Topic 4C

Phylogeny

Phylogeny is the study of the evolutionary history of groups of organisms. It tells us who's related to whom and how closely related they are.
The tree shows a common ancestor and each branch shows how species have evolved to become different species

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Taxonomy is the science of classification and involved naming and organising them into groups.
There 8 levels of groups that are used to classify organisms
The groups are called taxa and each group is called a taxon.
The groups are arranged into hierarchy with the largest at the top and the smallest at the bottom and organisms can only belong to one group at each level
First the organisms are sorted into 3 large groups called domains- Eukarya, bacteria and archaea. Related organisms in a domain are sorted into smaller groups
Organisms are classified into; Domain, Kingdom, Phylum, Class, Order, Family, Genus and Species

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Courtship behaviour is carried out by organisms to attract a mate of the right species
Simple courtship behaviour- using sounds and visual displays
Complex courtship behaviour- dancing and building
You can use courtship behaviour to classify species
Courtship behaviour is specific to a certain species, this means that only members of the same species will carry out and respond to the same behaviour and prevents the wrong species from mating
Examples include fireflies who give off flashes of light and this is specific to the species of firefly, the noise that crickets make is different depending on what species that it belongs too.

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Advances in technology has allowed us to determine the entire base sequence of an organisms DNA
We can compare base sequences and see how see how closely related the organisms are.
The sequnce of amino acids in a protein is coded for the same base sequence in DNA
Related organisms have similar DNA sequences and so similar amino acid sequences
Similar proteins will also bind to the same antibodies

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Early estimates of genetic diversity were made by looking at the frequency of measureable or observable characteristics
Since different alleles determines different characteristics a wide varitety of characteristics in a population indicates a high number of different alleles.
New technologies allow us to give more accurate estimates of genetic diversity within a population of species.
They allow us to compare genetic diversity alot more easily

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Variation is the differences that exist between individuals and there is variation between species and within species.
Variation can be caused by genetic factors such as genes and different alleles.
Variation can also be caused by environmental factors such as climate and food
Most variation is caused by a mixture of both
When studying variation you normally look at a sample population and not the whole thing.
To make sure the sample is biased random sampling is used this means that conclusions can be drawn without and experimenter bias.

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Biodiversity is the variety of living organisms in an area
A habitat is the place where an organsim lives
A community is all the populations of different species in a habitat
Local biodiversity- you could consider the variety of different species in a small habitat
Global biodiversity- you could consider the varity of species that live on earth.
Species richness- is a measure of the number of different species in a community
Index of diversity- its calculated using an equation that takes into account the number of the species in a community and the abundance of each species

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Woodland area is removed to make way for more farmand, this directly reduces the number of trees and also destroys habitat that some species live in
Pesticides are used to kill organisms that feed on crops, this reduces biodiversity as it directly kills the organism
Monoculture is when farmers have fields with only one type of plant, having a sinlge plant will reduce biodiversity directly and will support fewer organisms
Conservation schemes try to strike a balance between maintaining the environment and also promoting biodiversity.

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