• Created by: tia5sos
  • Created on: 22-11-20 18:15
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  • classification
    • classification is organising living organisms into groups
      • looking at the similarities and differences between organisms allows us to classify them into groups.
      • Scientists have been doing this for thousands of years but the way in which organisms are classified has changed over time.
      • there are two different classification systems, artificial and natural.
    • artificial classification systems use observable features
      • early classification systems only used observational features (things you can see) to place organism's into groups, e.g. whether they lay eggs or can fly. This system of putting organisms into groups is known as artificial classification system.
      • artificial classification systems are still used to make keys so that scientists can easily identify and group organisms but they're no longer seen as the best way to classify organsims.
    • natural classification systes use evolutionary relationships
      • 1. As people began to understand more about evolution, evolutionary relationships became much more important when classifying organisms
      • 2. Natural classification systems use information about organisms' common ancestors and about their common structural features to sort organisms.
        • For example, even though bats and humans have many differences, the bone structure of a bat wing is similar to that of a human hand, so in the natural classification system, bats and humans are grouped together.
      • 3. in natural classification systems, living things are divided into 5 kingdoms (e.g. the plant kingdom, the animal kingdom).
      • 4. the kingdoms are then subdivided into smaller and smaller groups - phylum, class, order, family, genus, species.
      • 5. The hierarchy ends with species - the groups that contain only one type of organism (e.g. humans, dogs, E.coli)
        • a species is defined as a group of similar organisms that are able to reproduce to give fertile offspring
    • developments in biology lead to improvements in classification
      • as technology improves, scientists are able to learn more and more about organisms and how they're related to each other.
      • many years ago, the invention of the microscope helped scientists to classify organisms as they could examine the structure of organisms in more detail.
      • Nowadays, as well as improvements to microscopes, other new technologies are resulting in new discoveries being made and the relationships between organisms being clarified.
        • for example, new evolutionary relationships are continually being discovered through molecular phylogenetics
      • DNA sequencing is used in molecular phylogenetics to see how closely related organisms are
      • DNA sequencing is a technique that compares the sequence of DNA bases for different species. The more similar the DNA sequence between species, the more closely related they are. E.g. the base sequence for human and chimpanzee DNA is about 94% the same.


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