Food chain    Food web    Importance of fungi    Balance of nature    Adaption

ECOLOGY Is the study of animals and plants in their Natural environment

In any habitat there will be a community of animals and plants.

The habitat, the animals and plants in the habitat and the physical environment make up an ecosystem

The habitat of an animal needs to provide a place to make its home and breed, the correct food, shelter from the weather and protection from its enemies.

Plants can make food from simple chemicals around them, (carbon dioxide from the air, water containing dissolved minerals from the soil). using a process called photosynthesis
The energy to do this comes from the sun.

Animals rely on plants or other animals for their food.

Without plants all life on this planet would die.

A food chain list of organisms to show a simple feeding pattern within a habitat

eg    CABBAGE  →  SLUG  →  THRUSH  →  CAT

This means that the cabbage is eaten by the slug ….
which is eaten by the thrush.
.. which is eaten by the cat

The arrows shows the transfer of food energy from one organism to the next.
The cabbage leaf gets its energy from the sun.

The first organism in a food chain is called a PRODUCER and is always a PLANT

All other organisms in the food chain are CONSUMERS 

The animal at the top of the food chain is often a PREDATOR and is called a top carnivore


The animals which eat the plant are called HERBIVORES
The animals which eat other animals are called CARNIVORES

Most animals and plants will belong to more than one food chain.
(eg a lettuce can be eaten by slugs or greenfly)
A food web is a diagram that shows several food chains from the same habitat.
Garden food web
Decomposers (small animals that live in the soil, worms, beetles etc) help recycle the dead food and so provide simple chemicals (mostly nitrates) for the plants to use again. A vital part of this recycling are the SAPROPHYTES (fungi and bacteria)

The Importance of Bacteria and Fungi
Fungi and bacteria are known as saprophytes.
Saprophytes are DECAY ORGANISMS and are responsible for getting dead animals and plants to rot (decompose).
They break down the remains into simple chemicals eg nitrates which contain nitrogen, an important element needed by plants.
Without saprophytes the soil would quickly run out of nutrients and the plants would have no food.

The balance of nature
Life in any ecosystem is in a delicate balance.
Changing one organism in a food web can alter that balance.

Three examples (A,B, and C)
If an insecticide  (insect killer) was sprayed on to a garden what might happen?      (look at the food web above)

  • The greenfly (an insect) would all die
  • This would make the ladybird population go down and the roses would not get eaten
  • The thrush would have less food so would have to eat more slugs
  • This would mean that there would be more lettuces.

If the slugs had got killed as well by the insecticide there would have been be a different effect.

B. Imagine the effect of introducing a pike (or other predator) into a village pond.

  • All the small fish would get eaten.
  • The pike would then have no food so it would also die
  • The number of plants in the pond would increase because there would be nothing eating them.

C: In some country areas they used to cut down the hedges to make the fields larger so make it easier to harvest the crops.

This had a disastrous effect:
By moving the hedges they destroyed the habitat of small birds (thrushes etc).
The birds moved away so there was nothing to eat the insects.
The insects, now with a much larger population, caused a lot of damage to the crops.
The farmers would have been better off leaving things as they were.

Limiting Factors:
A limiting factor is something that prevents a population from getting any larger.
eg food
If there was a field full of rabbits they would breed rapidly and so eat more grass.
As the grass starts to run out a lot of rabbits will die (or move away). The amount of grass will now start to increase again  and so will the number of rabbits. The number of rabbits and amount of grass will continue to cycle up and down.

Adding a fox to the field will alter the balance.

Typical limiting factors are:


  • Space
  • Build up of waste


Animals and plants are adapted to their habitats. This means that they have evolved special features that help them to survive.
An African elephant, for example, lives in a hot habitat and has very large ears that it flaps to keep cool. A polar bear, on the other hand, lives in a cold habitat and has thick fur to keep warm.


A green tree frog

Different varieties of frogs have different adaptions but in general:

  • Large eyes help it see in low light conditions (like in an owl)
    The eyes are on the top of its head so it can remain mostly underwater to keep it hidden.
  • The special damp skin of a frog allows oxygen to pass through it. This means it can stay underwater for long periods of time (again to hunt for food or escape danger)
  • A sticky tongue helps it catch insects
  • The powerful hind legs help it jump (to escape from danger)
  • The webbed feet help it swim
  • This particular frog has pads on its feet to help it climb



Words to know

ADAPTION: Most animals and plants have evolved special features to help them survive in their environment. We call these changes ‘adaption’

ENVIRONMENT The external surroundings that an animal or plant lives in and which influence its life or development. The environment can be effected by physical factors such as soil temperature, humidity, air temperature, moisture content of soil, pH, light intensity and nutrients in the soil..

HABITAT The place where an animal or plant makes its home
eg woodland, fresh-water stream, desert.

POPULATION A group of animals or plants of the same species living in a particular area.

COMMUNITY A collection of all the animals and plants that live in a particular area.

ECOSYSTEM A community of animals and plants and the habitat where they live.

HERBIVORE An animal that eats only plants
(herbivorous) (leaves, seeds, berries, bark etc) eg snail, mouse

CARNIVORE An animal that eats only meat.
(carnivorous) eg thrush, pike, ladybird

OMNIVORE An animal that eats plants and meat.
(omnivorous) eg rat, human

PREDATOR An animal that hunts for food. eg hawk, pike.

PARASITE An animal or plant that lives on (or inside) the body of another living organism eg leech, flea, tapeworm

HOST The organism on which a parasite is living
eg if a flea lives on a fox then the fox is the host and the flea the parasite.

SCAVENGER An animal that lives from the remains of other animals.
eg shrimp, various beetles.

DECOMPOSER An animal that lives on the rotting remains of other organisms. Decomposers help in the recycling of dead material returning essential nutrients to the ground.
eg fungi, bacteria, various beetles, worms

SAPROPHYTE A decay organism. Saprophytes cause the remains of organisms to rot. They are vital for the recycling of nutrients into the ground. eg fungi and bacteria.

PRODUCER The first organism in a food chain. Always a green plant. Green plants are the only organisms that can carry out photosynthesis and produce their own food from simple chemicals in the soil and air. Note: fungi do not possess chlorophyll and so are NOT considered as producers

CONSUMER All the animals in a food chain. Animals rely on other animals or plants for their food as they cannot produce their own.

PRIMARY CONSUMER The first consumer in a food chain. Always a herbivore.

TOP CARNIVORE The carnivore at the end of a food chain. eg fox, pike.

FOOD WEB A diagram that represents several interlinked food chains

FLOWERING PLANTS Plants that produce SEEDS. Eg grass, apple, oak, rose

NON-FLOWERING PLANTS Plants that do NOT produce seeds. Eg algae, moss and fungi.

Algae Single celled plants. Reproduce asexually by binary fission. Live in wet places. Have no leaves or roots.

Moss Reproduces asexually by making spores. Live in damp, shady places.

Fungi Reproduces asexually by making spores. Does not possess green chlorophyll so cannot carry out photosynthesis.

They take their food from the material they are growing on/in.

Examples of different fungi: mushroom, yeast, mould.

Fungi (along with bacteria) are very important in the food chain for the recycling of nutrients in the soil.

Some fungi are harmful and can cause disease in crops (eg potato blight).

Some fungi are useful to man eg yeast which is used to ferment sugar and produce alcohol in the brewing industry.

The DOMINANT plant is the one that has the most effect on the habitat.


QUADRAT A rectangle of known area (eg 1m2) used for estimating the population size of an organism.

POOTER A device for sucking up small organisms.

TULLGREN FUNNEL A device used for sampling small invertebrates found in leaf litter.

The different animals and plants in a habitat can be identified using a key