How to classify plants and animals

Classification is the process of organising living things into categories.

These categories help us to see how different organisms are related to each other.

The system scientists use to classify living things is called taxonomy.

Think of it like a library: Just like books are sorted into different genres like fiction, non-fiction and reference, living things are sorted into groups based on their similarities and differences.

• Vertebrates are animals with a backbone, like mammals and reptiles.

• Invertebrates are animals without a backbone, like crustaceans, molluscs and insects.

• Mammals breathe using lungs, whereas fish breathe underwater with gills.

• The largest animals in the main ecosystems are normally vertebrates, such as the blue whale.

• The largest invertebrate is the colossal squid, which can grow over 10 metres in length.

• Colossal squid were first discovered in 1925. They were not filmed in their natural habitat until 100 years later in 2025, by a team led by a scientist from the University of Essex.

• All mammals are warm-blooded.

• All animals originated from the sea before evolving to live in different habitats. We can see this from studying fossils.

Animals can be divided into two groups:

1. Vertebrates – animals with a backbone, such as fish, reptiles and mammals.
2. Invertebrates – animals without a backbone, such as insects, molluscs and crustaceans.

Vertebrates can be then classified into five main groups:

• Amphibians
• Birds
• Fish
• Mammals
• Reptiles

Most of the world's animal species are invertebrates, so there are lots of different ways to group them.

Some of the groups that animals are classified into are:

• annelids – segmented worms such as earthworms, ragworms and leeches
• arachnids – a family of animals that includes spiders, scorpions, ticks and mites
• crustaceans – examples of crustaceans include shrimps, crabs, woodlice and lobsters
• insects – including ants, beetles, and butterflies
• molluscs – like slugs, snails, octopuses and oysters

Did you know?

A fossil is the preserved remains or traces of a dead organism and they are usually found in rocks.

Fossils can provide scientists with evidence of extinct species, and also show how a species has evolved over millions of years.

Did you know?

Fossil records of sharks have been discovered dating back over 400 million years, meaning that sharks were alive at the same time as the dinosaurs.

There are more than 500 classified species of shark which currently live in the Earth's seas and oceans.

Plants are classified into two main groups:

1. Plants that make seeds.
2. Plants that don't make seeds.

These two groups can be split into many smaller ones. Plants that make seeds are either flowering plants or conifer trees.

Examples of plants that don't make seeds include ferns or mosses, which instead produce spores.

Did you know?

The Svalbard Global Seed Vault is the world's largest seed bank. It has seeds in storage from millions of plant species, and some extinct ones too.

The vault is buried deep inside a mountain on the remote Arctic islands of Svalbard. There are no earthquake zones or volcanoes nearby, and the area has natural low humidity and temperature. This is perfect for the storage of seeds.

Having seeds in a safe stored environment means that we have a back up if any species die off, including essential plants used for foods. They could potentially solve a world food crisis!

Microorganisms are too small to see without using a microscope. They are classified into two main groups:

1. Bacteria
2. Fungi

Viruses are also microorganisms but are not living things.

Living things can all:

• feed
• grow
• reproduce
• get rid of waste by going to the toilet

Viruses don’t need to feed, they copy themselves rather than grow and they don’t need to go to the toilet. So we classify viruses into their own group.

Bacteria are tiny living things that are so small you can't see them without a microscope. They are made up of just one cell which makes them different from plants and animals that have many cells. Bacteria are everywhere! They live in soil, on your skin and even in your gut.

Think of fungi as nature's recyclers. Just as a recycling plant takes in old materials and turns them into new products, fungi take in dead matter and help turn it back into nutrients for the soil.

A virus is a tiny germ that is much smaller than bacteria. In fact, viruses are so small that you can only see them with a special tool called an electron microscope. Unlike living things, viruses cannot survive on their own. They need to invade a host cell, like a tiny 'hijacker', in order to grow and multiply.

Bacteria – Tiny living things that are so small that they cannot be seen without a microscope. Bacteria are made up of just one cell.

Categories – Groups of animals or plants with shared characteristics.

Cell – A small unit that makes up all living organisms.

Classification – The process of organising living things into categories.

Fungi – Fungi take in dead matter and help turn it back into nutrients for the soil.

Invertebrates – Animals that don't have a backbone.

Microorganisms – A tiny living thing, including bacteria, viruses and fungi.

Microscope – A piece of scientific equipment that can help us see things that are too small for the naked eye, like cells and bacteria.

Organism – Any individual animal or plant.

Species – A group of the same kind of animal or plant.

Taxonomy – The system scientists use to classify living things.

Vertebrates – Animals that have a backbone (spine).

Virus – A tiny germ that is much smaller than bacteria. Viruses cannot survive on their own and need to invade a host cell to grow and multiply.