Energy Flow, Food Chains and Food Webs

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Ecology: study of interactions of organisms with each other and their environment

Community: all living things in a habitat

Population: all the living organisms of one species in a habitat

Habitat: where an organism lives

Ecosystem: interacting group of organisms and their environment

Food chains:

- show how living things get their food

- show how they get their energy

(sometimes written to include the sun)

the Sun is the principal source of energy input to biological systems

- can be written going up or down a page or right to left

- arrows shows the direction of the flow of energy

- are charts showing the flow of energy from one organism to another

Stages:

Producers

- green plants

- make their own organic nutrients (usually by photosynthesis) using energy from the Sun

Consumers

- organisms that get their energy by feeding on other organisms

Primary Consumers

- animals that eat plants or parts of plants (fruit)

- herbivores

Secondary Consumers

- eat other animals

- carnivores/predators

Tertiary Consumers

- animals that eat secondary consumers

- carnivores/predators

- animals eaten and hunted by predators are called prey

Herbivores

- animals that get their energy by eating plants

Carnivores get their energy by eating other animals

Omnivores eat both plants and animals

Different stages of a food chain = trophic (meaning = feeding) levels

Producers = first trophic level

Most food chains are not very long

animal that feeds on tertiary consumers = quaternary consumer

Eventually all the organisms involved in the food chain will die and become food for decomposes: organisms such as bacteria and fungi that break down dead plants and animals or waste organic matter to get energy

The arrows in food chains and webs show transfer of energy

- not all energy that enters an animal or plant is available to the next trophic level

- only energy that has resulted in an organism's growth will be available to the animal that eats it

Some of the energy will be used for respiration, but some will be used for growth (therefore will be available to a future consumer)

Not all of the energy will be available to the tadpoles:

- some weed may be eaten by other animals

- tadpoles will not eat all of the weed

Some of the weed will not be digested and will pass out unused

Of the energy the tadpoles ingest, they will only use a small proportion for growth

Rest of the energy will be used by the tadpole in its life processes (movement, digestion etc.) or lost as heat

At each trophic level a large amount of energy is lost to the system = why food chains rarely have more than four steps

Short food chain = most efficient as there is more energy

Food Web: networks of interconnected food chains showing the energy flow through part of the ecosystem

- unusual to find a food chain not part of a larger food web

- help in showing how different animals feed

- help us see what might happen if the food web is disturbed in some way

If

If an animal is removed from a web the population of some animals becomes too high and causes the others to become too low

Introduction

Food Chains

Energy Flow

Food Webs