The probability of extinction of a species increases if the population is small with low genetic variation.

State two processes that cause population size to decrease.

Explain how meiosis promotes variation.

a. mortality / fatal disease / predation / competition / other cause of death;
b. emigration;

a. (in prophase I) crossing over/chiasmata formation (between homologous chromosomes);
b. random alignment of homologues/bivalents in metaphase I / independent assortment of homologues / chromosomes;
c. second division of meiosis separates alleles further;
d. combinations of alleles in gametes is unlimited/2ⁿ;

Many students were able to state examples of conditions that led to increases in mortality. Better prepared candidates identified emigration as a cause of population decrease.

A surprising number could not correctly link the events of meiosis to the correct phase indicating a lack of understanding of the necessary sequence of events. Many did not recognize that the second stage of meiosis also resulted in an increase of variety.