The invertebrates - the little things that run our world

Invertebrates make up 99% of animal life on Earth.

On this site you will find descriptions and images of the various invertebrate phyla (the plural of phylum). If you are not sure where to look try the search box at the top right, or the tables on the left and below.

The invertebrates are the little things that run our world.

Because of our great size we tend not to notice invertebrates, but they were here long before us, and will be here long after we are gone (see my rant at the bottom of the page). And it would do our egos good to remember that without them we would soon die, but if all of us vanished tomorrow they would hardly notice.

Take the sponges - yes your bath sponge is an animal, actually it is a colony of animals. They've been around for more than 600 million years, and there is no reason to think that they will not continue for another 600 million years.

In the average patch of Amazonian rainforest 93% of the dry weight of animal tissue is invertebrate according to Edward O. Wilson, the Harvard ecologist and ant expert.

A hectare of good quality soil has about 1000 kg each of earthworms and arthropods (uniramia, chelicerata) according to David Pimentel of Cornell University.

The sheer diversity of the invertebrates is stunning. Look at the antennae (feelers) below. These are just some of the the different kinds you can find on the insects in a British garden.

Britain is a small island. It has what is termed a depauperate fauna. What that means is that the ices ages caused the extinction of most species in Britain, and since the retreat of the ice relatively few species have made their way back compared to continental Europe.

Yet in this little, species-poor island, in any garden you can find such a diversity of insects. Of course this great diversity leads to one particular difficulty, and that is identification. When you see a bird in your garden and want to know what it is, you can easily find its picture in any bird book, but if you wanted to do the same for the beetle you found under a stone it would be a different story. There are over 4000 species in the U. K. and that is just one order of insects which are part of one of more than 30 phyla!


If you are trying to identify or want to know more about an invertebrate, but don't know where to start, and the list above hasn't helped, then try the table below.

I've separated the invertebrates out by body shape, but do remember that this is just a rough and ready guide, and you won't find it in any academic textbook. Or you could try my new book availble from Amazon if it is an insect.

Smith, L. (2014). Characteristics of the insect orders. Amazon. Characteristics of the insect orders with drawings and photographs to help you understand the differences between the different types of insect, and identify which order an insect is in, as well as fast facts about each insect order, and links to web pages with more detailed information. Many orders have separate sections about the life cycle of the insect as well as its habitat requirements, and fossil history.

a small selection of different types of insect antennae
Things with 6 or more legs
Things that look like worms
Things that have a shell
Things that have a radial body pattern
Tiny things in water
  • Crustacea - these can have tiny larvae that look nothing like the adult.
Things that don't fit in anywhere else
  • Sponges (tiny animals that can form large colonies)
  • Bryozoa (moss animals - tiny, colonial and sometimes mistaken for sponges)
  • Entoprocta (tiny, colonial, aquatic and rare)
  • Rotifera (tiny, mainly freshwater or moist habitats, common, but usually overlooked)
  • Placozoa (tiny, marine, rare and little is known about them)

Animal Kingdom

Above a diagram showing the major division of the animal kingdom.

Global warming and pollution - my rant

Global warming and pollution caused by us are having a real effect on the Earth. Species are going extinct in numbers higher than the normal background rate. However what is all this compared to Earth's past history which is measured in millions of years, while our recorded history is just a few thousand years, and as a species just a few hundred thousand years?

We are destroying the Earth as we know it, but we are not destroying the Earth. Nothing in human power can come close to the catastrophes the Earth has weathered in the past. Neither atomic bombs nor global warming at its worst will be as severe as the mass extinctions caused by the meteor impact in the late Cretaceous. It is estimated that this impact wiped out half the marine species, as well as leading to the demise of the dinosaurs.

Yet the earth recovered, and the small, hairy mammalian afterthought that was our ancestor prospered. But even this was as nothing to the huge catastrophe in the Permian, which is estimated to have caused the extinction of 95% of species. And the Earth went on and life continued, and species evolved.

So when we moan and groan about global warming and pollution it is OUR world we want to save. OUR species, OUR furry, feathery animals. The trees and plants WE like to look at and smell and eat.

And if we fail? Well many of them will go extinct along with us, but the Earth will go on. It will turn on its axis and the sun will rise. And life will go on. Some species will prosper in the new conditions, and other species will undergo changes, and divisions will occur and new species will emerge.

Humans do not have the power to snuff out life, but we do have the power to snuff out species and change the world into something we cannot live in. So, do we keep this little paradise we have, or do we shuffle off and leave it to more adaptable species?

The choice is yours, isn't it?

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