Biology: Chapter 2

Brief notes on Chapter 2: The Variety of Living Organisms

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  • Multicellular organisms.
  • Cells never contain chloroplasts - cannot carry out photosynthesis.
  • Gain nutrition by feeding off other organisms.
  • Cells do not have cell walls - cells can change shape.
  • Movement is usually achieved by using coordination by a nervous system.
  • Carbohydrate is stored in their cells as glycogen.
  • Only mammals, birds, reptiles, amphibians and fish are vertebrates.
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  • Multicellular organisms.
  • Cells contain chloroplasts to carry out photosynthesis.
  • Photosynthesis uses light energy to convert simple inorganic molecules (e.g. water and carbondioxide) into complex organic compounds.
  • Cells have a cellulose cell wall.
  • Cells have a vacuole to store dissolved sugars, mineral ions and other solutes.
  • Carbohydrates are stored as starch and sugar is stored as sucrose.
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  • Some groups of fungi are multicellular (e.g. mushrooms, moulds).
  • Some groups of fungi are unicellular (e.g. yeast).
  • Cells never contain chloroplasts - cannot carry out photosynthesis.
  • Cells have a chitin cell wall.
  • A mushroom/toadstool has hyphae underneath the soil.
  • A network of hyphae is called mycelium.
  • Moulds feed by absorbing nutrients from dead material.
  • Hyphae secrete digestive enzymes to break down soluble substances which are then absorbed by the mould.
  • Saprotrophic nutrition is when an digestion takes place outside of the organism.
  • Enzymes that are secreted outside of the cells for saprotrophic nutrition are called extracellular enzymes.
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  • Most are unicellular organisms.
  • Seaweeds are multicellular protoctists.
  • Some are like animal cells and are called protozoa.
  • Others are like plant cells, as they have chloroplasts for photosynthesis.
  • Some protoctists are agents of disease (e.g. plasmodium causes malaria).
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  • Unicellular organisms.
  • Cells have a cell wall made up of proteins and polysaccharides.
  • Some species of bacteria have a capsule or slime layer around the cell wall for extra protection.
  • Cells contain a looped single chromosome and no nucleus.
  • Some bacteria can swim as they can be propelled by flagella.
  • Most bacterium cells contain plasmids which are rings of DNA.
  • Some bacteria can form chlorophyll so can photosynthesise but most feed off other organisms.
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  • Viruses are parasites.
  • They can only reproduce inside living cells.
  • Viruses are not made of cells. They are made of genetic material surrounded by a coat of protein.
  • Viruses do not feed, respire, excrete, move, grow or respond to their environment.
  • Many human diseases are caused by viruses.
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