Environmental Science-KEY
Study Guide
Ch. 5
1. What type of succession occurs after a forest fire? Secondary
2. In succession, when are the most pioneer species found?
Pioneer species are the first species to appear in a succession.
3. What type of species do you find at the top of a pond? Many different kinds of species-great
diversity.
4. What type of species do you find at the bottom of a pond? Decomposers that feed on dead
organisms
5. On a newly formed volcanic island, list the order of species that will grow in primary succession.
Bare rock, lichens, small annual plants, perennial herbs and grasses, shade intolerant trees
6. Give an example of a pioneer species. Lichen
7. Define ecological succession. The series of predictable changes that occurs in a community over
time
8. When does primary succession begin? Anytime there is no previous ecosystem, such as when a
new island is formed from lava flow.
9. What is one difference between primary and secondary succession? Secondary succession
begins on soil and primary succession begins on newly exposed surfaces.
10. Where do consumers get their energy? From eating other organisms
11. Which kind of organism obtains energy only from producers? Herbivores
12. Which gas makes up 78 percent of our atmosphere but can be used by plants only when
transformed by bacteria first? Nitrogen
13. What kind of natural disaster helps some forest communities by allowing some trees to release
their seeds, by clearing away deadwood, and by encouraging new growth? Fire
14. How do humans affect the balance of carbon in the atmosphere? Burning fossil fuels in great
quantities has increased the amount of carbon dioxide in the atmosphere.
15. What is a photosynthetic organism and give an example. A photosynthetic organism is one that
uses the sunlight to create its own food/energy. An example is freshwater algae.
16. Define consumers. Organisms that eat other organisms and therefore, get solar or other energy
indirectly.
17. What are plants roles in the carbon cycle? They allow carbon to enter an ecosystem through
photosynthesis.
18. Why are bacteria that live within the roots of a soybean plant a critical part of the nitrogen
cycle? Because they change nitrogen in the atmosphere into a usable form.
19. Define secondary succession and give an example. Re-growth as a previously existing
community is replaced. EX: such as when new plants grow after a forest fire
20. What kinds of organisms are at the bottom trophic level of a food chain? Algae, grass
21. What term is used to refer to the many feeding relationships that are possible in an ecosystem?
Food Web
22. What is the role of nitrogen-fixing bacteria? It is responsible for making nitrogen in the
atmosphere usable by living organisms
23. What is a carbon sink? carbon in the atmosphere in the form of carbon dioxide and carbon
found within limestone rocks
24. What type of vegetation would you find in an area that has not been disturbed for 150 years?
Tall, mature oak trees
25. What is one of the largest carbon reservoirs on Earth? Limestone
26. Define autotrophs and give an example. Organisms that make their own food, EX: Trees
27. Define heterotrophs and give an example. Organisms that cannot make their own food and
must obtain energy from the foods they eat, EX: Humans
28. What is the equation for cellular respiration?
29. How does cellular respiration release energy? By breaking down food molecules
30. Give an example of a producer and a consumer in the same food chain. A zebra eating grass
31. What is found at each level of an ecological (energy) pyramid (beginning at the bottom)?
Producer, primary consumer, secondary consumer, tertiary consumer
32. How much energy is available to the organisms in each level of the energy (ecological) pyramid?
Ten percent of the energy available in the level below.
33. Define succession. The regular progression of species replacement in an environment.
34. What begins a food web? A producer (such as algae)
35. Define a food chain. The series of organisms showing a single feeding relationship in an
ecosystem.
36. Define a food web. Multiple food chains together showing all the possible feeding relationships
in an ecosystem.
37. Be able to follow a food web diagram.
38. At what trophic level are animals that feed on plants? 2nd trophic level (primary consumers)
39. What limits the number of trophic levels in an ecological pyramid? the amount of energy that is
lost at each trophic level
40. How does the number of organisms change as you move from one trophic level to the next?
As you move up the pyramid, the number of organisms decreases so the amount of usable
energy decreases.
41. Define biogeochemical cycle. Water and minerals needed by all organisms on Earth pass back
and forth between the biotic and abiotic portions of the environment.
42. List the components of the water cycle and define each.
Precipitation- rain, snow, sleet, or hail that falls to the ground
Evaporation-to change to vapor
Condensation- the conversion of a vapor or gas to a liquid
43. What happens in the nitrogen cycle? conversion of atmospheric nitrogen into usable organic
compounds by bacteria and conversion of nitrogen from decaying organisms into ammonia
44. What is common to the carbon cycle, the nitrogen cycle, and the water cycle? The substance
converted in each cycle is required by all living things and is involved in many processes that
occur in all living things.
45. List 2 things you know about coal, oil and natural gas. 1) they release carbon dioxide when they
are burned 2) they are fossil fuels
46. What percentage of energy is lost between trophic levels? 90%
47. What is the ultimate source of energy for the food (energy) pyramid? Sunlight
48. Photosynthesis uses sunlight to convert water and carbon dioxide into what? oxygen and highenergy sugars
49. What is found on the roots of plants that fix Nitrogen so the plant can use it? Bacteria
50. On an energy pyramid, which level has the smallest number of organisms? The top