Ecology Unit Study Guide – Teacher Version with Answer Key
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List several examples of a habitat. Cave, soil, dead log in a forest, fish aquarium, mouse hole
A living plant, animal or microbe is what? organism
Define biodiversity. The diversity of a species in a given area
Define Ecosystem. A community of organisms interacting with abiotic environmental factors
With regards to the carbon cycle, what would be the results of the burning and clearing of a tropical
rain forest. Global warming would increase; less oxygen available, a decrease in biodiversity
What is the ideal pH for freshwater biomes? A neutral pH
What activities would have a negative impact on a habitat? A snow avalanche, resurfacing a road,
off-roading, a forest fire, a nuclear explosion
How is the number of organisms in both lakes and ocean ecosystems determined? By the amount of
available nutrients and sunlight
Explain how a top predator may increase the diversity of species lower on the food chain. Decreasing
competition
The next two items refer to the economically valuable forest of the Pacific Northwest. Douglas fir,
cedar and hemlock are the principal trees of the region. Characteristics of each are as follows.
Douglas Fir
Cedar and Hemlock
Seedlings die in shade
Seedlings grow on ashes
Seeds have wings
Seedlings grow in the shade
Seedlings do not grow on ashes
Seeds are not winged
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Young cedar trees require what? Shade and an area without ashes
Which trees would have a survival advantage following a fire? Douglas Fir
Define nonnative species. Invasive, not normally found in the area, introduced into an area by humans
Define biological magnification. The phenomenon in which organisms pick up and concentrate
pollutants they cannot metabolize
14. What is the most common explanation for population growth by a non-native species? They have
found many unoccupied niches.
Study the graph below and answer the questions that follow.
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15. What does the graph show about the earth’s atmosphere? As the concentration of carbon dioxide
increases, the temperature also increases.
16. Most scientists are concerned that global warming is the result of an increase in the concentration of
carbon dioxide in the atmosphere.
17. Which environmental factors are looked at when monitoring human pollution? Air quality, water
quality, ocean currents
18. The maintenance of a self-sustaining ecosystem requires what? Cycling of materials between
organisms and their environment
19. Why does each successive feeding level in a pyramid of energy have less biomass? Carnivore
biomass is less than producer biomass as a result of energy being lost as it flows from producers to
carnivores.
20. What is the most likely order of succession in the repopulation of an area? lichens -> grasses->
shrubs-> trees
21. According to the graph which one is a carnivore? Hawk, snake, lizard, bird, mouse
22. According to the food web, which of these describes the relationship between the snake and the
chipmunk? Predator-prey
23. Which combination of organisms shows a single food chain in this web? various
24. The transition from a tropical rain forest to a grassland is marked by fewer and fewer trees. This is
most likely caused by a decrease in rainfall?
25. Sea otters eat sea urchins. Sea urchins eat kelp, a type of brown algae. What might be the short-term
effect on the ecosystem if great numbers of sea otters were removed from this environment? Increase
in sea urchin population & decrease in kelp population
26. What is the ultimate source of energy for the majority of life on Earth? The sun
27. Many more species of plants and animals live in a tropical forest than live in a desert. This difference
is most likely due to the fact that, compared to a tropical forest, a desert contains less water.
28. What part of the ecosystem is not recycled through the Earth’s ecosystems? energy
29. According to the graph, the human population remained essentially unchanged for thousands of years.
30. List several examples of a mutalistic relationship. various
31. Natural populations numbers increase and decrease around the carrying capacity when they reach a
steady state.
32. A group of similar-looking organisms that breed with each other and produce fertile offspring make
up a population.
33. Rabbits introduced into Australia over 100 years ago have become a serious pest to farmers. Rabbit
populations increased so much that they displaced many native species of plant eaters. What is the
most logical explanation for their increased numbers? Few effective predators
34. What does A stand for in the chart above? mutualism
35. Give an example of B in the chart above? various
36. What does C stand for in the chart above? parasites
37. If a population grows larger than the carrying capacity of the environment, the death rate may rise.
38. Nutrients move through the biosphere in nutrient or biogeochemical cycles.
39. As water cycles through the ecosystem, which process returns it to the atmosphere? evaporation
40. Local and federal legislation have placed limits on the amount of nitrogen containing fertilizers to be
tolerated in field run-off into a lake. The reason for this legislation is that run-off of the fertilizers
would most likely produce an increase in algal growth.
41. What does each of the letters on the chart represent? A – evaporation, B – condensation, C –
precipitation, D – ocean/water
42. Probably the most important factors affecting the distribution of biomes are climate & climax
communities
43. Complete burning of plant material returns carbon primarily to what? atmosphere
44. The action of decomposers in the nitrogen cycle most directly aids in the restoration of nitrogen
compounds to the soil.
45. What is the role of NO3 in the cycle? Used by plants for growth.
46. In the material cycle above, which processes are represented by letters A and B? A – cellular
respiration, B - photosynthesis
47. Which level of the pyramid represents the largest percentage of available energy? algae
48. According to the chart, which organisms are the top carnivores in the river ecosystem? trout
49. According to the chart, if the trout were overfished, which population of organisms would most
likely increase as a direct result? minnows
A small, cold creek flows through a dense forest. The trees that line the banks of the creek provide shade
for most of the day. Algae grow well only in the few areas of the creek that receive direct sunlight for
several hours each day. Most of the food energy enters the creek ecosystem in the form of dead leaves
that fall from the trees.
50. A fire swept through the forest, burning all the leaves but leaving the trees standing. This greatly
increased the amount of direct sunlight reaching the creek, but did not produce more than the usual
amount of erosion. As a result of the fire, which of these most likely increased in the creek? algae