Chapter 4, Section 1

Ecosystems: Everything is Connected

An ecosystem is all of the organisms living in an area together with their physical environment.Oak ForestCoral ReefParkVacant Lot

Ecosystems do not have clear boundaries. Things move from one ecosystem to another.

Pollen can blow from a forest into a field, soil can wash from a mountain into a lake, and birds migrate from state to state.

Defining an Ecosystem

Biotic factors are environmental factors that are associated with or results from the activities of living organisms .Plants (living or dead)Animals (living or dead)Waste Products

Abiotic factors are environmental factors that are not associated with the activities of living organisms .AirWaterRocksLightTemperature.

Biotic and Abiotic Factors

In order to survive, ecosystems need five basic components: EnergyMineral nutrientsWaterOxygenLiving organisms.

Ecosystems contain biotic and abiotic factors.If one part of the ecosystem is destroyed or

changes, the entire system will be affected.

Components of an Ecosystem

Organisms – Any form of life.

Species – Groups of organisms that resemble one another in appearance, behavior, chemistry, and genetic makeup

Every organism is a member of a species.

Species are groups of organisms that are closely related can can mate to produce fertile offspring.

Organisms and Species

Insects751,000

Other animals281,000

Fungi69,000

Prokaryotes4,800

Plants248,400

Protists57,700

Known species1,412,000

Members of a species interact in groups called populations.

Populations of different species living and interacting in an area form a community.

Populations are groups of organisms of the same species that live in a specific geographical area and interbreed.All the members of the same species that live in the same

place at the same time.

A community interacting with its physical environment of matter and energy is an ecosystem.

Populations, Communities, & Ecosystems

Fig. 3-2, p. 51

Communities

Subatomic Particles

Atoms

Molecules

Protoplasm

Cells

Tissues

Organs

Organ systems

Organisms

Populations

Populations

Communities

Ecosystems

Biosphere

Earth

Planets

Solar systems

Galaxies

Universe

Organisms

Realm of ecology

Ecosystems

Biosphere

Habitats are places where an organism usually lives.

Every habitat has specific characteristics that the organisms that live there need to survive. If any of these factors change, the habitat changes.

Organisms tend to be very well suited to their natural habitats.

Animals and plants usually cannot survive for long periods of time away from their natural habitat.

Habitats

1. List the abiotic and biotic factors you see in the northern ecosystem in Figure 3 (page 100).

2. Describe a population not already mentioned.

3. Describe which factors of an ecosystem are not part of a community.

4. Why might a scientist say that an animal is becoming rare because of habitat destruction?

CHECK POINT

Chapter 4, Section 2

Evolution

Look at Figure 7 (page 103)

Discuss the characteristics that you think help the chameleon when it hunts.

Activity

1809, France, Jean Baptiste Lamarck

Proposed a hypothesis for how organisms change over generations.Over the lifetime of an individual, physical features increase

in size because of use or reduce in size because of disuse.Changes are passed on to offspring.

Lamarck was correct in thinking that the change in species is linked to the “physical conditions of life.”

Lamarck was incorrect in thinking that changes that occur during the lifetime of an individual organism are passed on directly to their offspring.

Evolution, Lamarck’s Theory

1859, England, Charles DarwinWhile on a voyage (HMS Beagle) noticed:

Organisms in one population differ slightly from each other in form, function and behavior.

Some of the differences are hereditary.Proposed a hypothesis for how species change

over timeThe environment exerts a strong influence over

which individuals survive to produce more offspring.Some individuals, because of certain traits, are

more likely to survive and reproduce than other individuals.

Evolution, Darwin’s Theory

“Can we doubt…that individuals having any advantage, however slight, over others would have the best chance of surviving and of procreating their kind? On the other hand, we may feel sure that any variation in the least degree injurious would be rigidly destroyed. This preservation of favorable variations, I call Natural Selection.”

--- Charles Darwin

Natural selection is the process by which individuals that have favorable variations and are better adapted to their environment survive and reproduce more successfully than less well adapted individuals do.

Darwin proposed that over many generations, natural selection causes the characteristics of populations to change.

Evolution is a change in the characteristics of a population from one generation to the next.

Evolution and Natural Selection

Darwin thought that nature selects for certain traits, such as sharper claws, because organisms with these traits are more likely to survive.

Over time, the population includes a greater and greater proportion of organisms with the beneficial trait.

As the populations of a given species change, so does the species.

Adaptation – an inherited trait that increases an organism’s chance of survival.

Evolution and Natural Selection

All populations have genetic variation.

The environment presents challenges to successful reproduction.

Individuals tend to produce more offspring than the environment can support.

Individuals are better able to cope with the challenges presented by their environment tend to leave more offspring than those individuals less suited to the environment.

Basic Rules of Natural Selection

13 or 14 separate species of finches collected from the Galapagos Islands

All birds are about the same size and color.

Most important differences between species are in the size and shape of their beaks.

Each beak is highly adapted to different food sources.

Darwin’s Finches

Large beaks – Crush seeds in beaks

Narrow beaks – Eat insects

Short, stubby beak – Eats seeds and few insects

Sharp beaks – Poke holes in food or pick insects out of cactus

Darwin’s Finches

Another Example…

Coevolution - The process of two species evolving in response to long-term interactions with each other is called.

An example is the Hawaiian honeycreeper (page 106), which has a long, curved beak to reach nectar at the base of a flower. The flower has structures that ensure that the bird gets some pollen on its head.

When the bird moves the next flower, some of the pollen will be transferred, helping it to reproduce.

Coevolution

The honeycreeper’s adaptation is along, curved beak.

The plant has two adaptations:The first is the sweet nectar, which attracts the

birds.The second is the flower structure that forces

pollen onto the bird’s head when the bird sips nectar.

Coevolution

Artificial selection - the selective breeding of organisms, by humans, for specific desirable characteristics.

Examples:Dogs have been bred for certain

characteristics.Fruits, grains, and vegetables are also

produced by artificial selection. Humans save seeds from the largest, and sweetest fruits. By selecting for these traits, farmers direct the evolution of crop plants to produce larger, sweeter fruit.

Artificial Selection

Resistance - the ability of an organism to tolerate a chemical or disease-causing agent.

An organism may be resistant to a chemical when it contains a gene that allows it to break down a chemical into harmless substances.

Humans promote the evolution of resistant populations by trying to control pests and bacteria with chemicals.

Evolution of Resistance

A pesticide is sprayed on corn.It kills most of the grasshoppers.The grasshoppers that survive have a gene that

protects them from the pesticide.The surviving insects pass on the resistance

gene to their offspring.Each time the corn is sprayed, more resistant

grasshoppers enter the population. Eventually the entire population will be

resistant, making the pesticide useless.

Pesticide Resistance

Pesticide Resistance

1. Describe several ways in which artificial selection can benefit humans.

2. Explain how a population of insects becomes resistant to a pesticide.

3. Describe the role of the environment in the theory of natural selection.

4. A population of rabbits evolves thicker fur in response to a colder climate. Is this an example of coevolution? Explain your answer.

CHECK POINT