Ecosystem Ecology Chapter 3

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

Energy flow in ecosystems ONE WAY! Laws of thermodynamics always apply: 1. Energy cannot be created or destroyed, only converted from 1 form to another 2. 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

Ecological pyramids Used to compare trophic levels Types:  Pyramid of numbers  Pyramid of biomass  Pyramid of energy

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

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

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

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.

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

Carbon cycle C is in organic compounds: proteins, nucleic acids, lipids, carbohydrates CO 2 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 CO 2 in atmosphere

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

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