1. Ecosystem Ecology
Chapter 3

2. You should know: 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: See table 3.8 p. 64
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