Variation & Natural Selection (Cambridge (CIE) IGCSE Co-ordinated Sciences (Double Award): Biology): Flashcards
Exam code: 0654 & 0973
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Variation
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Cards in this collection (16)
Variation
The differences between individuals of the same species.
What is the difference between continuous and discontinuous variation?
Continuous variation: a range of values with no distinct categories (e.g. height, mass).
Discontinuous variation: distinct categories with no in-between values (e.g. blood group, tongue rolling).
Mutation
A random change in the base sequence of DNA (a gene).
Why are mutations important for variation?
A mutation is a change in DNA that can form a new allele, which is the source of genetic variation.
variation shows a range of values, such as height.
Continuous
A is a random change in the DNA base sequence.
mutation
Describe the process of natural selection.
There is variation within a population.
Organisms with advantageous features are more likely to survive (survival of the fittest).
They reproduce and pass on the advantageous alleles.
Over many generations, these alleles become more common.
Natural selection is sometimes called 'survival of the '.
fittest
within a population provides the raw material for natural selection.
Variation
What does natural selection lead to over many generations (Extended)?
Populations that are increasingly well adapted to their environment.
Explain how antibiotic resistance develops by natural selection (Extended).
Some bacteria have a mutation that makes them resistant.
When antibiotics are used, the non-resistant bacteria die but resistant ones survive.
The resistant bacteria reproduce, so resistance spreads through the population.
Selective breeding (artificial selection)
When humans choose organisms with desired features to breed together, over many generations.
Describe the process of selective breeding.
Choose parents with the desired characteristics.
Breed them together.
Select the offspring with the best characteristics.
Repeat over many generations.
Give examples of selective breeding.
Cows that produce more milk.
Crops with a higher yield.
Dogs bred for particular traits.
In selective breeding, humans choose which organisms together.
breed
What is the key difference between natural and artificial selection?
In natural selection, the environment selects which organisms survive and breed.
In artificial selection, humans choose which organisms breed.
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