Unit 2 - Topic 13 - Variation and Selection Flashcards
Name two causes of variation.
Genetic factors
Environmental factors
Name two types of variation.
Continuous variation
Discontinuous variation
Name the factor(s) which affect continuous variation.
Genetic factors
Environmental factors
Name the factor(s) which affect discontinuous variation.
Genetic factors
What is continuous variation?
In continuous variation there is a gradual change in a characteristic across a population, which can be represented over a range of values.
What is discontinuous variation?
In discontinuous variation the population can be clearly divided into discrete groups or categories.
Why do identical twins often show small variations in their characteristics?
Environmental factors
Give examples of continuous variation.
Height
Mass
What graph can be used to display continuous variation?
Histogram
What graph can be used to display discontinuous variation?
Bar chart
Give examples of discontinuous variation.
Tongue rolling
ABO blood groups (A, B, AB, O)
What is normal distribution?
Normal distribution is where most individuals are around the average or mean value and relatively few are found at either extremes.
Histogram.
Continuous variation.
In continuous variation, the histogram produced will show …
Normal distribution
Name the factors which affect height.
Height is continuous variation.
Genetic factors
Environmental factors
What is natural selection?
Natural selection occurs when there is a competition for resources which creates a struggle for existence. The variation amongst the individuals in the population means that some individuals will be more adapted than others. (Variation is often caused by random genetic mutations).
Better adapted individuals survive this struggle for existence (survival of the fittest). They survive to breeding age and pass on their favourable genes to the next generation. Soon the desirable characteristics become more commonplace in the population.
