This is a presentation designed to help explain the section of the Edexcel IGCSE Biology course about classification in the variety of living organisms section. For more help with IGCSE Biology please visit mrexham.com

1. IGCSE Biology – 4BI0
MAKING SENSE OF
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1.2 Classification– The Variety of Living Organisms
Objectives
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• 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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1.2 Classification– The Variety of Living Organisms
Classification
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• 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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1.2 Classification– The Variety of Living Organisms
Classification
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1.2 Classification– The Variety of Living Organisms
Plants
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• 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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1.2 Classification– The Variety of Living Organisms
Animals
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• 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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1.2 Classification– The Variety of Living Organisms
Fungi
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• 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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1.2 Classification– The Variety of Living Organisms
Protoctists
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• 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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1.2 Classification– The Variety of Living Organisms
Bacteria (Prokaryotes)
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• 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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1.2 Classification– The Variety of Living Organisms
Bacteria (Prokaryotes)
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A typical bacteria

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1.2 Classification– The Variety of Living Organisms
Viruses
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• 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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1.2 Classification– The Variety of Living Organisms
Pathogens
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1.2 Classification– The Variety of Living Organisms
Pathogens
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• 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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