There are so many species of organisms we need to have some means of grouping them.
In about  1750  Carolus Linnaeus, a Swedish naturalist, devised a system of grouping organisms into  categories based on characteristics, such as shape or structure.

Putting animals into groups is called classification

The major classification levels
from largest group to smallest

Kingdom – Phylum -Class – Order – Family – Genus- Species

All living things are divided into five kingdoms

There are 5 major kingdoms:

  • Bacteria
  • Single celled animals
  • Fungi
  • Plants
  • Animals


Each kingdom is sub-divided into smaller groups.
Two of these groups are the vertebrates (animals with a backbone)
and the Arthropods (animals with jointed legs and a hard outside skin called an exoskeleton)


Animals that have an internal skeleton

These animals all have a backbone


Main features or characteristics





Have hair or fur on their body
Babies are born alive and are fed with milk by their mother.
Breath with lungs
Warm Blooded

Dog, Mouse, Whale, Human


Have feathers
Lay eggs with hard shells
Breath with lungs
Warm Blooded

Robin, Crow


Skin covered in scales.
Lay soft-shelled eggs on land
Breath with lungs
Cold blooded

Lizard, Turtle,  Tortoise



Have a  smooth skin.
The young are born with gills and live underwater but the adults have lungs
and often live on land.
They lay jelly-covered eggs under water.   Cold blooded                                   

Toad, Newt



Have fins and scales
Lay eggs in water
Breath with gills
Cold  blooded                            

Shark, Cod



Animals  that have no backbone



 These animals all have jointed legs and an exoskeleton

(An exoskeleton is a hard, outside skin)





3 pairs
of legs, 3 parts to their body, hard outside skin

Fly, Butterfly, Ladybird, Ant


4 pairs
of legs and 2 parts to their body

Spider, Scorpion


More than 8 legs but less than
20. Often have a very hard, jointed skin

Crab, Lobster, shrimp


Other invertebrates



 Have a soft body and a muscular
foot. Sometimes they have a hard shell.
 Slug, Snail, Octopus



 Have a long, thin body which is
divided into little segments.
 Earthworm, Leach


*A warm blooded animal keeps its body at a constant temperature
eg humans have a body temperature of 37 C
A cold blooded animal has a body whose temperature varies according to the conditions.
eg The temperature of a fish would be slightly above that of the surrounding water (more if it had just been swimming rapidly)
Only birds and mammals are warm-blooded. all other animals are cold-blooded

Structure of an insect

An insect has 6 legs, three parts to its body and often 2 pairs of wings.
The three parts of an insects body are head, thorax and abdomen.
The hard outside skin of an insect protects the internal organs and is called an exoskeleton


A species is on of the groups within the classification system

Living things of the same type belong to the same species.
eg Humans are one species and cats are another and they look quite different
Animals from different species cannot usually reproduce together

Variation within a species

All animals of the same species will be similar but not identical.
For example all people belong to the species we call human but have differences such as skin colour, height and blood group.
These differences are known as variation
Variation within a species will be less than variation between species.

There are two kinds of variation

Continuous variation
These are differences that vary over a wide range such as height, weight or leaf size in plants.
Graph to show the height of children in the school
Which height range contained the most children children?Answer


Discontinuous variation
These are differences that have to have certain values such as
gender (male or female) or blood group (A, B, AB or O).

These values do not change over time

In plants an example  is the number of spikes on a holly leaf

Environmental and inherited causes of variation
Environmental variation is caused by the environment (soil type, climate, diet or by upbringing).
Examples of environmental variation are religion, language or plant growth

Inherited variation comes from the DNA of your parents.
Examples of inherited variation include things like eye colour, gender or blood type.
You will look similar to your mother and  father but not identical to either.
This is because each egg cell and sperm cell contain half the genetic information. These join at fertilization and provides all the genetic information needed,


The Plant Kingdom

Flowering plants: produce SEEDS. Eg grass, apple, oak, rose

All other plants are NON-FLOWERING and do NOT produce seeds. Eg algae, moss and fungi.

The kingdom of Fungi
Fungi are not true plants as they do not possess green chlorophyll so cannot carry out photosynthesis.

They take their food from the material they are growing on/in.
Reproduce asexually by making spores.
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.



Words to know from this section
VERTEBRATE      Has an internal skeleton

INVERTEBRATE   Has no internal skeleton

EXOSKELETON   An external skeleton, like a hard skin.

WARM-BLOODED   Animals whose body temperature is constant are called warm-blooded. eg Human: body temperature 37oC.

COLD-BLOODED   Animals whose body temperature alters with the temperature of the surroundings eg fish