The vertebrates are animals with a backbone. Scientists separate this group into smaller groups because of their features:

• how the animal takes in oxygen – lungs, gills or through the skin
• thermoregulation – maintains own temperature(homeotherms)or temperature varies with surroundings(poikilotherms)
• reproduction – internal or external fertilisation, lay eggs(oviparous)or give birth to live young(viviparous).
  

Group Characteristics

Fish: Gills, external fertilisation, Oviparous, poikilotherm

Amphibian: Some lungs or gills, external fertilisation, Oviparous, poikilotherm

Reptile: Lungs, internal fertilisation, Oviparous, poikilotherm

Bird: Lungs, internal fertilisation, Oviparous, homeotherm

Mammal: Lungs, internal fertilisation, Vivaparous, homeotherm

What is species?

Organisms of the same species:

- have more characteristics in common than they do with organisms of a different speciescan

- interbreed to produce fertile offspring.

Sometimes a species may have different kinds or breeds that show great variation but the individuals still belong to the same species. Different breeds of pedigree dog are like this.

A species is defined as organisms that produce fertile offspring but this is sometimes limited as some organisms do not always reproduce sexually, and some hybrids are fertile

Kingdoms

The first rank in this system is called a kingdom. There are five kingdoms, based upon what an organism's cells are like:

1. animalia (all multicellular animals)
2. plantae (all green plants)
3. fungi (moulds, mushrooms, yeast)
4. prokaryotae (bacteria, blue-green algae)
5. protoctista (Amoeba, Paramecium).

Classification is the method used by scientists to order living organisms. All species have a unique classification that results in a binomial name. Vertebrates are an example of a classification group. Keys can be used to help to identify individual organisms.

Further divisions

There are several further ranks before we reach a particular species. In order, these are:

• kingdom
• phylum
• class
• order
• family
• genus
• species.

Animalia; Multicellular, no cell wall or chlorophyll, heterotrophic feeders.

Plantae; Multicellular, have cell walls and chlorophyll, autotrophic feeders.

Fungi; Multicellular, have cell walls, do not have chlorophyll, saprophytic feeders.

Proctista; Usually unicellular, with a nucleus eg amoeba.

Prokaryotes; Unicellular, with no nucleus eg bacteria. Examples: bacteria and blue-green algae