Chapter 23

Question 1

Micro evolution

Answer 1

A change in allele frequency in a population over generation

Question 2

Genetic variation

Answer 2

Differences among individuals in composition of their genes or other DNA sequence

Question 3

Gene locus role in variation

Answer 3

Characters that vary in this way are typically determined by a single gene locus, with different alleles producing distinct phenotypes.

Question 4

Sources of genetic variation

Answer 4

1-when mutation, gene duplication, or other processes pro- duce new alleles and new genes
2-Sexual reproduction can also result in genetic variation as existing genes are arranged in new ways.

Question 5

Formation of allele

Answer 5

In multicellular organisms, only mutations in cell lines that produce gametes can be passed to offspring. In plants and fungi, this is not as limiting as it may sound, since many different cell lines can produce gametes

Question 6

Neutral mutation

Answer 6

Differences in DNA sequence that do-not counter the selective advantage disadvantage and occur due to point mutation in non-coding regions. It will have no affect on protein formed

Question 7

Rapid reproduction

Answer 7

-Mutation rates tend to be low in plants and animals but reproduction rate is high. so mutations can quickly generate genetic variation in populations of these organisms.

Question 8

Sexual reproduction

Answer 8

organisms that reproduce sexually, most of the genetic variation in a population results from the unique combination of alleles that each individual receives. Mechanism like crossing over, independent assortment and fertilisation causes variation

Question 9

Population

Answer 9

A group of individuals of the same species that live in the same area and interbreed

Question 10

Gene pool

Answer 10

Consist of all copies of every type of allele at every locus in all member of the population. Allele is said to be fix in a gene pool.

Question 11

Hardy Wineberg equilibrium

Answer 11

named for the British mathematician and German physician, who independently developed this idea in 1908

Question 12

Genotype frequency equation

Answer 12

P^2+2pq+q^2=1

Question 13

Allele frequency

Answer 13

P+q=1

Question 14

Five conditions when hardy Weinberg is not met

Answer 14

1. No mutations. The gene pool is modified if mutations alter alleles or if entire genes are deleted or duplicated.
2. Random mating. If individuals mate preferentially within a subset of the population, such as their close relatives (inbreeding), random mixing of gametes does not occur, and genotype frequencies change.
3. No natural selection. Differences in the survival and reproductive success of individuals carrying different genotypes can alter allele frequencies.
4. Extremely large population size. The smaller the population, the more likely it is that allele frequencies will fluctuate by chance from one generation to the next (a process called genetic drift).
5. No gene flow. By moving alleles into or out of populations, gene flow can alter allele frequencies.

Question 15

Natural selection

Answer 15

Individuals in a population exhibit variations in their heritable traits, and those with traits that are better suited to their environment tend to produce more offspring than those with traits that are not as well suited.

Question 16

Genetic drift

Answer 16

A process called genetic Chance cause allele frequencies to fluctuate unpredictably from one generation to the next, especially in small populations.

Question 17

Founder effect

Answer 17

When a few individuals become isolated from a large population, this group establishes a new population whose gene pool differs from the source population
.

Question 18

Bottle neck effect

Answer 18

A sudden change in environment such as fire or flood may drastically reduce the size of population. A sever drop in population can cause bottle neck effect (remember choke to death)

Question 19

Effect of genetic drift

-can cause harmful allele to become fix

Answer 19

• genetic drift is significant in small populations
• can cause allele frequency to change at random
• can lead to a loss of genetic variation with populations.

Question 20

Gene flow

Answer 20

-allele frequency can also change by gene flow, the transfer of allele into or out of a population due to movement of fertile individuals

Question 21

Which mechanism causes adaptation

Answer 21

Natural selection is the only mechanism that causes adaption

Question 22

Relative fitness

Answer 22

The contribution an individual makes to the gene pool of the next generation relative to the contribution of other individuals. Certain traits have greater relative fitness

Question 23

Directional selection

Answer 23

Occurs when condition favour individuals exhibiting one extreme of phenotypic range, thereby shifting a population’s frequency curve for the phenotypic character in one direction or the other.

Question 24

Distruptive selection

Answer 24

Occurs when condition favour both extreme of a phenotypic range over with intermediate phenotypes

Question 25

Stabilising selection

Answer 25

Acts against both extreme phenotypice favour intermediate variant. This mode reduces variation and tend to maintain status quo for a particular phenotypic character.

Question 26

Secual selection

Answer 26

A form of selection in which individuals with certain inherited characteristics are more likely than other individual to obtain mates. Can result in sexual dimorphism.

Question 27

Sexual dimorphism

Answer 27

A difference between two sexes in secondary sexual characteristics. Eg variation in size, colour, ornamentation and behaviour

Question 28

Intrasexual selection

Answer 28

Selection within the same sex, individuals of one sex compete directly for opposite sex

Question 29

Intersexual selection

Answer 29

Also called mate choice, individual of one sex (usually the females) are choosy in selecting their mate from other sex. In many cases depends males showiness,

Question 30

How do female preferences for certain male characteris- tics evolve in the first place?

Answer 30

One hypothesis is that females prefer male traits that are correlated with “good genes.” If the trait preferred by females is indicative of a male’s overall genetic quality

Question 31

Balancing selection

Answer 31

A selection which may preserve variation at some loci maintains two or more form of population. Selection includes heterozygous advantage and frequency dependent selections

Question 32

Heterozygote advantage

Answer 32

If individuals who are heterozygous at a particular locus have greater fitness than do both kinds of homozygote they exhibit heterozygote advantage. Natural selection tend to maintain two or more allele at a locus

Question 33

Frequency dependent selection

Answer 33

The fitness of phenotype dependent on how common it is in a population.

Question 34

Why Natural Selection Cannot Fashion Perfect Organism

Answer 34

1-selection can act only on existing variation 2-evolution is limited by historical constraints 3-adaption are often comprised 4-chance, natural selection and the environment interact. Chance event can affect subsequent evolutionary history of population.