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Chapter 3 Study Guide
1. How do primary producers make their own food? Be specific!
Absorb sunlight, water from the ground, and carbon dioxide from the atmosphere to
make glucose (carbohydrates) and give off oxygen
2. How are all heterotrophs alike?
All must consume (eat) something for food – can’t make their own food
3. List and describe the three types of ecological pyramids.
Energy – measures percentage of energy at each trophic level
Biomass – measures amount (grams) of organic matter at each trophic level
Numbers – measures the number of individuals at each trophic level
4. How can matter recycle through an ecosystem?
Through the biogeochemical cycles (water, nitrogen, carbon, & phosphorus)
5. What is primarily responsible for carrying out nitrogen fixation?
Bacteria on the roots of certain plants (legumes)
6. Why do organisms need nutrients?
To carry out their everyday functions
7. How are the movement of energy and the movement of nutrients different from
one another?
Energy moves in one direction only (producer through consumers)
Matter recycles over and over through the biogeochemical cycles
8. What is the purpose of biogeochemical cycling?
To move nutrients through the biosphere (living & nonliving parts) so they can be used
over and over again
9. Why don’t some producers make an unlimited supply of organic material?
Some nutrients are in short supply
10. Why is phosphorus so important?
Makes up an important part of DNA and RNA
11. What classification of organism is at the base of all ecological pyramids?
Primary producers (autotrophs)
12. What happens to the amount of energy available to an organism as you move
upwards in an ecological pyramid?
Decreases
13. How much energy is available from one trophic level to the next? 10%
14. Name and briefly describe the 4 biogeochemical cycles.
Water cycle: water moves between the ocean, atmosphere, & land; evaporation is how
water changes from liquid to gas; transpiration is how water evaporates from the
leaves of plants
Carbon cycle: carbon is a key ingredient of all organic compounds; processes involved
in the carbon cycle include photosynthesis and human activities such as burning
Nitrogen cycle: nitrogen is needed by all organisms to make proteins; nitrogen
fixation is how certain bacteria on plant roots convert nitrogen gas from the
atmosphere into ammonia; denitrification is how soil bacteria convert nitrates back
into nitrogen gas
Phosphorus cycle: phosphorus is needed for molecules such as DNA and RNA; is
stored in rocks and ocean sediments which is then slowly released into water and soil
15. What is the ultimate source of energy for everything here on Earth? sun