Classification

Classification

Groups
1. Classified depending on how closely related they are
2. Kingdom
  1. Plantae
    1. Contain chlorophyll and are autotrophs (make own food).
    2. Multicellular with a rigid cell wall to support cells.
  2. Animalia
    1. Heterotrophs so have to find own food (e.g. plants)
    2. Multicellular.
    3. No cell wall or chlorophyll.
  3. Fungi
    1. Saprophytes (feed off dead organisms and decaying material).
    2. Multicellular with cell wall.
    3. No chlorophyll
  4. Protoctista
    1. Unicellular with nucleus.
    2. (e.g. algae)
  5. Prokaryota
    1. Unicellular without nucleus.
    2. (e.g. bacteria)
  6. Subdivided into smaller categories that have common features.
    1. Phylum, Class, Order, Family, Genus, Species
  7. Viruses non-living so belong to no kingdom.
3. The phylum Chordata is made up of vertebrates (with a supporting rod running through their back.
  1. Oxygen absorption.
    1. Lungs
      1. Reptiles,birds and mammals.
    2. Gills
      1. Fish
    3. Amphibians
      1. Lungs, gills and skin.
  2. Thermoregulation.
    1. Homeotherms.
      1. Mammals and birds.
    2. Poikilotherms
      1. Fish, amphibians and reptiles.
  3. Reproduction.
    1. Viviparous.
      1. Mammals.
    2. Oviparous.
      1. Fish, birds, amphibians and reptiles.
  4. Fertilisation.
    1. Internal
      1. Mammals and birds.
    2. External
      1. Reptiles, fish and amphibians.
  5. Some species don't fit exactly into a particular class. The duck-billed platypus is a mammal however it lays eggs.
If organisms are part of the same species they can interbreed to produce fertile offspring however...
1. Some reproduce asexually.
2. Hybrids from 2 different species can be fertile (e.g. mallard with yellow-billed duck) but they are not the same species because they have many differences (e.g. genetics).
3. There can be a lot of variation (e.g. breeds of dogs).
4. Ring species are related populations in neighbouring areas. Species close to one another produce fertile offspring but ones further apart cannot.
Binomial system gives each species a 2 part latin name. The first part is the genus and the second is the species (e.g. humans are Homo sapiens). This helps scientists by...
1. Identifying species to avoid confusion where names mean different things in different places.
2. Study species by identifying them research can be shared.
3. Conserve endangered species so we don't confuse similar looking species so that one isn't protected whilst the other becomes extinct.
4. Target conservation efforts by protecting areas with a great variety of species (e.g. tropical rainforests to prevent a huge number being destroyed)
Keys can be used to decipher a species by answering a series of questions to narrow down the possibilities until you are left with just one.

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