Bio - Chapter 12

Question 1

Sources of variation in traits almond individuals of a species

Answer 1

Mutation: source of new alleles
Crossing at meiosis 1 : introduces new combinations of alleles into chromosomes
Independent assortment at meiosis 1 : mixes maternal and paternal chromosomes
Fertilization : combines alleles from two parents
Changes in chromosome number or structure: often dramatic changes in structure and function.

Question 2

Gene pool

Answer 2

All of the genes in a population

Question 3

Genetic equilibrium

Answer 3

Theoretical state in which a population is not evolving (allele frequencies does not change)

Question 4

Genetic equilibrium happens when

Answer 4

Mutation never occur
Population is infinitely large
Population is isolated from gene flow
Mating is random
All individuals survive and reproduce equally

Question 5

Modes of natural selection

Answer 5

• Influences allele frequency in a population by operation in phenotype with a heritable genetic basis 
Types:
Directional selection
Stabilizing selection
Disruptive selection

Question 6

Directional selection

Answer 6

Mode of natural selection in which phenotype at one end of a range of variation are favored.
Allele frequencies shift in a consistent direction in response to selection pressure

Question 7

Stabilizing selection

Answer 7

Mode of natural select in which intermediate phenotype are favored and extreme forms are eliminated

Question 8

Disruptive selection

Answer 8

Mode of natural selection that favors extreme phenotype a in a range of variation
Intermediate forms are selected against
May lead to a new species formation

Question 9

Sexual selection

Answer 9

Some individuals of a population outreproduce others because they are at securing mates
The most adaptive forces of a trait are those that help individuals defeat rivals for mates or are most attractive to the opposite sex
Sexual dimorphism is one outcome

Question 10

Balanced polymorphism

Answer 10

Nonidentical alleles for a trait are maintained in a population
Occurs when environmental conditions favor heterozygotes over homozygotes

Question 11

Genetic drift

Answer 11

Random change in allele frequencies in a population over time, due to chance alone
Effect is greatest in small populations
Can lead to the loss of genetic diversity
•Genetic drift is pronounced in small or inbreeding populations such as those that occur after an evolutionary bottleneck

Question 12

Bottleneck

Answer 12

Reduction in population size so severe that it reduces genetic diversity
A bottleneck can lead to the founder effect

Question 13

Founder effect

Answer 13

Change in allele frequencies that occurs after a small number of individuals establish a population
Founding populations are often necessarily Inbred

Question 14

Gene flow

Answer 14

The physical movement of alleles into and out of a population, as by individuals that immigrate or emigrate
Counters the effects of mutation, natural selection, and genetic drift in a population

Question 15

Gene pool facts

Answer 15

Individuals in a population share same traits (phenotype) same genes (genotype)
Mutation create alleles
Alleles are the main source of variation in a population.
Traits with two distinct forms (dimorphic)
Traits with several district forms (polymorphic)
Traits with continuous variations interacted with the environment or several genes