1. energy flow

Environmental Biology & Genetics

Energy Flow

Mr G Davidson

Mr G Davidson

Thursday, April 13, 2023Thursday, April 13, 2023 22Mr G DavidsonMr G Davidson

Ecosystems

An ecosystem is a natural unit composed of living organisms and their non-living environment, e.g. a woodland.

A habitat is the place where an organism lives, e.g. greenfly live on the leaves of the trees.

An organism’s niche is the role it plays within the ecosystem e.g a tawny owl is top predator in a woodland.


Ecosystems


Ecosystems

A population is the total number of organisms of one species living in a habitat, e.g. the total number of greenfly in the woodland.

A community is made up of all the living organisms in a habitat, e.g. all the trees, grass, insects, birds, etc..


Ecosystems


Ecosystems

A species is a group of organisms which can interbreed to produce fertile offspring.

Donkey Horse

Mule

Horses and donkeys can mate to produce a mule – but mules are not fertile so horses

and donkeys are separate species

Ecosystems

All of the energy required by all living organisms in an ecosystem comes from the sun.

Light energy from the sun is converted to chemical energy by plants in a process called photosynthesis.



Producers & Consumers

Producers are organisms which can produce their own food by photosynthesis – usually green plants.

Consumers are animals which consume (eat) other organisms. They cannot make their own food.



A primary consumer is an animal which eats plants, and is also known as a herbivore.

A secondary consumer is an animal which eats primary consumers, and is also known as a carnivore.



An omnivore can eat both plants and animals.

Decomposers are bacteria and fungi which break down dead plants and animals for energy and release their nutrients back into the ecosystem.



An animal which hunts other animals for food is called a predator.

An animal which is hunted by other animals as food is called prey.


Food Chains & Webs

A FOOD CHAIN shows a feeding relationship. It is usually written as:

Green plant herbivorecarnivore

The arrows in a food chain point from food to feeder and show the direction of energy flow.

A food chain always starts with a producer (green plant).


Food Chains & Webs

Energy is transferred in the form of chemical energy in food from plants to animals and then to other animals.

A green plant (producer) can be eaten by a herbivore.

The herbivore in turn can be eaten by a carnivore.

Food Chains and Food Webs


Green Plant

PRODUCER

Rabbit

PRIMARY CONSUMER

(HERBIVORE)

Fox

SECONDARY CONSUMER

(CARNIVORE)

ENERGY ENERGY


Food Chains & Webs

Feeding relationships are more complicated than food chains suggest.

Food chains interconnect at many points.

This interconnection of food chains is called a food web.


Food Chains & Webs

FOX

SNAIL

HEDGEHOG

WEASEL

FROG

VOLE

PRIMROSE PLANT

OWL

RABBIT

OAK


Energy Flow and Loss

Every time one organism eats another, energy is transferred from the food to the feeder.

The arrow indicates the direction of energy flow.

E.g.Oak leaf Caterpillar ShrewBadger


Energy Flow and Loss

Not all the energy available at each step in a food chain is passed onto the next step.

Only about 10% is passed on.90% of the energy is lost e.g. as:

MovementHeat productionWaste.


Pyramid of Numbers

A pyramid of numbers is a diagram which represents the number of organisms at each stage in a food chain.

A pyramid of numbers can look like:


Pyramid of Numbers

GrassGreenfly

Ladybird

ThrushNumber of organisms decrease

Size of organisms increase


Pyramid of Numbers

Grass

Greenfly

Ladybird

Thrush


Pyramids of Energy

A pyramid of energy is a diagram which represents the amount of energy available at each level of a food chain.

It is usually measured in kilojoules of dry mass per square metre per year.


Pyramid of Energy

100 000 kJ

10 000 kJ

1 000 kJ

100 kJ


Pyramid of Biomass

A pyramid of Biomass is a diagram which represents the total mass of organisms at each level of a food chain.


Pyramid of Biomass

Oak leaves

Caterpillars

Sparrows

The energy available to the caterpillars is less than the energy available to the sparrows, and

therefore, the caterpillars produce a greater biomass than the sparrows.

Vocabularyecosystem carnivorehabitat predatorniche preypopulation decomposercommunity species producer pyramid of numbers primary consumer pyramid of biomass secondary consumer pyramid of energy herbivore


1. energy flow

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