An ecosystem is all of the organisms living in an area
together with their physical environment.
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
Biotic factors are environmental factors that are
associated with or results from the activities of living
Plants (living or dead)
Animals (living or dead)
Abiotic factors are environmental factors that are not
associated with the activities of living organisms .
In order to survive, ecosystems need five basic
Ecosystems contain biotic and abiotic factors.
If one part of the ecosystem is destroyed or
changes, the entire system will be affected.
Organisms – Any form of life.
Species – Groups of organisms that resemble one
another in appearance, behavior, chemistry, and
Every organism is a member of a species.
Species are groups of organisms that are closely
related can can mate to produce fertile offspring.
Known species 281,000
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.
Solar systems Biosphere
Organisms Realm of ecology
Fig. 3-2, p. 51
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
Animals and plants usually cannot survive for long
periods of time away from their natural habitat.
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?
Look at Figure 7 (page 103)
Discuss the characteristics that you think help the
chameleon when it hunts.
1809, France, Jean Baptiste Lamarck
Proposed a hypothesis for how organisms change over
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.
1859, England, Charles Darwin
While 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
The 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.
“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
Evolution is a change in the characteristics of a
population from one generation to the next.
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
Adaptation – an inherited trait that increases an organism’s
chance of survival.
All populations have genetic variation.
The environment presents challenges to successful
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
13 or 14 separate species of finches collected from the
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.
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
Coevolution - The process of two species evolving in
response to long-term interactions with each other is
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.
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.
Artificial selection - the selective breeding of
organisms, by humans, for specific desirable
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.
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
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
Each time the corn is sprayed, more resistant
grasshoppers enter the population.
Eventually the entire population will be
resistant, making the pesticide useless.
1. Describe several ways in which artificial selection can
2. Explain how a population of insects becomes resistant to
3. Describe the role of the environment in the theory of
4. A population of rabbits evolves thicker fur in response to
a colder climate. Is this an example of coevolution?
Explain your answer.