Chapter 13: Natural Selection and Microevolution

Question 1

What is a gene pool?

Answer 1

The range of genes and all their alleles present in a population

Question 2

What can the frequency of polymorphic alleles be affected by?

Answer 2

• Mutation of an allele
• Immigration of individuals
• Emmigration of individuals
• The reproduction rate of various individuals

Question 3

What are some factors which may change an allele frequency?

Answer 3

• Genetic drift
• The bottleneck effect
• The founder effect

Question 4

What is genetic drift?

Answer 4

A change in the gene pool of a population as a result of chance; usually occurs in small populations

Question 5

What is the bottleneck effect?

Answer 5

When a catastrophic event or a period of adverse conditions drastically reduces the size of a population

Question 6

What is the founder effect?

Answer 6

A type of gene flow that occurs when a few individuals that have become isolated from a larger population do not carry all the alleles that were present in the original population

Question 7

What is gene flow?

Answer 7

The transfer of alleles that results from emigration and immigration of individuals between populations

Question 8

What are some negatives and positives of losing allele frequency in a gene pool?

Answer 8

A negative can be that the limited gene pool would create a higher risk of mutation, a positive can be that certain alleles that may cause mutations or a physical disadvantage would be lost.

Question 9

What are the few proposistions that are the priciple of natural selection leading to evolutionary change?

Answer 9

• Individuals differ from one another
• These variations are caused by mutations and are inheritable
• More offspring are born than can survive
• Some individuals have traits that make them more suited to their environment (viability), making them better to reproduce and pass on their alleles (fecundity)

Question 10

What is viability in terms of evolutionary change?

Answer 10

Capablility/suitability of living in the environment

Question 11

What is fecundity in terms of evolutionary change?

Answer 11

A measure of fertility; the capacity to reproduce

Question 12

What is fitness in terms of natural selection?

Answer 12

The capacity of an individual to survive and pass on viable offspring

Question 13

What is adaptive evolution?

Answer 13

Changes in populations of organisms that make that population better adapted to its environment over time

Question 14

What are selection pressures?

Answer 14

A factor that influences the survival of an individual within a population

Question 15

What are some selection pressures?

Answer 15

• Competition between species for food/territories
• Predator - prey relationships
• Competition within species for food or water
• Competition within species for territories or nesting places
• Sexual selection, traits that sucessfully attract mates

Question 16

What are the three types of phenotypic selection?

Answer 16

Stabilising, directional and disruptive selection (refer to figure 13.2.2 pg 249 for graphs)

Question 17

What is stabilising selection?

Answer 17

A form of selection that tends to advantage organisms similar to their parents; this usually occurs when the environment is very stable and unchanging and selects against extremes of phenotype

Question 18

What is directional selection?

Answer 18

A form of selection that selects against one of two extremes and leads to a change in a trait over time

Question 19

What is disruptive selection?

Answer 19

A form of selection that operates in favour of extremes and against intermediate forms