Topic 4C

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  • 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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The binomial system

  • All organisms are given an internationally accepted scientific name in latin
  • The first part of the name refers to the genus and has a capital letter
  • The second part is the species which starts with a lower case letter.
  • The names are always written in italics
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Courtship behaviour

  • 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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Classification using DNA or proteins

  • 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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Using gene technologies to assess genetic diversit

  • 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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Investigating variation

  • 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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Agriculture and Biodiversity

  • 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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