8B1 Ecology & Environment
Variation and classification
Variation
A species is a group of organisms that can reproduce with one another to produce offspring that will
also be able to reproduce. The differences between organisms are known as variation. There is
variation between different species and between members of the same species.
There is variation between different species. Lions
and tigers are different species. Tigers have stripes, lions
do not.
There is variation between members of the same species.
All tigers have different patterns of stripes.
Sometimes there is a relationship or correlation between two features. A relationship is normally
best shown on a line graph. The line will go steadily up or steadily down.
Variation can have environmental or inherited causes.
Relationship: people with longer arms have longer middle fingers.
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Environmental variation
An organism’s surroundings are known as its environment. The conditions in an environment are
called environmental factors. Plants are affected by environmental factors like the amount of light,
the amount of water, the amount of warmth and the amount of mineral salts in the soil.
The cress seedlings on the left have not had enough light.
The plant on the left has not had enough water. It has
wilted.
Animals are also affected by environmental factors. Humans who get sunburnt or have scars are
examples.
Inherited variation
This is caused by features being passed from parents to their offspring.
In humans, natural eye colour and natural hair colour are both examples of inherited variation.
Classification
There are so many species that we need to put them into groups. This is called classification.
The first set of groups that organisms are divided into are called kingdoms. The two largest
kingdoms are the plant kingdom and the animal kingdom. The main difference between these two
kingdoms is that plants can make their own food and animals cannot.
The animal kingdom is divided into other groups. The vertebrates are animals that have a
backbone. There are five sorts of vertebrate. There are another eight groups which are all
invertebrates. The most important groups to know about are in bold type.
Adapted from Exploring Science for QCA Copymaster File 7
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The plant kingdom is also divided into groups.
Habitats
A habitat is the area where an organism lives. The surroundings of an organism are called its
environment. The conditions in an environment are caused by physical environmental factors.
Examples include how light it is and what the temperature is. Smaller areas in a habitat are called
microhabitats.
Where you can find a certain organism in a habitat is known as the organism’s distribution. A
community is all the plants and animals in a habitat.
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Jack rabbits are adapted to living in a desert habitat.
Animals and plants are adapted to where they live. This means that they have certain features that
allow them to survive in a habitat. For example, fish are adapted to living under water. They have
gills to take oxygen out of the water, fins to swim with and streamlined bodies to help them move
easily through the water. Here is another example:
Physical environmental factors change from day to day (daily changes). Animals that only come
out at night are called nocturnal animals (e.g. an owl).
Physical environmental factors change over the year (seasonal changes). Organisms adapt to these
changes. When it starts to get colder, some birds migrate to warmer countries where there is more
food. There are other ways plants and animals cope. Look at the picture to discover some of these.
Organisms are in competition with each other. Animals compete for food and space. Plants
compete for light, water and nutrients (mineral salts).
Feeding relationships
An animal that hunts other animals is a predator. What it hunts is its prey. We can show what eats
what on a food chain. Different words are used to describe what the organisms do in a food chain.
producer
Adapted from Exploring Science for QCA Copymaster File 7
consumers
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herbivore
carnivore
prey for the robin
prey for the
sparrowhawk
carnivore
predator of the
caterpillar
predator of the
robin
top predator
grass 
caterpillar 
sparrowhawk
robin
Food chains are joined to form food webs. Food webs can also show omnivores (animals that eat
both plants and other animals).
Plants are producers because they can produce their own food. Energy from the Sun is used to help
them do this. This light energy is turned into chemical energy in the producer. When a consumer
eats a producer, the consumer gets the chemical energy.
Food chains and food webs show how energy flows through a community.
Animals that are predators have adaptations that allow them to catch their prey. Animals that are
prey have adaptations for avoiding being eaten!
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© Pearson Education Limited 2002
Many predators have...
Many prey have...
forward facing eyes to look out for prey.
eyes on the sides of their heads so that they can
keep a lookout behind them.
large, sharp claws.
some form of protection (e.g. horns, spines or
armour).
Often, animals have adaptations for eating, either in or on their mouths:
You can find evidence of what has been eating something by:
•
•
•
seeing it happen
finding animal droppings or footprints near a damaged plant or dead animal
finding teeth marks in a damaged plant or dead animal.
We can use this evidence to draw food chains and webs for habitats.
Ecological relationships
Habitats and environments
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© Pearson Education Limited 2002
A habitat is the area where an organism lives.
Non-living factors in a habitat are called physical
environmental factors. Examples include how
light it is and what the temperature is. These make
up the surroundings, or environment, of an
organism.
Small areas in a habitat are called microhabitats.
For example, the fur on a fox is a microhabitat.
All the plants and animals that live in a habitat make up a community. Within a community, the
total number of one species is called a population. There will be a population of foxes in a wood.
In order to survive in a habitat, organisms need various resources. An animal needs food, water,
oxygen, shelter and it needs to find a mate to reproduce. Plants need light, water and carbon dioxide
in order to make food. They also need mineral salts (nutrients), oxygen and space to grow.
Adaptations
In any habitat, the organisms living there must be adapted to survive the environmental conditions
within that habitat. Members of the same community may have similar adaptations to cope with
the problems of their habitat. For example, many small animals and plants which live in fastflowing rivers are adapted to stop them being swept away. In ponds, free-swimming animals and
floating plants can survive because there is no current to wash them away.
All the places in an environment where an organism is found
is called its distribution. For example, in a pond habitat pond
skaters are found on the surface of the water. They are
adapted to living here because they have bristles on the ends
of their legs, which prevent them from breaking the surface
film of water. They feed on dead insects floating on the water.
Organisms that are better adapted to survive in an area will
have a better chance of survival.
Adapted from Exploring Science for QCA Copymaster File 7
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Classifying living organisms
Each different type of organism is called a species. There are so many species that we need to put
them into groups. This is called classification. The largest groups are called kingdoms and the
biggest of these are the plant kingdom and the animal kingdom. The Summary Sheets for Unit 7D
Variation and classification show how animals are classified into groups.
The main difference between plants and animals is that plants can make their own food by
photosynthesis.
There are four main plant groups.
Sampling methods
Ecologists are scientists who study habitats. They catch organisms using various sampling
techniques, then use keys and field guides to identify them.
A pooter is used to collect small
invertebrates.
A Tullgren funnel is used to collect
invertebrates from leaf litter.
A pitfall trap traps small animals that
crawl along the ground.
Tree beating is used to collect
animals that live in trees or bushes.
Pond dipping is used to collect
organisms from different parts of a
pond.
A sweepnet is used to collect
organisms from long grass.
Ecologists often need to know the size of a population. It would be impossible to count all the
organisms in a habitat, so they take samples and then estimate the total number of organisms.
Adapted from Exploring Science for QCA Copymaster File 7
© Pearson Education Limited 2002
A quadrat is a sampling square used to estimate plant populations. The quadrat is placed randomly
on the ground in different parts of the habitat and the number of plants inside it is counted each
time.
The more samples that are taken, the more reliable an estimate will be.
Ecologists also measure the physical environmental factors, like how warm it is and how much
oxygen is dissolved in pond water, using sensors and dataloggers. They then look to see if there are
any links between the factors, such as, the warmer the water the lower the oxygen level is.
Feeding relationships
Food chains and food webs show the feeding relationships between different organisms in a
habitat. (See Summary Sheets for Unit 7C Environment and feeding relationships).
The numbers of organisms at each level in a food chain can be shown as a pyramid of numbers.
The size of the bars shows the number of organisms. Usually there are fewer organisms as you go
along a food chain because energy is lost at each level, for example, for movement. Sometimes the
pyramid has an unusual shape if the organisms are very different in size.
grass  caterpillar  robin  sparrowhawk
rose bush  aphids  ladybirds
Adapted from Exploring Science for QCA Copymaster File 7
© Pearson Education Limited 2002
Populations
The size of a population is affected by several factors.
•
Animals compete with each other for resources such as food, water and shelter.
•
Plants compete for light, water, nutrients (mineral salts) and space.
•
If there are not enough resources the population will decrease.
•
Disease can kill organisms.
•
The populations of predators and prey are linked. When there are a lot of prey organisms, the
number of predators increases because they have plenty of food.
This decreases the number of prey, which then leads to a decrease in the number of predators.
•
Harsh weather conditions can reduce populations.
Living organisms depend on others for their survival. For example, plants depend on insects for
pollination.
Adapted from Exploring Science for QCA Copymaster File 7
© Pearson Education Limited 2002