Classification

Classification

Classification schemes sort organisms into groups based on characteristics that they share.As we progress from Kingdom to species, the organisms share more characteristics in common.The species is the basic category of classification.

Why classifyScientists use classification to help them• Identify organisms by recognising characteristics shared by their group• Identify relationships within the groups and look for evolutionary trends .• Describe new organisms quickly and accurately• Communicate more easily with other biologists

Biologists who specialise in classification are called taxonomists. The study of classification is called taxonomy.

Classification schemesClassification schemes can change as • we discover new organisms that

don’t fit neatly into a current category eg Euglena

• advances in technology show new characteristics or new relationships between organisms eg chitin cell wall of fungi, DNA sequencing

Characteristics used in classification 1 1. Structural similarity (morphology) • Animals - structures such as skeleton, fur,

scales and body parts• Plants - structures like leaves, roots or stem

structure as well as means of reproduction.

Characteristics used in classification 2Structure can be misleading as some groups may share a common feature but are from very different groups (eg bats, birds and some insects have wings), so taxonomists look at evolutionary history and supporting internal structures help make classification decisions. Sometimes they must go further and look at blood proteins, DNA and even embryos to help make decisions.

Colour, size and habitat are not usually used at major grouping levels because these can vary between different populations, sexes or at different ages or stages of life.

Characteristics used in classification 32. Means of reproduction (e.g. sexual, asexual, internal, external, flowers, cones, seeds, spores or fruits).

Often we combine structural and reproductive features.

Classification of humans

Scientific NomenclatureOrganisms are identified by two names – their Genus and species namesGenus is always capitalised and species is always lower caseThe Genus species is usually italicized and/or underlined

Naming organismsMost names come from Latin words describing a colour or feature (eg rufus = red, macro = big, pus/pod = foot, giganteus = big, agilis = agile)Sometimes a species may be named after a person (usually the scientist that discovered it eg bernardus)

Agile Wallaby

 

Black Wallaroo

 

Eastern Grey Kangaroo

 

Red Kangaroo

Macropus agilis

 

Macropus bernardus

 

Macropus giganteus

 

Macropus rufus

Classification keys

Keys are used to help identify organisms.Dichotomous keys are ones that divide the group into twos.

Dichotomous keys

Table keys

Flow chart keys