Backyard Biodiversity
About Invertebrates
- What are invertebrates?
- Why are invertebrates important?
- Classifying invertebrates
- What's in your backyard?
- Syllabus links for teachers
- Current Museum invertebrate projects
What are invertebrates?
The animal kingdom is divided into vertebrates and invertebrates. Vertebrates have a vertebral column (backbone) whereas invertebrates do not. There are about 40,000 species of vertebrates. At least 99% of all animal species are invertebrates, comprising over 30 major groups and over 5 million species.
Invertebrates:
- include insects, crustaceans (eg. crabs), spiders, coral;
- are found in all aquatic and terrestrial environments; and
- are usually smaller than vertebrates, but can range in size from microscopic forms to giant squids.
Why are invertebrates important?
Invertebrates affect all other forms of life by sheer weight of numbers. They make up the bulk of biodiversity. Invertebrates are essential for maintaining the function of ecosystems for many reasons. For example:
- They form an integral part of the food web.
- They recycle organic matter, feeding on faeces or dead plants and animals.
- They make up the bulk of parasite species (along with microorganisms such as bacteria that regulate animal and plant numbers).
So little is known about the diversity of invertebrates, with so many species yet to be identified, it is impossible to understand their full ecological value. For this reason it is important to conserve and promote invertebrate biodiversity.
Classifying invertebrates
Most of the invertebrates you are likely to collect in this study will probably belong to the phylum Arthropoda. Arthropods and other small invertebrates are sometimes known by the lay term 'minibeasts'.
The diagram below shows the scientific criteria used for classifying various 'minibeasts' into the large group called arthropods and its smaller sub-groups. The next few pages list some of the minibeasts you might find, showing which phylum they belong to.
Examples of animals in each arthropod sub-group
- Insects include bees, butterflies, beetles, ants, moths, praying mantids, cicadas, cockroaches, fleas, wasps and flies.
- Arachnids include spiders, scorpions, pseudoscorpions, ticks and mites.
- Crustaceans include crabs, shrimps, prawns, lobsters, crayfish and slaters.
- Myriapods include centipedes and millipedes.
