MAJOR GROUPS OF ORGANISMS

•Biologists classify organisms, putting them into groups.

•Each group reflects similarities of structure and function that have come about because the organisms in the groups.

•Each group reflects similarities of structure and function that have come about because the organisms in the groups are related through their common ancestry.

•In other words, they are descended from the same ancestors by the process of evolution.

1. Plants

•Plants are multi-cellular organisms

•They vary greatly in size from over 100 metres to 50mm

•They contain chloroplasts for photosynthesis

•All plant cells have a cell wall made of a sugar carbohydrate called cellulose

•Plants can make a variety of other carbohydrates from the process photosynthesis, these include starch which is used as an energy store and also sucrose (table sugar)

Examples: Pea Plant, Maize Plant, Oak Tree, Venus Fly Trap

2. Animals

•Animals are multi-cellular organisms

•They vary greatly in size from over 30 metres to smaller than 1mm

•They DO NOT contain chloroplasts

•Animal cells DO NOT have a cell wall

•Most animals store their energy in the form of the carbohydrate glycogen

•Not all bacteria are bad- some can do good and useful things inside out bodies

Examples: House fly, Jelly Fish, Lion

3. Fungi

•Some fungi can be seen with the naked eye and are multi-cellular including mushrooms and some are made from single cells, like yeast

•Fungi can have lots of different shapes

•Fungus cells are a similar to plant cells in that they have a cell wall BUT it is made from chitin

•They differ to plant cells as they DO NOT contain chloroplasts

•Some fungi send out threads which grow into the body of a dead organism known as hyphae

•They respire, releasing carbon dioxide

•They reproduce by releasing spores or by budding (in yeast)

•Some fungi are useful

•You can get rid of a fungal infection with a fungicide

Examples: Athletes foot, mould that produces penicillin, yeast

4. Protosists

•The Protista, or Protosista, are a kingdom of simple organisms, usually composed of a single cell or a colony of similar cells. Protists live in water, in moist terrestrial (land) habitats, and as parasites and in the bodies of multicellular eukaryotes (organisms which cells contain a true nucleus).

•Protists are single-celled and usually move by cilia (hair like projections) or by flagella (tail-like projections). There is usually no cell wall, although some forms may have a cell wall. They have organelles (components of a cell) including a nucleus and may have chloroplasts, so some will be green and others won't be. They are small, although many are big enough to be recognized by a microscope or even with a magnifying glass. Protists get their nutrition by photosynthesis, ingestion of other organisms, or both.

5. Bacteria

•Bacteria are single celled organisms

•They can be a range of different shapes and sizes, usually about 0.001mm or 1mm

•All bacteria have a cell wall

•All bacteria have free, circular DNA that is not in a nucleus

•Bacteria can divide just like other cells

•They divide most rapidly if the conditions are just right for that particular bacteria

•You can get rid of a bacterial infection with antibiotics

•Not all bacteria are bad- some can do good and useful things inside out bodies

Examples: Salmonella (food poisoning), streptococcus (sore throat), lactobacillus (used to make yoghurt)

6. Viruses

•Viruses are very small (about 0.01 mm)

•They are made of DNA and protein

•They are not cells- they don’t have a nucleus and can’t reproduce on their own

•To reproduce, they have to enter a living cell and can only succeed by relying on other living cells (they are parasites). The cell is given instructions by the viral DNA to produce lots more of the virus

•Viruses can lay dormant for years before they become active in a living cell

•Viruses can be transmitted through air, blood, faeces…pretty much any way. They just need a live cell to start dividing when they reach their destination.

•They can be fought off by the immune system in the body and vaccines, but antibiotics have no effect on them

Examples: cold virus, influenza, measles, tobacco mosaic virus (effects the tobacco plant)