Notes 2.2: Energy Flow PAGES 366-369

Energy Flow in an EcosystemSun autotrophs heterotrophs

producers consumers

Producers/Autotrophs•Can make their own food through photosynthesis or chemosynthesis

Productivity•Productivity: energy made by producers (after biological processes) available to consumers

•Gross primary productivity (GPP): rate at which producers capture energy in organic compounds

Productivity•Net primary productivity (NPP): the rate at which biomass accumulates (after some is used)•NPP= GPP – Cellular Respiration• Cellular Respiration = making energy for the plant’s survival

Productivity•Biomass: the amount of organic (living) material produced

Consumers•Get energy by eating other organisms

•There are 5 types

Consumers

•Herbivores: eat producers

Consumers•Carnivores: eat other consumers

Consumers•Omnivores: eat producers and consumers

Consumers•Detritivores: feed on “garbage” or dead organic matter (ex. worms, millipedes, vultures)

Consumers•Decomposer: break down dead organic matter into simpler molecules (fungi and bacteria)•Recycle nutrients back into ecosystem

Food Chain•Food chain: a single pathway of feeding relationships in an ecosystem that traces the transfer of energy

Food Web•Interconnected food chains

•Arrows show transfer of energy

Trophic Level•Trophic level: position in a series of energy transfers

Energy flows through ecosystems

sun

producers (plants)

loss of

energy

loss of

energy

secondary

consumers

(carnivores)

primary consumers

(herbivores)

Trophic Levels•Only 10% of the total energy is passed onto the next trophic level (rule of 10%)

◦Energy lost to biological processes (digestion, growth and repair, running, walking etc.)

◦Energy lost as heat

• 3˚ Consumer

• Ex: killer whaleLarge

Carnivore

• 2˚Consumer

• Ex: sea otterSmall

Carnivore

• 1˚ Consumer

• Ex: sea urchin

Herbivore

• Ex: Kelp

Producer

90 % Energy

Lost

90 % Energy

Lost

90 % Energy

Lost

Question: Why is a pyramid used to display energy transfer and not a square?

Approximately 90% loss of energy at each trophic level

Keystone Species•Has disproportionately large effect on the ecosystem

•Dictates community structure

•Demonstrated by removal of keystone species from community•Ex. Sea stars, otters

Sea star feeds on all

bivalves. When the

sea star is removed

from the tide pools

one bivalve (mussel)

out competes the rest

for resources and

becomes the dominant

species.