Ecosystem Ecology

1. Ecosystem Ecology Chapter 3

2. Terms to remember… • Ecosystem • Biotic/abiotic • Producer/autotroph • Consumer/heterotroph • Photosynthesis/cellular respiration • Trophic levels • Primary consumer/secondary consumer/tertiary consumer • Food chain/food web • Herbivore/carnivore/omnivore • Scavenger/detritivore/decomposer

3. Energy flow in ecosystems • ONE WAY! • Laws of thermodynamics always apply: • Energy cannot be created or destroyed, only converted from 1 form to another • Whenever energy is converted from 1 form to another, some of the energy is lost as heat • Simplified version: food chain • Detailed version: food web • Energy input  autotroph  heterotroph • Note that the  shows the direction of energy flow

4. Ecological pyramids • Used to compare trophic levels • Types: • Pyramid of numbers • Pyramid of biomass • Pyramid of energy

6. Ecosystem productivity • GPP = gross (total) energy captured during photosynthesis • Plants use some of this energy during cellular respiration • NPP = net (remaining) energy • NPP = GPP – plant respiration

8. Productivity… • Influenced by lots of factors: • Type of plants • Available solar radiation, nutrients, water • Maturity of the community • Human impacts • See table 3.8 p. 64

11. Bioaccumulation • As substances move through a food chain, some are not passed on • These substances can be stored in the bodies of organisms in the food chain – bioaccumulation • Fat-soluble toxins tend to build up in higher levels of a food chain – biological magnification • Example – DDT pesticide and Bald Eagle

12. Biogeochemical cycles • Not one way! • Earth is a closed system – matter cannot escape • Law of conservation of matter: • Matter cannot be created or destroyed, it can only be changed from one form to another.

13. Water (hydrologic) cycle • Necessary for life: • Provides a medium for chemical reactions, transports material throughout bodies, and moderates temperatures • Important processes: • Precipitation • Evaporation, transpiration • Runoff

14. Carbon cycle • C is in organic compounds: proteins, nucleic acids, lipids, carbohydrates • CO2 is stored in the atmosphere (and in some rocks) • Important processes: • Photosynthesis • Respiration, decomposition, combustion • Human impact on carbon cycle – increased combustion has increased amount of CO2 in atmosphere

15. Nitrogen cycle • N is found in proteins, nucleic acids, and chlorophyll • 78% of atmosphere is N, but this is not in a form that can be absorbed by living things • Nitrogen fixation – converts atmospheric N into nitrates and nitrites - forms that can be used by plants: combustion, volcanic action, lightning, and nitrogen-fixing bacteria • Nitrogen-fixing bacteria – live in nodules on the roots of plants called legumes • Nitrogen is returned to the atmosphere during decomposition

16. Phosphorus cycle • P is found in nucleic acids, ATP and phospholipids found in cell membranes • P is not found as a gas in the atmosphere • It cycles from the soil, into the food chain and back • Phosphorus is a limiting factor in many aquatic ecosystems • Sudden input into an ecosystem can cause rapid growth of algae – algal bloom • When algae begins to die and decompose, the oxygen in the system is consumed, resulting in hypoxic conditions