Chapter 54 Reading Quiz

1. Chapter 54 Reading Quiz • Which trophic level ultimately supports all of the others? • What 2 things limit primary productivity in aquatic ecosystems? • Which biogeochemical cycle includes evaporation & precipitation? • Which biogeochemical cycle includes photosynthesis & cellular respiration?

2. 1. Distinguish between trophic structure and trophic levels. • Trophic structure  the feeding relationships in an ecosystem that determine the paths of energy flow and chemical cycling • Trophic levels  ecologists divide the species in a community or ecosystem into different trophic levels based on their main source of nutrition 

3. 2. Overview primary consumers and producers. How are these different from secondary consumers? Tertiary consumers? List examples. • Primary producers  autotrophs that support all other trophic levels either directly or indirectly by making sugars • Primary consumers  herbivores that consume primary producers • Secondary consumers  carnivores that eat the herbivores • Tertiary consumers  carnivores that eat the other carnivores 

5. 3. What are detritivores? What do they eat? • Detritivores  (decomposers) consumers that derive energy from detritus (organic waste) and dead organisms from other trophic levels • These form a major link between primary producers and the consumers in the ecosystem 

6. 4. Differentiate between a food chain and a food web. How does production differ from consumption differ from decomposition? • Food chain  the pathway along which food is transferred from trophic level to trophic level, beginning with primary producers • Food web  the elaborate feeding relationships between the species in an ecosystem • Production  the rate of incorporation of energy and materials into the bodies of organisms • Consumption  refers to the metabolic use of assimilated organic molecules for organismal growth and reproduction • Decomposition  the breakdown of organic molecules into inorganic molecules 

7. 5. Overview how energy flows through an ecosystem. • Energy for growth, maintenance, and reproduction is required by all organisms • The ecosystem’s budget relies on primary productivity • Light  Plants  Animals  Bacteria/Fungi 

8. 6. Distinguish between gross primary productivity and net primary productivity. • Gross primary productivity  the total amount of light energy converted to chemical energy by autotrophs of an ecosystem (measured by the oxygen produced) • Net primary productivity  is the GPP minus the energy used by producers for respiration - the organic mass available to consumers 

10. 7. What is biomass? What is a limiting nutrient? • Biomass  how primary productivity is expressed as amount added to an ecosystem per unit area per unit time (g/m2/yr) or energy (J/m2/yr) • Limiting nutrient  when a nutrient has been removed in such quantities that sufficient amounts are no longer available 

12. 8. Overview the ecological pyramids. • The transfer of energy from one trophic level to the next is not 100% • Energy flows through an ecosystem, it does not cycle • The pyramids can symbolize: 1. Productivity in the trophic levels 2. Biomass 3. Numbers of individuals 

15. 9. List the biogeochemical cycles. Why is it necessary for nutrients to cycle? • Biogeochemical cycles  nutrient circuits involving both biotic and abiotic components of ecosystems • Water • Carbon • Nitrogen • Phosphorus • Necessary for life to continue 

17. 10. Overview the water cycle, the carbon cycle, the nitrogen cycle, and the phosphorus cycle. • Water  evaporation, precipitation • Carbon  photosynthesis, cellular respiration • Nitrogen  needed for amino acids, nitrogen is fixed, plants take it up, animals eat the plants, death and waste enter soil, bacteria nitrify it back to the atmosphere • Phosphorus  needed for nucleic acids, membranes, ATP, short and long term cycles 

23. 11. Describe what happens in decomposition. • The rate of decomposition has a great impact on the timetable for nutrient cycling • In tropical rain forests: months to years • In temperate forests: 4 – 6 years • In the tundra: over 50 years • Soil chemistry and fire frequency influence 

24. 12. How does vegetation regulate chemical cycling? • Plants retain nutrients within an ecosystem • If logging and deforestation occur, less nutrients are retained in that area 

25. 13. How are human populations disrupting chemical cycles? • Often humans remove nutrients from one part of the biosphere and add them to another • Farming exhausts nutrients in an area, and then causes runoff of fertilizers and waste • From this, disruptions can flow from one ecosystem to another 

27. 14. Describe the concept of “biological magnification”. • Biological magnification  the process by which toxins become more concentrated with each successive trophic level of a food web; results from biomass at each trophic level being produced from a much larger biomass ingested from the level below • Ex: mercury and tuna fishing 

29. 15. Describe how humans are causing changes in the atmosphere. • Carbon dioxide emissions and the greenhouse effect - CO2 doesn’t escape the earth • Depletion of atmospheric ozone - O3 is broken apart and does not provide the protection from UV rays 