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biology 0610printed 8 · PDF 8
328 pagesrevision 46933
printed 8 · PDF 8
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⦁ Studies of DNA sequences of different species show that the more similar the base
sequences in the DNA of two species, the more closely related those two species are (and
the more recent in time their common ancestor is)
⦁ This means that the base sequences in a mammal’s DNA are more closely related to all
other mammals than to any other vertebrate groups
⦁ As DNA base sequences are used to code for amino acid sequences in proteins, the
similarities in amino acid sequences can also be used to determine how closely related
organisms are
Dichotomous keys
⦁ These keys are used to identify organisms based on questions about their features; a
commonly occurring question in the examinations.
Features of organisms
⦁ There are 5 main kingdoms: Animalia, Plantae, Fungi, Protoctista, and Prokaryotes
Features of Animalia:
Multicellular
Cells contain a nucleus but not a cell wall or chloroplasts
They feed on organic substances made by other organisms
Features of Plantae:
Multicellular
Cells contain a nucleus, cell wall and chloroplasts
They all feed by photosynthesis and aren’t reliant on other organisms as they make
their own food
Features of Fungi:
Multicellular usually
Cells have nucleus and cell walls not made of cellulose but chitin
Feed saprophytically on dead or decayed material