The concept of species
Species - a group of anatomically and biochemically similar organisms that can interbreed and produce fertile offspring.
Binomial system - a system whereby living organisims are given two names based on Latin. The first is the genus and the second is the species of the organism.
- Kingdom - Animalia
- Phylum - Chordata
- Class - Mammalia
- Order - Primates
- Family - Hominidae
- Genus - Homo
- Species - sapien
Evidence used in classification
Biochemical - analysing amino acid sequence of a common protein e.g. cytochrome c. Less amino acids in commom = less related. DNA hybridisation - single strand from different species paired up, bond where complementary. Then heated, longer time taken for DNa disassociation = more in common
Anatomical - smilar anatomical structure = more closely related. E.g. 5 digit limb common in almost all vertebrates, this is how we know dolphins are more closely related to us than fish - dolphins flippers are similar to our hands
Embryological - similar stages of pre-natal development due to common ancestor
Immunological evidence - similarities between antibodies in one organism and the antigens in another. If your blood was injected into a genetically similar species you would expected them to have the correct antibody
Behaviour - covers a wide range of traits from courtship rituals to vocalisation, facial expressions, feeding, hunting habits etc.
Natural selection - process by which the best-adapted organisms in a population survive, reproduce and pass on their alleles to their offspring.
Speciation - the development of new species. Happens when different populations of the same species evolve in different ways, speciation is normally thought to happen by a gradual process.
- A mutation creates a variation in the 'giraffe' population.
- There is too much competition for food at ground level for all the organisms to survive.
- Those giraffes with long necks have an increased chance of survival, and therefore successful reproduction. As they can avoid competition by reaching food at higher levels.
- Offspring will inherit the allele, over many generations mutation becomes common place in the population.
Fossil - any form of preserved remains from a living organism .
Carbon dating - a method of dating artefacts up to 50,000 years old. It measures the ratio of 14C to 12C in a sample.
Potassium-argon dating - a method of dating volcanic rocks, based on the fact that 40K decays in 40Ar at a known rate. Scientist can work out age of sample by finding out how much 40Ar it contains.
Stratigraphy - the study of layers in rocks. Generally, older rocks lie below newer ones, so this enables rock layers to be dated.