Energy Flow and Cycles of Matter

Chapter 53

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

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

Ecological pyramids

Used to compare trophic levels Types:

Pyramid of numbersPyramid of biomassPyramid 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 plantsAvailable solar radiation, nutrients, waterMaturity of the communityHuman impacts

See table 53-1 p. 1049

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.

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

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 a form

that can be used: 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

Water (hydrologic) cycle

Necessary for life:Provides a medium for chemical reactions,

transports material throughout bodies, and moderates temperatures

Important processes:PrecipitationEvaporation, transpiration