Life 21- Evidence and Mechanisms of Evolution

Question 1

Genetic drift

Answer 1

Changes in gene frequencies from generation to generation as a result of random (chance) processes.

Question 2

Hardy-Weinberg equilibrium

Answer 2

In a sexually reproducing population, the allele frequency at a given locus that is not being acted on by agents of evolution: the conditions that would result in no evolution in a population.

Question 3

Sexual selection

Answer 3

Selection by one sex of characteristics in individuals of the opposite sex. Also, the favouring of characteristics in one sex as a result of competition among individuals of that sex for mates.

Question 4

Heritable trait

Answer 4

A trait that is at least partly determined by genes.

Question 5

Frequency-dependent selection

Answer 5

Selection that changes in intensity with the proportion of individuals in a population having the trait

Question 6

Artificial selection

Answer 6

The selection by plant and animal breeders of individuals with certain desirable traits.

Question 7

Genetic structure

Answer 7

The frequencies of different alleles at each locus and the frequencies of different genotype a in a Medellan population.

Question 8

Mutation

Answer 8

A change in the genetic material not caused by recombination.

Question 9

Gene pool

Answer 9

All of the different alleles of all of the genes existing in all individuals of a population.

Question 10

Population

Answer 10

Any group of organisms coexisting at the same time and in the same place and capable of interbreeding with one another.

Question 11

Gene flow

Answer 11

Exchange of genes between populations through migration of individuals of movements of gametes

Question 12

Natural selection

Answer 12

The differential contribution of offspring to the next generation by various genetic types belonging to the same population. The mechanism of evolution proposed by Charles Darwin.

Question 13

Fitness

Answer 13

The contribution of a genotype of phenotype to the genetic composition of subsequent generations, relative to the contribution of other genotype so or phenotypes.

Question 14

Stabilising selection

Answer 14

Selection against the extreme phenotypes in a population, so that the intermediate types are favoured.

Question 15

Population bottleneck

Answer 15

A period during which only a few individuals of a normally large population survive.

Question 16

Allele

Answer 16

The alternate form of a genetic character found at a given locus on a chromosome.

Question 17

Directional selection

Answer 17

Selection in which phenotypes at one extreme of the population distribution are favoured.

Question 18

Founder effect

Answer 18

Random changes in allele frequencies resulting from establishment of a population by a very small number of individuals.

Question 19

Adaptation

Answer 19

(1) In evolutionary biology, a particular structure, physiological process, or behaviour that makes an organism better able to survive and reproduce. Also, the evolutionary process that leads to the development or persistence of such a trait.
(2) In sensory neurophysiology, a sensory cell’s loss of sensitivity as a result of repeated stimulation.

Question 20

Disruptive Selection

Answer 20

Selection in which phenotypes at both extremes of the population distribution are favoured.

Question 21

Neutral allele

Answer 21

An allele that does not alter the functioning of the proteins for which it codes.

Question 22

Clinal variation

Answer 22

Gradual change in the phenotype of a species over a geographic gradient.

Question 23

Trade-off

Answer 23

The relationship between the fitness benefits conferred by an adaptation and the fitness costs it imposes. For an adaptation to be favoured by natural selection, the benefits must exceed the costs.