Energy transfer

Energy sources

The sun provides almost all the energy to sustain life. Producers use Photosynthesis or Chemosythesis

acquire the energy needed to live. Chemosythesis is the use of inorganic compound to

gain energy, only bacteria use this energy source.

Measuring productivity

Biomass is the amount of organic matter in an ecosystem Producers make biomass

Gross primary productivity is the rate at which producer use solar energy to make biomass and maintain the producers metabolism.

Net primary productivity is the amount of biomass left for consumers to eat. Productivity is measured in units of energy per unit area

per year.

Which biomes are the lest productive? Which are the most? Why do you think that is?

Consumers

primary consumers:Herbivores – eat producers

secondary consumers: Carnivores: meat eatersOmnivores: eat producers & consumers

• Detritivore: eat dead plants and animals & animal waste

• E.g. Voltures and dung beetles • decomposers are detritivors that

break down organic matter into nutrients

• e.g. bacteria and fungi

Energy flow

• Each level in the pyramid is called a trophic level.

• As levels increase energy is lost as heat or used for growth.

• Only 1/10th of the energy is available for the next level in the pyramid

Left side: Why do you think there is no quaternary level? Does it take more land to feed a vegetarian or an omnivore? With a growing human population (7 billion +) what is the best way to use our arable land resources?

Energy use in a trophic pyramid

o Only 10% of energy is available from one trophic level to the next.

o There is a limit to the number of trophic levels there can be.

Food chains & webs Food chain – a single

pathway fro energy to move through the tropic levels.

Food web - Several food chains linked together

Shows how energy moves through a community

A change to one part of the web affects all the others Fresh water food web: Arrows mean “eaten by”

A forest food web

Antarctic marine food web is supported by krill, a small crustacean

Krill feed on algae & other protozoans

Summary review 1. What happens to a community if the number or output of the producers is

lowered, say in a drought?2. What would happen if the decomposers died?3. What happens if the top predators are killed by humans?4. How are food chains and webs different? Which is the more accurate way

to show how energy moves through a community?