CP Biology
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Unit 2C: Ecological Biochemistry
Study Guide
Community Interactions include predation, competition, herbivory, and
symbioses.
Competition: Competition occurs when organisms try to use the same limited resources.
Predation, Herbivory, and Keystone Species Predator-prey and herbivore-plant
interactions help shape communities.
Predation occurs when one organism (the predator) captures and eats another (the prey).
Herbivory is an interaction that occurs when an animal (the herbivore) feeds on producers
(such as plants).
Sometimes changes in the population of a single species, often called a keystone species, can
cause dramatic changes in the structure of a community.
Symbioses Symbiosis occurs when two species live closely together in one of three ways:
mutualism, commensalism, or parasitism.
In mutualism, both species benefit from the relation ship.
In parasitism, one species benefits by living in or on the other and the other is harmed.
In commensalism, one species benefits and the other is neither helped nor harmed
Write the letter of the correct answer on the line at the left.
1. A lion eating a zebra is an example of
A. herbivory.
C. predation.
B. habitat destruction.
D. a keystone species.
2. A cow eating grass is an example of
A. herbivory.
C. habitat destruction.
B. predation.
D. a keystone species.
3. A keystone species is one that
A. eats a mixture of plants and animals.
B. is introduced into a community after a major disturbance.
C. causes the amount of diversity in a community to decrease.
D. helps to stabilize the populations of other species in the community.
Match the symbiotic relationship with the best description
a. parasitism
b. mutualism
c. commensalism
____B___4. Symbiotic relationship between two organisms where both benefit
____A___5. Symbiotic relationship between organisms where one benefits and one is harmed
____C___6. Symbiotic relationship between organisms where one benefits and the other is not
affected
The Water Cycle
Condensation
Precipitation
Evaporation
Transpiration
Runoff
Label the steps of the water cycle in the diagram above and describe each step.
7.
Evaporation- liquid water becomes water vapor (gas)
8. Condensation- water vapor (gas) becomes liquid
9. Precipitation- condensed water falls to the ground as rain, snow, etc.
10. Transpiration- water evaporates off the leaves of plants
11. Run off- water flows downhill to bodies of water
12. Ground water- water soaked into the ground
13. Which of the following is NOT part of the water cycle?
a. evaporation
c. photosynthesis
b. precipitation
d. condensation
Fill in the blanks with terms from the water cycle.
14. The continuous movement of water into the air, onto land, and then back to water sources is
known as the __water cycle_______________.
15. Rain, snow, sleet or hail that falls from clouds is called ____precipitation_____________.
16. The process in which liquid water is heated by the sun and then rises into the atmosphere as
water vapor is known as _________evaporation____________.
Answer “yes” or “no” for questions 17 and 18.
17. Are materials recycled through an ecosystem? ____yes______
18. Is energy recycled through an ecosystem?
_____no_______
19. For the following 3 steps in the carbon cycle, determine if the process increases or decreases
the amount of CO2 and O2 in the environment.
Process
CO2
O2
Cellular Respiration:
increase
decrease
Photosynthesis:
decrease
increase
Burning fossil fuels:
increase
decrease
For questions 20 – 23, choose if each statement describes photosynthesis or cellular respiration.
a. photosynthesis
b. cellular respiration
__A___20. Requires energy from the sun
__A___21. Converts CO2 from the atmosphere into food energy (glucose)
__B___22. Takes place in all organisms
__B___23. Converts glucose into ATP and releases CO2
Quick reminder – remember the equations for cellular respiration and photosynthesis!
sunlight
Photosynthesis:
6CO2 + 6H20  C6H12O6 + 6O2
Cellular respiration:
C6H12O6 + 6O2  6CO2 + 6H20 + ATP
24. The nitrogen cycle is driven by what unicellular organisms?
bacteria
25. Organisms need nitrogen so that they can produce which 2 important macromolecules?
Proteins and nucleic acids
26. The carbon in coal, oil, and natural gas came from
A. the combustion of fossil fuels.
B. the remains of dead organisms.
C. carbon-fixing bacteria in swamp soil.
D. carbon dioxide dissolved in ocean water.
27. How does most of the carbon in an organism’s body return to the environment after the
organism dies?
A. Decomposers break the body down into simpler compounds.
B. Heat from the sun causes the carbon in the body to evaporate.
C. Geological processes cause the body to turn into a fossil fuel.
D. Rainwater dissolves the carbon in the body and carries it to the ocean.
28. Human processes (such as burning fossil fuels) mainly contribute to the
A. release of large amounts carbon dioxide into the atmosphere.
B. decrease of the total amount of carbon found on Earth.
C. depletion of carbon dioxide reserves in the atmosphere.
D. increase in the amount of carbon contained in rock materials.
29. _______________ is the process in which certain bacteria convert nitrogen gas into usable
forms of nitrogen.
a. denitrification
b. nitrogen fixation
c. decompostion
30. ______________ is the process by which some soil bacteria convert nitrates back into
nitrogen gas.
a. nitrogen fixation
b. denitrification
c. decomposition
31. All organisms require nitrogen to make amino acids, which in turn are used to build proteins.
a. true
b false
32. Plants and animals can absorb nitrogen gas directly from the atmosphere.
a. true
b. false
33. What role do decomposers play in both the carbon and nitrogen cycles?
Decomposers break down dead organisms, returning their molecules/nutrients to the soil where
they can be used by other organisms (plants and bacteria).
34. How do humans affect the nitrogen cycle?
The addition of fertilizers adds excess nutrients to the soil. These excess chemicals/nutrients
runoff in the water to rivers and lakes and could cause eutrophication (the over-growth of algae
that disrupts the aquatic ecosystem).