population’s death rate and the population size stays relatively the same.• Population Decline: the decrease in the number of individuals in a population due to the death rate and/or emigration rate exceeding the population’s birth rate and/or immigration rate. This can lead to population extinction.• Nearly all populations will tend to grow exponentially, since reproduction is generally a multiplicative process, as long as there are resources available.• Biotic Potential: the rate at which a population would produce young if every individual lived and produced offspring at its maximum capacity.Human Population Growth:

• Like the populations of many other living organisms, the size of the human population tends to increase with time.• During the last 500 years, the human population has experienced an exponential rate of growth. Improvements in agriculture, industry, sanitation, medicine and health care all helped to reduce the death rate. While at the same time the birth rate remained high.

Human Population Ecology• Demography: the study of human populations.• Demographic Transition: a dramatic change in the birth and death rates of some populations where more children survive to adulthood and more adults are living to old age. Initially the population grows rapidly as the death rate starts to fall. The demographic transition is complete when the birthrate falls to meet the death rate, and the population growth stops. This has occurred in the United States, Europe and Japan. However, many other parts of the world are still experiencing exponential growth.• Age Structure Diagrams: A population profile done with a bar graph which shows the number of people in each age group. • Future Population Growth: What will happen to the human population in the future? Based on the patterns that are currently observed, our population will exceed 9 billion by the year 2050. But will our population go that high or higher? Or will the human population peak and either level off or decline?Humans in the Biosphere:• All of the organisms – including humans – that live on Earth share a limited resource base and depend upon the natural ecological processes that sustain these resources.• Humans and their activities impact Earth more than all other species combined.• Biodiversity: a.k.a. Biological Diversity; the sum total of the variety of organisms in the biosphere.• Biodiversity: – Ecosystem Diversity: includes the variety of habitats, communities and ecological processes in the living world.– Species Diversity: Refers to the number of different species in the biosphere.– Genetic Diversity: the sum total of all the different forms of genetic information carried by all organisms living on Earth today. It can also refer to the amount of genetic diversity within each species.• Human activities often reduce biodiversity in the environment.• Extinction: The disappearance of a species from all parts of its geographical range.

• There can be multiple causes for the extinction of a species at the same time. Human activities often times play a role in this.Causes of Extinction• Human alteration of habitat.• Deforestation due – to forestry (“logging”) or – conversion of forest to agricultural field or conversion of grassland to agriculture– or land use for urban expansion. With the addition of machines to the world as a result of the industrial revolution of the 1800s led to the development and growth of cities (urban centers) and soon suburbs. • Agriculture: The practice of farming, or growing your own plants. Very important in human history because it provided people with a dependable supply of food, leading to people gathering and living in larger settlements. The domestication of animals is included in agriculture. • The Green Revolution – the introduction of intensive farming practices (such as monoculture) that lead to a substantial increase in crop yields. Unfortunately agricultural success has also led to more problems.Causes of Extinction• Forest Resources: Forests are sometimes called the “Lungs of the Earth.” They also store nutrients, provide habitats and food for organisms, moderate climate, limit soil erosion and protect water supplies. • About half of the areas originally covered by forests worldwide have been cleared. Old-Growth forests are those that took centuries to form and they are considered nonrenewable. • Deforestation has many severe effects.• Introduction of exotic species can cause extinction of endemic species (native species) in several ways • Competition -- the introduced species may outcompete the native species for its habitat.• Predation - the introduced species may be a predator of the native species.• Pathogenesis - the introduced species may be a pathogen exposed to a new species (Chestnut blight is a prime example).• Also known as invasive species.• Exploitation by humans – • Hunting - many island species were lost to hunting. This also includes hunting of species because they are considered pests (elimination of wolves and bears from most of their natural range in North America are examples). • In order to alleviate this it is recommended that the practice of Subsistence hunting – hunting only to acquire basic necessities for survival; makes relatively few demands on the environment.• Exploitation by humans – • Fishing - many once very abundant marine species are on the verge of extinction. • This also includes extinctions caused by "by-catch" or incidental takes. The major cause of sea turtle decline now is not hunting the turtles, rather it is the deaths caused by drowning when the turtles become entangled in fish nets. Dolphins experienced similar problems with this as well. • Exploitation by humans –

• Harvesting from the forest (rare herbs are in this group), and • Live trade in both plants (orchids) and animals (exotic snake and bird species as pets).• Threatened Species: A species whose population size is rapidly declining.• Endangered Species: A species whose population size is rapidly declining and will become extinct if the trend continues.• Habitat Fragmentation: The splitting of ecosystems into smaller fragments. When habitats are fragmented they cannot support as much biodiversity.• Habitat Corridors: Natural strips that allow the migration of organisms from one area to another in order to overcome habitat fragmentation and loss of habitat.• Pollution: Pollutants: harmful materials of human origin that can enter the biosphere through the land, air or water and alter organisms.• Often it is local activity that has important effect. For example, strip mining can acidify lakes due to runoff from rock brought to surface as part of mining activity • Human activities can now produce global effects too. Acid rain can be the result of burning of fossil fuels (particularly coal) many miles from where the acids are deposited.• Biological Magnification: Increasing concentration of a harmful substance in organisms at higher trophic levels in a food chain or food web. For examples: the levels of DDT seen in bald eagles before it was banned.Renewable and Nonrenewable Resources:• “The Tragedy of the Commons”: The notion that any resource that is open to everyone – such as the air or parts of the oceans – will eventually be destroyed because everyone can us the resource, but no one is responsible for preserving it.• Renewable Resources: Resources that can regenerate quickly and that is replaceable.• Nonrenewable Resources: Resources that cannot be replenished (replaced) by natural processes.• The classification of a resource as renewable or nonrenewable depends on its context. Although a single tree is renewable, a population of trees in a forest ecosystem (such as the tropical rainforest) – on which a community of organisms depends – may not be renewable, because that ecosystem may change forever once those trees are gone.• Sustainable Use: A way of using natural resources at a rate that does not deplete them. Sustainable practices a based on principles of ecology and economics.• Land Resources: properly managing the land to prevent soil erosion and desertification are important.• Land Resources:• Soil erosion: the removal of soil by water, wind or tilling (farming).• Land Resources:• Desertification: Desertification became well known in the 1930's, when parts of the Great Plains in the United States turned into the "Dust Bowl" as a result of drought and poor practices in farming, although the term itself was not used until almost 1950. During the dust bowl period, millions of people were forced to abandon their farms and livelihoods. Greatly improved methods of agriculture and land and water management in the Great Plains have

prevented that disaster from recurring, but desertification presently affects millions of people in almost every continent..• Ocean Resources: We obtain many resources, particularly food, from the oceans. But recently we have begun to deplete these resources. This is a good example of “The Tragedy of the Commons,” because managing the oceans is a difficult to manage international problem. Recently the practice of aquaculture has been used to help.• Air Resources: Air is another common resource that is taken for granted. Today we see problems with air pollution, including smog, and acid rain.• Air Resources:• Smog:• Smog is caused by a reaction between sunlight and emissions mainly from human activity.• Classic smog results from large amounts of coal burning in an area and is caused by a mixture of smoke and sulphur dioxide. In the 1950s a new type of smog, known as photochemical smog, was first described. This is a noxious mixture of air pollutants.• Air Resources:• Acid rain.• Acid rain occurs when sulfur dioxide and nitrogen oxides are emitted into the atmosphere, undergo chemical transformations and are absorbed by water droplets in clouds. The droplets then fall to earth as precipitation. This can increase the acidity of the soil, and affect the chemical balance of lakes and streams. • Acid rain accelerates weathering in carbonate rocks and accelerates building weathering. It also contributes to acidic rivers, streams, and damage to trees at high elevation. • Water Resources: Though water is renewable, it is in limited supply. Therefore, water must be protected from pollution and the ever increasing demand for it must lead to its conservation.Conserving Biodiversity:• Conservation: The wise management of natural resources, including the preservation of habitats and wildlife.• Today, conservation efforts focus on protecting entire ecosystems as well as single species. Protecting an ecosystem will ensure that the natural habitats and the interactions of many different species are preserved at the same time.• Reintroduction Programs: Releasing organisms into an area where their species once lived.• Captivity: When members of a species are held by people in zoos or other conservation facilities. One example of this is captive breeding programs in the pet trade today, where many of the individuals for sale are from captivity and not taken from the environment. • This is what officials at the Georgia Aquarium hope to do with the whale sharks.Charting a Course for the Future:• As we enter the twenty-first century, many biologists are concerned about the biological effects of two types of global changes: the thinning, or depletion, of the ozone layer and global warming.

• The Ozone Layer is a concentration of the gas ozone (O3) in the atmosphere that absorbs much of the UV radiation from sunlight. There are gaps (“holes”) in the ozone layer at the poles caused by chemicals called chlorofluorocarbons (CFCs) that were once widely used as propellants and coolants.• The greenhouse effect is the natural situation of carbon dioxide, methane, water vapor and a few other atmospheric gases that trap infrared radiation and heat energy in the atmosphere and maintain Earth’s temperature ranges.• The term used to describe the increase in average temperatures of the biosphere is called global warming. It is most likely due to human activities that have added water vapor, carbon dioxide, methane, ozone, CFCs and nitrogen oxide to the atmosphere. • This is increasing the greenhouse effect and leading to an increase in temperatures worldwide. • Any change in the Earth’s climate could have profound effects on the biosphere. Including at the polar icecaps.• It is essential that we keep the biosphere healthy if humans and the Earth are to survive.