Chapter 54 Reading Quiz 1.Which trophic level ultimately supports all of the others? 2.What 2 things limit primary productivity in aquatic ecosystems? 3.Which biogeochemical cycle includes evaporation & precipitation? 4.Which biogeochemical cycle includes photosynthesis & cellular respiration?

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

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

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

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

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

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

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/m 2 /yr) or energy (J/m 2 /yr) Limiting nutrient  when a nutrient has been removed in such quantities that sufficient amounts are no longer available

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

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 1.Water 2.Carbon 3.Nitrogen 4.Phosphorus Necessary for life to continue

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

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

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 

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 

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

15. Describe how humans are causing changes in the atmosphere. Carbon dioxide emissions and the greenhouse effect - CO 2 doesn’t escape the earth Depletion of atmospheric ozone - O 3 is broken apart and does not provide the protection from UV rays 