The Animal Kingdom Project

The Animal Kingdom

This is a short explanation of some biological terms, just so that you don’t feel ignorant if your child comes home wildly excited about a creature you’ve never heard of.

When we look at animals we sometimes look at the different phylum – a different kind – of creature. The phyla are listed below.

(Phylum is the biological term for the groups of creatures that make up a Kingdom, such as that of plants or animals.)

Animals

The word “animal” comes from the Latin word animale and is derived from anima meaning vital breath or soul. The colloquial usage of the word refers, usually, to non-human animals. The biological definition of the word though refers to all members of the Kingdom Animalia, including humans.

There are more than one million species of animals in at least 30 phyla, more species than all the other kingdoms combined. More than half of all animal species are insects (800,000 species). Animal phyla are classified according to certain criteria, including type of body cavity(coelom), symmetry, body plan and presence of segmentation. From the more than 30 phyla mentioned as creating the Animal Kingdom, these are the most significant ones:

Protozoa – single-celled non-photosynthetic organisms. Now part of the kingdom Protista.
(The other phyla are all metazoa – multicellular organisms):
Porifera – sponges
Coelenterata – jellyfish, sea anemones, corals and hydras. The old phylum Coelenterata was merged with the ctenophora (‘comb-jellies’) to create the new phylum Cnidaria.
Annelida – worms
Mollusca – snails, shellfish, squid, octopi
Arthropoda – crabs, spiders, insects
Echinodermata – sea urchins, starfish, sea cucumbers
Chordata – fish, dinosaurs, cats, whales, us.

Note: Everything changes, including taxonomy – the science of naming and classifying creatures. Our project sequence still follows the old division of life forms into the 2 kingdoms of Animals and Plants (Animalia and Plantae), which has been replaced by a 5-kingdom division, The five kingdom division of life can be summed up as: Monera, Protista, Fungi, Plantae and Animalia. There is, however, still squabbling between gangs of taxonomists about how kingdoms should be defined, exactly how many kingdoms there “really” are, the relationships between them, whether any of them should be considered sub-kingdoms of each other and so on.

But it’s still valuable to learn the old definitions, and learn that they’ve changed and why, since this helps teach that scientific knowledge alters and improves as we learn more, and sometimes old ways of looking at things need to be changed in the light of new knowledge.

Glossary:

Taxonomy is the biological science of classifying living creatures into a hierarchy of related groups. The groups are called taxa (taxon in the singular). This system was proposed by Carl Linnaeus in his book Systema naturae in 1735 and is still followed today, though there have been changes to the arrangements of the taxa within the Linnaean system as our knowledge has increased.

The taxa are, from the largest to the smallest:

• kingdom: The largest grouping. We used to talk about the animal and plant kingdoms, but these days biologists divide living things into five kingdoms; the familiar Animalia (animals), Plantae (plants) and Fungi (mushrooms, mould, and lichens), and the less familiar Protista (basically, anything eukaryotic – which means their cells have nuclei – that doesn’t quite fit in the first three. Includes protozoa) and Monera (all prokaryotic creatures like bacteria and blue-green algae, whose cells don’t have nuclei).
• phylum (pl. phyla): The kingdoms are divided into phyla, which are divided into classes, which are further divided into orders, which are subdivided into families, then into genera (sing. genus) which are then divided into species. The genus and species names make up the familiar scientific name of a species, like Homo sapiens or Tyrannosaurus rex.

In general, the larger the taxon, the longer ago the creatures evolved apart and the wider the variety of creatures in that taxon.

Using us – Homo sapiens – as an example, the species sapiens evolved more recently than the genus Homo. Fossils of other members of our genus have been found and named, e.g. Homo erectus and Homo habilis. They’re enough like us to be in the same genus, but different enough to not be the same species. Going further up the ladder, genus Homo is part of the family Hominidae, the hominids, which also includes the extinct genus Australopithecus. This family belongs to the order of Primates, as do chimps, gorillas and monkeys. Primates are part of the class Mammalia, the mammals, which belongs to the phylum Chordata, creatures with spinal cords, which is a part of the kingdom Animalia, the highest and most general level.

Recommended reading: Anything by Stephen Jay Gould, who’s the most lucid and understandable writer around on evolution, biology and science in general..

Links: It’s very hard to find sites that don’t assume some basic knowledge, but these may help: this encyclopaedia entry on classification, the University of California’s Museum of Paleontology website and the Tree of Life web project.

The Woods Hole Marine Biological Laboratory’s website has a beautiful gallery of 19th-century wallcharts showing all the phyla.

See pictures of origami arthropods on line!