Biology as level AQA Unit 2 Classification

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similar to one another but different from members of other species- similar genes,therefore close resemblance to one another.

capable of breeding to produce fertile offspring

Naming of species - the binomial system

based upon latin or greek names - First name is called generic name, name of genus of the organism

second name - is the specific name , equivalent to the given name

Rules for writing names - write in italics or if handwritten underline the name to indicate that it is scientific. First letter of generic name is capital the rest of the letters are lower case if the specific name is not known then it can be written as  'sp'

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Grouping of species

Grouping of organisms is known as classification

practise of classification is known as taxonomy

Artificial classification - division accroding to differences such as colour and size

Natural classification - based upon evolutionary relationships between organisms and their ancestors,   classifies species into groups ,  arranges the groups into a heirachy

in natural classification are based upon their homologous characteristics

all systems of classification are set up for human conveinience

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each group within an nautural habitat is known as a taxon.

Taxonomy is the study of these groups and their position in a heirachical order

order of ranks   








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Taxonomy continued

as you go down the ranks the groups get smaller

Phylogeny- the evolutionary relationship between organisms represented by a phylogenic diagram drawn like a tree


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Evidence for relationships between organisms

When organisms evolve both internal and external features change

Dna determines the proteins of an organism including enzymes - proteins determine the features of an organism

Comparing the dna and proteins of differerent species helps the scientists to determine the evolutionary relationships between them

when  one species gives rise to another during evolution they are the very similar however due to mutations have slight differences as time goes on more mutations lead to more differences

we can determine these differences through dna hybridisation

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DNA Hybridisation

Dna Hybridisation depends on helical structure of dna

when dna is heated the double strand seperates into 2 complementary strands.these when cooled can rejoin to form a helix once again

Using this property dna hybridisationcan be used to compare dna of species - dna from 2 species is purified and cut into short peices

 dna from one of the species is labelled with flouresence or radioactive markers

dna from both of the species is then heated and split it is then left to cool so that the dna can form a helix

some of the strands that join together will be a hybrid of both the species we can then test to see how closely related the species are by heating at different temperature stages

the higher the temp needed to split the strand shows how closely the species are related . this is because there will be more hydrogen bonds between the bases as more complementary pairs are made so more energy needed to break the hydrogen bonds

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Dna base sequence

 dna base sequence can be used to classify plants

Comparison of the amino acid sequences in proteins- we can compare species by counting thechanges in amino acids

immunological comparisons of proteins -  principle behind this is that the antibodies of one species will respond to antigens on proteins

the method is  1- inject the antigen fromspecies a into the species b

2- speices b will produce antbodies

3- serum extracted from Species b that contains the antibodies this is mixed with species c antibodies response produce percipitate

4 - more precipitate more closely related

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Courtship Behaviour

Courtship Behaviour is necessary in species for survival

courtship behavior helps to achee survival of the bestby enabling individuals to

- recongnise members of own species

- identify mate that is capable of breeding

-form a pair bond

-synchronise mating

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