Biology: Classification

Explain the meaning of the term species

- members of a population that can interbreed

- to produce fertile offspring

- they occupy a particular niche

Methods of determining the species which can be used to interbreed

- Morphological - structural features (easiest and quickest to compare but can not cataegorise based on this alone)

- Physiological - they way the body works

- Biochemical - includes the sequence of bases in DNA and the sequence of amino acids in proteins

- Behavioural

Classification: the process of sorting living things into groups

Taxonomy: the study of the principles of classification

Phylogeny: the study of the evolutionary relationships between organisms

Why do we classify things?

• To put things in order to sort them out
• there are nearly 2 million different species of living organisms
• Each species must be placed in a group of similar organisms
• It is for our convenience
• to make the study of living organisms more manageable
• to make it easier to identify organisms
• to help us see the relationship between the species

Classification

Domain        Eukaryotae       Few feautures in common

Kingdom      Animalia            members show more diversity

Phylum        Chordata

Class            Mammalia

Order           Primate

Family          Hominidae

Genus          Homo

Species        Sapiens              more features in common - member shows similarities 

Taxonomy

• A 'taxon' is a unit of classification
• A 'species' is the smallest taxon = basic unit of classification
• Groups of similar species form the next taxon 'genus'
• Groups of similar genera form a 'family'
• Etc. up to the largest taxon, domain.

Difference between phyla are major - easy to decide which one organisms belong to

Chordata - central bundle f nerves running along back

Arthropods - have hard exoskeleton

                 - are subdivided into classes e.g. class insects

The species are classified based on the evolutionary relationships, they are grouped together based on shared, homologous features

These features are similar enough that they have to come forma  similar design e.g. vertebrates have similar limb bones, 1 bone in upper limb, 2 bones in lower limb