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Cambridge IGCSE Biology
Classification and Keys
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You will need to be able to:
• Define and describe the binomial system of naming
species
• Use a dichotomous key to identify an unknown organism
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Biological classification:
Taxonomic
ranks
Kingdom
Animalia
Phylum
Chordata
Class
Mammalia
Order
Carnivore
Family
Felidae
Genus
Panthera
Species
pardus
Panthera pardus
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The binomial system gives organisms a two
word name showing the genus and species
Genus
species Genus
Panthera leo
species
Panthera tigris
Genus
species
Panthera pardus
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There are other classification systems:
• Cladistics:
Based on similarity and differences
between DNA and RNA sequences
AAAA
Extended
AGAA
AACA
AGTA
AGGA
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You will need to be able to:
• Define and describe the binomial system of naming
species
• Use a dichotomous key to identify an unknown organism
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Keys use a series of questions to
identify unknown organisms
cap
Identify the fungus
1. Stalk does not have a frill
Stalk has a frill
go to 2
go to 3
2. Stem is brown
Stem is yellow
Fungus A
Fungus B
3. Cap has spots
Cap does not have spots
go to 4
Fungus C
4. Cap is red
Cap is brown
Fungus D
Fungus E
frill
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Now you should be able to
• Define and describe the
binomial system of naming
species
• Use a dichotomous key to
identify an unknown
organism
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Cambridge IGCSE Biology
www.ClickBiology.com
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