Thursday 7 September 2017

1.2 describe the common features shared by organisms within the following main groups: plants, animals, fungi, bacteria, protoctists and viruses, and for each group describe examples and their features

Main Groups of Organisms 

  • Plants
  • Animals 
  • Fungi
  • Bacteria 
  • Protoctists
  • Viruses 


Plants

  • Multicellular organisms
  • Cells contain chloroplast and are able to carry out photosynthesis
  • Cells have cellulose cell walls
  • They store carbohydrates as starch or sucrose

Examples include flowering plants, such as cereal (e.g. maize) and a herbaceous legume (e.g. peas or beans)

Animals

  • Multicellular organisms
  • Cells do not contain chloroplast and are not able to carry out photosynthesis
  • Cells do not contain cell walls
  • They usually have a nervous coordination and are able to move from one place to another 
  • They often store carbohydrates as glycogen 

Examples include mammals (e.g. humans) and insects (e.g. mosquito) 

Fungi

  • Usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei (multicellular)
  • Some examples are single-celled
  • They are saprophytic and feed by excreting digestive enzymes onto food and absorbing the digested products (saprotrophic nutrition)
  • Their cells have walls made of chitin (a protein)
  • They store carbohydrates as glycogen

Examples include Mucor (hyphal/multicellular) and yeast (single cell)

Bacteria

  • These are microscopic single-celled organisms
  • They don’t have a nucleus but contain a circular chromosome of DNA (a bacterial chromosome)
  • Some bacteria can carry out photosynthesis, but most are saprophytes and feed of dead organisms
  • They have a cell wall, cell membrane, cytoplasm and plasmids

Examples include Lactobacillus bulgaricus (a rod-shaped bacterium used in the production of yoghurt from milk) and Pneumococcus (a spherical bacterium that causes Pneumonia) 

Protoctisis

  • Everything else that doesn’t fit in any of the other kingdoms
  • They can be single-celled and multicellular organisms

Some like Amoeba that live in pond water, have animal characteristics
Some like Chlorella have chloroplast and have plant characteristics
A pathogenic example is Plasmodium, responsible for causing malaria 

Viruses
  • Not living organisms 
  • The small particles, smaller than bacteria, not made out of cells
  • They are parasitic and can only reproduce inside living cells (host cells)
  • They can infect every type of  living organisms
  • They do not have a cellular structure but have a protein coat and contain one type of nucleic acid,  either DNA or RNA
Examples include the tobacco mosaic virus, the influenza virus (causes “flu”) and the HIV virus (causes AIDS)

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