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Unit 6: Matter and Organisms in Ecosystems Study Guide – Answer Key
Use a separate sheet of paper to answer the questions on this worksheet.
1. What is a biotic factor?
a. All living or once living parts of an ecosystem that directly or indirectly
affect the environment.
2. Give an example of a biotic factor.
a. Populations of deer, foxes, trees, grass, trees, produces, consumers,
decomposers, interspecies competition, communities of deer, fish,
rabbits, dandelions, etc.
3. What is an abiotic factor?
a. All of the non living or NEVER alive parts of an ecosystem.
4. Give an example of an abiotic factor.
a. Sunlight intensity, cold or warm temperatures, weather systems, how
long the sun is out, increases or decreases in precipitation, gas in the air,
streams, clouds, rocks, etc.
5. What are limiting factors?
a. Any biotic or abiotic factor that limits the number of individuals in a
population.
6. Give an example of a limiting factor.
a. The amount of mountain lions in an area that feed on deer. The amount
of sunlight that a plant gets will limit the amount of plants in an area.
The amount of water in a pond ecosystem can support thirty large
mouth bass.
7. How does a limiting factor keep a population from growing?
a. A limiting factor keeps a population from growing because it restricts
the amount of resources, abiotic and biotic factors, a population of
organisms needs to survive.
8. Describe a change of a biotic factor in an ecosystem.
a. A seasonal migration of birds to a southern ecosystem in the springtime
will cause the bug population to decrease. A population of rabbits
decreases because of a lack of clovers in an area. The coyote population
decreases as well because; there aren’t enough rabbits to feed all of the
coyotes in the area.
9. Describe a change of an abiotic factor in an ecosystem.
a. The seasonal changes in temperature cause the raspberry population to
decrease in the winter and fall, the raspberry population will increase in
the summer and spring. The amount of sunlight affects the growth of
ferns in a forest ecosystem.
10. What are the levels of ecological organization in order from smallest to
largest?
a. Species, population, community, ecosystem, and biosphere.
11. What is a species? Give an example of one.
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a. A group of organisms that share similar characteristics and can
reproduce among themselves. A species is a biotic factor. An example of
a species is a white squirrel.
12. What is a population? Give an example of a population.
a. A population is a group of individuals that live together in the same
area at the same time. An example of a population would be all of the
clams that live and breed in a shallow ocean ecosystem. A population is
a biotic factor.
13. What is a community? Give an example of a community.
a. A community is a group of cooperating populations. So basically it is all
of the living (biotic) parts of an ecosystem. An example of a community
would be a pine tree, beaver, hawk, and fish living in a riverside
ecosystem.
14. What is an ecosystem? Give an example of an ecosystem.
a. An ecosystem is a community (biotic) and all of its non – living (abiotic)
parts of the environment. An example of an ecosystem would be a fish
pond with natural sunlight, water plants to recycle carbon dioxide and
water, fish to eat some of the water plants and use the gas emitted.
15. Of all of the levels of ecological organization, which level contains abiotic and
biotic factors?
a. The only levels of ecological organization that contain biotic and abiotic
factors are ecosystems and biomes.
16. What are some actions that humans can do to improve ecological impacts on
an ecosystem?
a. Humans can replant trees where they have been cut down and plant a
cover crop in a farm field to let the land rest and not erode that year.
Reforestation and covercropping are two ways to reclaim an ecosystem.
17. What are some examples of human disruptions of an ecosystem?
a. Pollution, habitat destruction, causing a forest fire, overhunting, over
fishing, introducing a non – native species into a new ecosystem,
destroying natural habitats.
18. What are some examples of natural disruptions of an ecosystem?
a. Tornadoes, Hurricanes, snowstorms, drought, floods, can all cause an
ecosystem disruption.
19. What are three ways in which an aquatic ecosystem can be disrupted?
a. Unregulated pesticide usage can cause massive fish deaths, All of the fish
have been removed from the ecosystem, and a non – native species with
no natural enemies can be introduced into the ecosystem.
20. What does covercropping and reforestation accomplish for an ecosystem?
a. Covercropping and reforestation prevents erosion and reclaims lost
ecosystems.
21. How could an organism be added to an endangered or extinction list?
a. Usually an organism will be added to the endangered or extinction list if
the habitat has been destroyed or the organism has been overhunted,
overharvested or overfished.
22. What happens to an ecosystem after secondary succession occurs?
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a. The land already has soil, so tall grasses and non – woody plants grow,
then shrubs are added in, followed by fast – growing pine trees and then
eventually hard- wood tress start to grow. Animals move back into the
area and all biotic factors adapt to their environment.
23. Why is it not a good idea to bring a non-native species into an ecosystem?
a. It is not a good idea to bring a non – native species into an ecosystem
because it competes with the native species for resources and it has no
natural enemies to kill the non – native species off.
24. Why would the removal of a keystone species be detrimental to an
ecosystem?
a. Yes, because a keystone species is a species that contributes to the
diversity of life in an ecosystem. For instance a deer eats berries and
emits waste with berry seeds, which are then planted where the deer
“went”. The deer’s role is to help spread berry bushes throughout the
forest ecosystem. A prairie dog digs burrows in the ground, these
burrows act as other homes to other animals, such as an owl, a
badger, rabbit, snakes, salamanders and insects
25. How could an organism not be considered a keystone species in an
ecosystem?
a. An organism would be NOT be considered an keystone species if it
was a non-native species to that area. For example a Burmese Python
living in the Florida everglades would be a great example.
26. What would happen if humans removed a species from an ecosystem?
a. If humans removed a species from an ecosystem, the stability of the
ecosystem could be damaging to other biotic factors in the community.
27. Why do only certain species live in specific ecosystems?
a. Only certain species live in specific ecosystems because they are adapted
to the specific environment in which they live. For example the polar
bear in the northern part of the U.S. and Canada.
28. What is a niche?
a. A niche is a role that an organism plays in an ecosystem. For instance a
honeybees niche is to pollinate as many flowers as possible. A beaver
creates a dam, which provides an ecosystem / habitat for many other
lake species.
29. Areas with many niches show an example of what term?
a. Areas with many niches show that an ecosystem is very healthy with
great biodiversity.
30. Why should humans reduce the use of pesticides?
a. Reduction in pesticides will increase the biodiversity in an area.
31. What would be a disadvantage of removing weeds from an urban area?
a. It can destroy the habitat for many beneficial insects.