Classification

Classification

1. Groups

   • Classified depending on how closely related they are
   • Kingdom
     • Plantae
       • Contain chlorophyll and are autotrophs (make own food).
       • Multicellular with a rigid cell wall to support cells.
     • Animalia
       • Heterotrophs so have to find own food (e.g. plants)
       • Multicellular.
       • No cell wall or chlorophyll.
     • Fungi
       • Saprophytes (feed off dead organisms and decaying material).
       • Multicellular with cell wall.
       • No chlorophyll
     • Protoctista
       • Unicellular with nucleus.
       • (e.g. algae)
     • Prokaryota
       • Unicellular without nucleus.
       • (e.g. bacteria)
     • Subdivided into smaller categories that have common features.
       • Phylum, Class, Order, Family, Genus, Species
     • Viruses non-living so belong to no kingdom.
   • The phylum Chordata is made up of vertebrates (with a supporting rod running through their back.
     • Oxygen absorption.
       • Lungs
         • Reptiles,birds and mammals.
       • Gills
         • Fish
       • Amphibians
         • Lungs, gills and skin.
     • Thermoregulation.
       • Homeotherms.
         • Mammals and birds.
       • Poikilotherms
         • Fish, amphibians and reptiles.
     • Reproduction.
       • Viviparous.
         • Mammals.
       • Oviparous.
         • Fish, birds, amphibians and reptiles.
     • Fertilisation.
       • Internal
         • Mammals and birds.
       • External
         • Reptiles, fish and amphibians.
     • Some species don't fit exactly into a particular class. The duck-billed platypus is a mammal however it lays eggs.

2. If organisms are part of the same species they can interbreed to produce fertile offspring however...

   • Some reproduce asexually.
   • 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).
   • There can be a lot of variation (e.g. breeds of dogs).
   • Ring species are related populations in neighbouring areas. Species close to one another produce fertile offspring but ones further apart cannot.

3. 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...

   • Identifying species to avoid confusion where names mean different things in different places.
   • Study species by identifying them research can be shared.
   • Conserve endangered species so we don't confuse similar looking species so that one isn't protected whilst the other becomes extinct.
   • Target conservation efforts by protecting areas with a great variety of species (e.g. tropical rainforests to prevent a huge number being destroyed)

4. 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.