Energy Flow, Food Chains and Food Webs

Ecology: study of interactions of organisms with each other and their environmentCommunity: all living things in a habitatPopulation: all the living organisms of one species in a habitatHabitat: where an organism livesEcosystem: 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 SunConsumers- organisms that get their energy by feeding on other organismsPrimary Consumers- animals that eat plants or parts of plants (fruit)- herbivoresSecondary Consumers- eat other animals- carnivores/predatorsTertiary Consumers- animals that eat secondary consumers- carnivores/predators- animals eaten and hunted by predators are called preyHerbivores- animals that get their energy by eating plantsCarnivores get their energy by eating other animalsOmnivores eat both plants and animalsDifferent stages of a food chain = trophic (meaning = feeding) levelsProducers = first trophic levelMost food chains are not very longanimal that feeds on tertiary consumers = quaternary consumerEventually 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 weedSome of the weed will not be digested and will pass out unusedOf the energy the tadpoles ingest, they will only use a small proportion for growthRest of the energy will be used by the tadpole in its life processes (movement, digestion etc.) or lost as heatAt each trophic level a large amount of energy is lost to the system = why food chains rarely have more than four stepsShort 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