Y12 BIOLOGY EXAM 2022 UNIT 4 AOS2

Gene flow occurs...

• ...when natural forces act on existing variation
• ...when two populations mix, but do not mate
• ...when new individuals are added to a population
• ...when a population is split

Populations do not necessarily consist of the individuals best adapted to survive and reproduce. Theoretically, the most fit individuals in a population will survive longest and reproduce the most, however chance plays a role in who survives, Reproduces, and whose offsprings survive to reproduce as well. In a population, where the allele frequency shifts by random chance, the mechanism of evolution at work is___.

• Natural selection
• Genetic drift
• Migration
• Mutation

Which of the following is not true of genetic drift?

• It results from the random transmission of alleles from parents to offspring in a population
• It can lead to alleles being fixed in a population
• It can increase the genetic diversity of a population
• It can lead to loss of alleles in a population

The bottleneck effect occurs when a population size is reduced for at least one generation. Undergoing a bottleneck can greatly reduce the genetic variation a population, leaving it susceptible to extinction if it is unable to adapt to climatic changes, or changes in resource or availability.  Small populations are especially at risk when a bottleneck occurs, caused by the greater effect ____ can have on small populations.

• Migration
• Natural selection
• Genetic drift
• Mutation

An ecologist observes a population of snakes on an island for a month every year. After the eleventh month, he sees the snake population has been decimated, and decides to wait for the snakes to repopulate before coming back for further observation. When he returns five years later, he finds a very homogenous-looking population of snakes. What is the name of the effect he observed?

• Genetic Drift
• Founder Effect
• Disaster effect
• Bottleneck effect

Refer to the illustration above. During which time period are the birth rate and death rate equal

• period 1
• period 2
• period 3
• period 4

As a population reaches its carrying capacity, there may be an increase in competition for

• food
• shelter
• mates
• all the above

Biodiversity refers to

• extinct species
• the variety of species on Earth
• nonrenewable resources
• the rate of species decline

The movement of individuals into a population

• emigration
• immigration
• dispersion
• population density

The two species, Paramecium aurelia and Paramecium caudatum, which do not prey upon each other, fighting to grow in the same test tube is an example of which of the following?

• Competition
• Predation
• Emigration
• Immigration