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Which statement best describes extinction?
A) Extinction is very rare and was not seen at all until the last few hundred years.
B) Extinction is most common for generalist species that have large niches.
C) Extinction is always caused by human interferences to an ecosystem.
D) Extinction events have happened throughout all of Earth’s long history.
E) Extinction increases Earth’s biodiversity over long time periods
I am torn between D and E. It could be E because my text book says “The balance between the evolution of new species and extinction of existing species is what creates earth’s biodiversity.” So I don’t know which one best describes extinction. What do you think?

The study of the interaction of living organisms with each other and with their physical environment is called
A ecology. B health.
C geology. D economy.
2. A group of organisms of different species living together in a particular place is called a
A habitat. B community.
C biome. D population.
3. All organisms in an ecosystem are linked together in a network of interactions. This quality is called
A geochemical processes. B isolation.
C communication. D interdependence.
4. Ecological models are useful for all of the following purposes except
A evaluating proposed solutions to environmental problems.
B testing predictions about future ecological changes.
C making predictions about future ecological changes.
D accounting for all the variables that exist in a real environment.
5. The specific physical location in which a given species lives is called its
A climate. B habitat.
C community. D abiotic factor.
6. The areas of an organism’s tolerance curve that lie at the extreme high or low for an environmental variable represent the
A optimal range of the environmental variable for the organism.
B zones of efficient performance by the organism.
C range of the environmental variable preferred by the organism.
D zones of poorest performance by the organism.
7. Which of the following is not an way that organisms deal with unfavorable environmental conditions?
A dormancy B body temperature regulation
C interdependence D migration
8. An organism’s niche includes
A what it eats. B where it eats.
C when it eats. D All of the above
9. Which of the following would not be included in a description of an organism’s niche?
A when it reproduces
B its trophic level
C its number of chromosomes
D the humidity and temperature it prefers
10. Organisms that manufacture organic nutrients for an ecosystem are called
A consumers. B predators.
C omnivores. D producers.
11. cows : herbivores ::
A algae : consumers B plants : producers
C horses : carnivores D caterpillars : producers
12. When an organism dies, the nitrogen in its body
A can never be reused by other living things.
B is immediately released into the atmosphere.
C is released by the action of decomposers.
D All of the above
13. Refer to the illustration above. The photosynthetic algae are
A decomposers. B producers.
C parasites. D consumers.
14. Refer to the illustration above. The diagram, which shows how energy moves through an ecosystem, is called a
A habitat net. B food chain.
C food web. D trophic level.
15. Refer to the illustration above. Among all of the food chains, the organisms at the highest trophic level are
A the krill. B the crabeater seals.
C the algae. D the killer whales.
16. In a food web, which type of organism receives energy from every other type?
A producer B carnivore
C decomposer D All of the above
17. Refer to the illustration above. On the pyramid, animals that feed on plant eaters are no lower than
A level 4. B level 1.
C level 3. D level 2.
18. Refer to the illustration above. How much energy is available to the organisms in level 3?
A all of the energy in level 1 plus the energy in level 2
B all of the energy in level 1 minus the energy in level 2
C about 90 percent of the energy in level 2
D about 10 percent of the energy in level 2
19. In an ecological energy pyramid, animals that feed on plants are at least in the
A third trophic level. B second trophic level.
C first trophic level. D fourth trophic level.
20. The number of trophic levels in an ecological energy pyramid
A never exceeds three.
B is limitless.
C is impossible to count because energy is lost at each trophic level.
D is limited by the amount of energy that is lost at each trophic level.
21. In going from one trophic level to the next higher level,
A the number of organisms increases.
B the amount of usable energy increases.
C the amount of usable energy decreases.
D None of the above
22. Refer to the illustration above. At each trophic level, the energy stored in the organisms in that level is
A about 10 percent of the energy in the level below it.
B about 10 percent of the energy in the level above it.
C about 50 percent of the energy in the level above it.
D about 50 percent of the energy in the level below it.
23. Water and minerals needed by all organisms on Earth pass back and forth between the biotic and abiotic portions of the environment in a process called
A a biogeochemical cycle.
B a trophic pathway.
C a trophic cycle.
D a biochemical pathway.
24. Precipitation and evaporation are important components of the
A nitrogen cycle. B water cycle.
C carbon cycle. D All of the above
25. In the nitrogen cycle, plants use nitrates and nitrites to form
A proteins and nucleic acids. B ammonia.
C fats. D nitrogen gas.

1. The organisms of one species living together in the same place at the same time are a ____.
community
population
niche
all of the above
2. Which process uses oxygen in plants, algae, and animals? (1 point)
transpiration
photosynthesis
chemosynthesis
respiration
3. During photosynthesis, light energy becomes ____ energy. (1 point)
soil life
chemical
mechanical
pyramid
4. Which of the following eats consumers?
herbivore
bacteria
fungi
5. Nitrogen in the soil is used by ____.
plants
animals
both a and b
neither a nor b
6. As you move upward, from level to level, in an energy pyramid, energy ____. (1 point)
decreases
increases
stays at the same level
is destroyed
7. Of the following, which is NOT a freshwater ecosystem? (1 point)
lake
pond
estuary
swamp
Completion
8. The portion of Earth that supports life is called the ____________________.
9. The burrow a chipmunk digs under a patio stone is an example of a(n) ____________________.
(1 point)
10. Organisms that can use the energy from an outside source such as the Sun to create energy-rich molecules are called ____________________.
11. A symbiotic relationship in which both organisms benefit is called ____________________.
12. Average weather conditions over time are called ____________________.
(1 point)
Short Answer
13. Compare and contrast a community and an ecosystem.
14. Why must a producer be at the base of every food chain?
15. Describe the relationship between CO2 and oxygen in the process of photosynthesis. How does this benefit both plants and animals?
16. Compare a climax community to a pioneer species.
17. List at least three ways in which grassland and tundra biomes are similar.

Just seems so odd that there niche in the ecosystem is to eat tons of such small creatures

2. The stable ecosystem that develops due to succession _____.
(1 point)
is called a niche
is always a forest
is called a climax community
never changes
Figure 3-6
3. Look at the graph in Figure 3-6. Approximately how many hours of sunlight should these plants receive each day in order to make them grow at their optimum level?
(1 point)
4
12
16
20
4. Water temperature and light are two ____________________ factors that affect the tolerance range of organisms in a lake.
(1 point)
5. Tropical rain forest and ____________________ biomes are both characterized by a thin layer of nutrient-poor topsoil that can support only shallow-rooted plants.
(1 point)
6. Fires, natural disasters, and human intervention are possible causes of ____________________.

A niche is an organism’s role in an ecosystem. What is the niche of a brown bear in a temperate rain forest ecosystem?