4C: Diversity and Classification

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Classification of Organisms

Phylogeny: Study of evolutionary history of groups of organisms. Whos related to whom, how closely related. Phylogenetic tree shows relationship between members and common ancestors. Branch points represent a common ancestor from which a different group diverged. 

Taxonomy: Science of classification. Naming organisms&organising them into groups. Easier to identify&study them. Groups = taxa, 1 group = taxon. Groups arranged in hierarchy, largest groups at top, smallest at bottom. Organisms only belong to 1 group at each level in hierarchy, no overlap.

Domain (Eukarya, Bacteria, Archaea), Kingdom, Phylum, Class, Order, Family, Genus, Species (able to reproduce to give fertile offspring)

Binomial system: Scientific Latin name. 1st part = genus name, begins with capital letter. 2nd part = species name, lowercase. Written in italics or underlined if written. Allows scientists to communicate about organisms in standard way, avoids confusion of common names.

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Classification Using Courtship Behaviour

Simple courtship behaviour: Releasing chemicals, sound, visual displays

Complex: Dancing, building

It is species specific - only members of same species will do and respond to that courtship behaviour. Allows members of same species to recognise each other, preventing interbreeding and making reproduction more successful. Because of specificity, courtship behaviour can be used to classify organisms. More closely related species are, more similar courtship behaviour.

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Classification Using DNA Proteins

Genome sequencing: DNA base sequence of one organism can be compared to DNA base sequence of another to see how closely related. Closely related = higher % of similarity in DNA base sequence.

Amino acid sequence: Proteins made of amino acids. Sequence of amino acids in protein coded for by base sequence in DNA. Related organisms have similar DNA sequences and so similar amino acid sequences in proteins.

Immunological comparisons: Similar proteins will also bind same antibodies. If antibodies to a human version of a protein are added to isolated samples from some other species, any protein thats like the human version will also be recognised by that antibody.

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Gene Technologies

GD used to be measured by frequency of measureable or observable characteristics in population. Different alleles determine different characteristics so wide variety of each characteristic in population indicates high number of different alleles, ergo GD.

Different alleles of same gene will have slightly different DNA base sequences. Comparing DNA base sequences of same gene in different organisms in population allow scientists to find out how many alleles of that gene there are in that population. 

Different alleles will also produce slightly different mRNA base sequences, and may produce proteins with slightly different amino acid sequences, so these can also be compared.

Can give more accurate estimates of GD within population and allow the GD of different species to be compared more easily.

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Investigating Variation

Variation: Caused by genetic factors. Different species, different genes, causes variation between species. Individuals of same species have same genes, but different alleles; causes variation within species. Caused by differences in environment.

When studying variation within a species, usually only look at sample. Too time consuming or impossible to catch all individuals in group.

Sample used to draw conclusions about whole populations, so must accurately represent whole population and make sure patterns observed not due to chance.

To make sure sample isnt biased, must be random. E.g. Divide field into grid and use random no. generator to select coordinates. Need to analyse results statistically to be more confident that results are true, therefore will reflect whole population.

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Biodiversity

Biodiversity: Variety of living organisms in an area. Habitat: Place where an organism lives. Community: All the populations of different species in habitat. Local or global level.

Species richness: Measure of no. of different species in community, simple measure. Worked out by taking random samples of community and counting no. of different species. 

Index of diversity: Higher no. = more diverse area. If all individuals same species, index = 1.

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Agriculture and Biodiversity

Biodiversity reduced by farmers trying to maximise yield from area of land.

Wood clearance to increase area of farmland. Directly reduces no. of trees, sometimes no. of different tree species. Destroys habitats, so some species can lose shelters/food source. Some species die or migrate to suitable area, further reducing biodiversity.

Hedgerow removal increases farmland area, turns small fields into larger fields. Reduces BD.

Pesticides kill organisms that feed on crops. Reduces diversity by directly killing pests. Species that feed on pests will lose food source, so numbers decrease.

Herbicides kill unwanted plants. Reduces plant diversity, reduces organisms that feed on weeds.

Monoculture; field contains only 1 type of plant. Reduces BD directly, supports fewer organisms.

Conservation: Give legal protection to endangered species, SSSIs, AONBs, The Environmental Stewardship Scheme.

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