Thursday, 3 January 2013

1.2 describe the common features shared by organisms within the following main groups


  • plants
  • animals
  • fungi
  • bacteria
  • protoctists
  • viruses

for each group describe examples and their features
(details of lifecycle and economic importance are not required)

Plants
Multicellular organisms
Their cells contain chloroplasts- able to carry out photosynthesis
Their cells have cellulose cell walls
They store carbohydrates as starch or sucrose
Examples include flowering plants, such as a cereal (for example maize), and a herbaceous legume (for example peas or beans)

Animals
These are multicellular organisms
They have no cell walls
They usually have nervous coordination and are able to move from one place to another
They often store carbohydrate as glycogen
Examples include mammals (for example humans) and insects (for example mosquito)

Fungi
Usually organised into a mycelium made from thread-like structures called hyphae, which contain many nuclei
Some examples are single-celled
Their cells have walls made of chitin
They feed by extracellular secretion of digestive enzymes onto food material and absorption of the organic products (saprotrophic nutrition)
They may store carbohydrate as glycogen
Examples include Mucor (hyphal example) and yeast (single cell example)

Bacteria
These are microscopic single-celled organisms
They have a cell wall, cell membrane, cytoplasm and plasmids
They lack a nucleus but contain a circular chromosome of DNA
Some bacteria can carry out photosynthesis but most feed off other living or dead organisms
Examples include Lactobacillus bulgaricus (used in the production of yoghurt from milk) and Pneumococcus (pathogen causing pneumonia)

Protoctists
These are microscopic single-celled organisms
Some, like Amoeba, that live in pond water, have features like an animal cell
Some like Chlorella, have chloroplasts and are more like plants
A pathogenic example is Plasmodium, responsible for causing malaria

Viruses
These are small particles, smaller than bacteria
They are parasitic and can reproduce only inside living cells
They infect every type of living organism
They have a wide variety of shapes and sizes
They have no 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)






11 comments:

  1. do you have to memorize all of it?

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    Replies
    1. I mean, it's all in the syllabus (as gruesome as it is) ...

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  3. are you triple / separate science??

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  4. The Biology Syllabus has changed.... New Syllabus Blog:

    http://igcse-biology-2017.blogspot.hk

    ReplyDelete
  5. This comment has been removed by the author.

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  6. Find more at:

    http://igcse-biology-notes.blogspot.hk/2017/06/12-describe-common-features-shared-by.html

    ReplyDelete