Biology: Chapter 2 Brief notes on Chapter 2: The Variety of Living Organisms 2.0 / 5 based on 1 rating ? BiologyGCSEAll boards Created by: Olive d(>w<)bCreated on: 10-04-12 15:15 Animals 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. 1 of 6 Plants 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. 2 of 6 Fungi 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. 3 of 6 Protoctists 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). 4 of 6 Bacteria 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. 5 of 6 Viruses 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. 6 of 6
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