Mr Exham IGCSE - Classification
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Transcript of Mr Exham IGCSE - Classification
MAKING SENSE OF CLASSIFICATION
IGCSE Biology1.2 The Variety of Living
Organisms
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Learning Objectives• Can you describe the common features shared
by organisms within the following main groups: plants, animals, fungi, bacteria, protoctists and viruses?
• What does the term ‘pathogen’ mean?• Understand that pathogens may be fungi,
bacteria, protoctists or viruses.
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Classification• All living organisms can be classified into
groups based on certain criteria. • One of the simplest forms of classification is to
split all living things into 5 Kingdoms.• Animals, plants, fungi, protoctists and
bacteria.• We will also look at viruses which are non-
living and therefore classified separately.
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Classification
Plants Animals Fungi
Protoctists Bacteria Viruses
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Plants• They are multicellular.• Cells contain chloroplasts.• Carry out photosynthesis and therefore make
their own food (autotrophic).• Have cellulose cell walls.• Store sugar as starch.
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Animals• They are multicellular.• Get their nutrition from feeding on other
organisms (heterotrophic).• They are capable of movement.• Store sugar as glycogen.
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Fungi• Can be multicellular or unicellular.• Cell wall made of CHITIN.• Made of a network of fibres called a
MYCELIUM of HYPHAE.• Feed by SAPROPHYTIC nutrition using
EXTRACELLULAR enzymes.
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Protoctists• A strange collection of simple organisms that
do not fit into the other groups therefore often known as the ‘dustbin’ kingdom.
• Mostly single celled.• E.g. protozoa like amoeba or Algae.
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Bacteria (Prokaryotes)• Small single celled organisms.• Three basic shapes: spheres, rods and spirals.• Cell wall made of polysaccharides and
proteins (peptidoglycan).• Some have a capsule or slime layer.• Has no nucleus.• Some species have flagella.• Some contain plasmids (loops of DNA) which
we can use in genetic engineering.
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Bacteria
A typical bacteria
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Viruses• All are parasites.• Much smaller than bacteria cells.• Not made of cells, and do not carry out any of
the normal ‘characteristics’ of living organisms.
• Made of genetic material surrounded by a protein coat.
• All natural viruses cause disease.
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What is a pathogen?
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What is a pathogen?
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A pathogen is an organism that causes
disease.
Pathogens• It could be a virus e.g. influenza.
• It could be a fungus e.g. athlete’s foot
• It could be a bacteria e.g. cholera
• It could be a protoctists e.g. malaria
• These pathogens can often be passed from person to person.
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