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.
Kingdom to species
You will remember from your Key Stage 3 studies that species with similar characteristics are put into groups, and that this is called classification. Remind yourself of the basics of classification.
The first rank in this system is called a kingdom. There are five kingdoms, based upon what an organism's cells are like:
/animalia (all multicellular animals)
/plantae (all green plants)
/fungi (moulds, mushrooms, yeast)
/prokaryotae (bacteria, blue-green algae)
/protoctista (Amoeba, Paramecium).
There are several further ranks before we reach a particular species. In order, these are:
For example, lions have the following classification:
kingdom - animal
phylum - vertebrate
class - mammal
order - carnivorous
family - cat
genus - big cat
species - lion.
One way to remember this is by using a daft sentence like this one:
"Kevin plays clarinet or flute - grotty sound!"
All organisms are known by their binomial name which is the genus and species eg Homo sapiens – modern humans
Classification - Higher tier
Being able to classify species is important to scientists as it allows them to accurately identify individual species wherever they are. For example - a robin in America isn’t the same as a robin in the UK so by using the binomial name Turdusmigratorius (American robin) or Erithacusrubecula (UK robin) then there is no confusion.
Binomial classification is important because it can:
clearly identify species
study and conserve species
target conservation efforts.
The first big division of living things in the classification system is to put them into one of five kingdoms. These are based on what an organism's cells are like. This table shows the names of the kingdoms, the characteristics and examples of the sort of organisms they contain:
It can also be difficult to classify a certain organism. For example, the single-celled organism called Euglena has some confusing characteristics. It has:
chloroplasts, like a plant
no cell wall, like an animal
a flagellum to swim with, like some bacteria.
A fifth kingdom, called the protoctista, was made for organisms like Euglena.
Scientists do not classify a virus as a living thing. This is because:
it does not show all seven processes for life
when it enters a cell it changes the way a cell works so it can make copies of the virus.
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).
Assigning vertebrates to different groups can be difficult as some fall into many categories: for example, sharks are fish but give birth to live young and use internal fertilisation.
What is a species?
Organisms of the same species:
have more characteristics in common than they do with organisms of a different species
can 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.
Similar species tend to live in similar habitats, and are closely related in evolutionary terms. They are likely to share a relatively recent ancestor. Closely related species living in different types of habitat may have different characteristics. You can use keys to identify organisms according to their features.
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.
Sometimes classification can be complicated by:
variation within a species
hybridisation (closely related species breed to produce offspring that have characteristics of both – the hybrids are often infertile)
ring species – neighbouring populations of species may have slightly different characteristics but can still interbreed as part of a chain but the two ends of the chain can’t interbreed.