Mechanisms of Evolution

Question 1

Gene Pool

Answer 1

– total of all alleles within the population.
Ex. Allele for beetles colour could be green or beige

Question 2

Allele frequency

Answer 2

determines the genetic characteristics of that population.

Question 3

Microevolution

Answer 3

Changing percentages or frequencies of alleles within populations leads to evolution within a population

Question 4

Mutation: Factors that cause evolutionary change

Answer 4

Description: Mutation randomly introduces new alleles into a population
Effect: Mutation changes an alleles frequencies

Question 5

Gene Flow: Factors that cause evolutionary change

Answer 5

Description: Gene flow occurs between two different inbreeding populations that have different allele frequencies
Effect: Gene flow may change allele frequencies in either or both populations through a “flow”, or movement, of genes, (Alleles)

Question 6

Non-randoming mating: Factors that cause evolutionary change

Answer 6

Description: During non - random mating , individuals in a population select mates, often on the basis of their phenotypes
Effect: Non-random mating increases populations, but does not affect the frequencies of alleles

Question 7

Genetic drift: Factors that cause evolutionary change

Answer 7

Description: Genetic drift refers to random changes in genetic variation from generation to generation due to chance
Effect: genetic drift changes the frequencies of alleles

Question 8

Founder effect: Factors that cause evolutionary change

Answer 8

• a change in gene pool that results when a few individuals start a new isolated population
• These “founders” carry some but not all alleles from the original population’s gene pool which means diversity of new population is limited
• This is usually seen in island populations - - Ex: Amish population of Philadelphia, PA was found in 1700s by only a few families. Now the population has an unusually high frequency of polydactylism (presence of 6 th finger or toe)

Question 9

Bottle neck effect: Factors that cause evolutionary change

Answer 9

• changes in gene distribution that results from a rapid decrease in population size * Things like starvation disease and natural disasters can severely reduce the size of a population
• Survivors only have a few of the various alleles that were present before in the larger population so now the gene pool now has less diversity

Question 10

Natural selection: Factors that cause evolutionary change

Answer 10

Description: Natural selection is the result of the environment selecting for individuals in a population with certain traits that make them better suited to survive and reproduce than others in the population
Effect: Over many generations, frequencies of alleles of many different genes may change, resulting in significant changes in the characteristics of a population

Question 11

Natural Selection: Stabilizing

Answer 11

• favours an intermediate phenotype and selects against extreme variants of the phenotype
• Ex. weight of human babies

Question 12

Natural selection: Disruptive

Answer 12

• favors both extreme phenotypes over the intermediate phenotypes
• Sometimes intermediate phenotypes are completely eliminated from the population
• Ex: Male coho salmon - > Very large phenotype (4500 grams or more) are better at fighting for access to females’ eggs and very small phenotype (~ 500 grams) are better at “sneaking” & fertilizing females’ eggs.

Question 13

Natural selection: Directional

Answer 13

favors phenotype at one extreme over the other
- This type of selection is common during times of environmental change
- Ex: colour of pepper moths or antibiotic-resistant bacteria

Question 14

sexual selection

Answer 14

• type of natural selection based on competition between males and choices made by females
• Males will fight each other or use visual displays to attract the female

Question 15

sexual dimorphism

Answer 15

striking difference between males and females of the same species.