VariationCambridge IGCSE Biology: Flashcards

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Define variation in the context of biology.

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Define variation in the context of biology.: Variation is the differences between individuals of the same species.
What is continuous variation? Give two examples.: Continuous variation results in a range of phenotypes between two extremes with no distinct categories. Examples include body length and body mass.
What is discontinuous variation? Give two examples.: Discontinuous variation results in a limited number of distinct phenotypes with no intermediates between them. Examples include ABO blood groups and seed shape in peas.
What causes continuous variation?: Continuous variation is caused by both genes and the environment acting together.
What causes discontinuous variation?: Discontinuous variation is usually caused by genes only, with little or no environmental influence.
Define mutation.: Mutation is a genetic change in which new alleles are formed through a change in the DNA base sequence.
What is gene mutation?: Gene mutation is a random change in the base sequence of DNA that results in a different allele.
Name two factors that increase the rate of mutation.: Ionising radiation and certain chemicals increase the rate of mutation.
What is the relationship between mutation and alleles?: Mutation is the process by which new alleles are formed through changes in the DNA base sequence.
List four sources of genetic variation in populations.: The four sources of genetic variation in populations are: mutation, meiosis, random mating, and random fertilisation.
Explain how meiosis contributes to genetic variation in populations.: Meiosis produces gametes with different combinations of alleles through crossing over and independent assortment, creating genetic variation.
How do random mating and random fertilisation contribute to genetic variation?: Random mating and random fertilisation ensure that gametes combine unpredictably, creating new combinations of alleles in offspring and increasing genetic variation.
Why is mutation described as 'random'?: Mutation is random because the change in the DNA base sequence occurs unpredictably and is not directed by the organism's needs.
Distinguish between continuous and discontinuous variation in terms of number of phenotypes.: Continuous variation produces a range of phenotypes between two extremes, whilst discontinuous variation produces a limited number of distinct phenotypes.
What is the main difference between genetic and environmental causes of variation?: Genetic causes (such as different alleles) are inherited and passed to offspring, whilst environmental causes (such as diet or climate) are not inherited and vary during an organism's lifetime.