Ch. 13 Evolution

Question 1

What is evolutionary theory?

Answer 1

a scientific body of work concerned with studying the mechanisms that cause evolutionary change in populations, and the application of this knowledge to understanding biological problems

Question 2

Explain positive feedback.

Answer 2

occurs in a system when a product of the system speeds up an earlier process

Question 3

Explain negative feedback.

Answer 3

occurs when a product of a system slows down an earlier process in the system

Question 4

Explain Charles Darwin’s contributions to evolutionary theory.

Answer 4

He was the first person to articulate a theory of evolutionary change based on scientific study and observation. He found that many organisms living on the Galápagos Islands were unique from those found in any other part of the world. He also found that organisms differed from island to island, yet retained some similarities to organisms found on the South American mainland. From observations and insights made on the voyage and new ideas from geologists on the age of the Earth, Darwin developed an explanatory theory for evolutionary change: species change over time, divergent species share a common ancestor, the mechanism that produces change is natural selection.

Question 5

Explain natural selection

Answer 5

The differential survival & reproduction of individuals is due to variation of their traits. As more and more individuals of a population acquire new adaptive traits, the characteristics of the entire population evolve. Natural selection increases the frequency of beneficial mutations in populations.

Question 6

Explain adaptation.

Answer 6

the processes by which useful characteristics evolve as well as the characteristics themselves. A favored trait that spreads through a population by natural selection.

Question 7

Explain mutation

Answer 7

The origin of genetic variation is mutation.

Mutation is any change in nucleotide sequences. Mutations occur randomly with respect to an organism’s needs; natural selection acts on this random variation and results in adaptation.

To make gametes, you have to make copies of DNA. This process introduces some errors (mutations) in the new DNA. The mutation could be no change, alter the function, or alter the gene with a new gene/new function.

Question 8

What is an allele?

Answer 8

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

Question 9

What is a gene pool?

Answer 9

sum of all copies of all alleles at all loci in a population

Question 10

What is allele frequency?

Answer 10

Proportion of each allele in the gene pool. Is the measure of the amount of genetic variation in a population.

Question 11

What is genotype frequency?

Answer 11

Proportion of each genotype among individuals in the population. Show how much variation is distributed among members of the population.

Question 12

Explain genetic drift.

Answer 12

genetic drift refers to changes in allele frequencies from one generation to the next due to random sampling; affects both large and small populations.

Question 13

how do you calculate an allele’s frequency?

Answer 13

Question 14

What is gene flow?

Answer 14

migration of individuals or movement of gametes between populations results in gene flow, which can change allele frequencies. If gene flow between two populations stops, those populations may diverge and become different species.

Question 15

What is the founder effect?

Answer 15

genetic drift changes allele frequencies when a few individuals colonize a new area It is equivalent to a large population reduced by a bottleneck.

Question 16

What is nonrandom mating?

Answer 16

when individuals mate preferentially with other individuals of the same genotype (including themselves i.e. self-fertilization in plants)

Question 17

What is sexual selection?

Answer 17

Sexual selection occurs when individuals of one sex mate preferentially with particular individuals of the opposite sex rather than at random. Some seemingly nonadaptive traits may make an individual more attractive to the opposite sex. There may be a trade-off between attracting mates (more likely to reproduce) and attracting predators (less likely to survive).

Question 18

What does diploid mean?

Answer 18

it means that you have two copies of each gene, like humans

Question 19

What does haploid mean?

Answer 19

One form of each gene, like human gametes

Question 20

Explain Alfred Russel Wallace’s contributions to the factual basis of evolutionary change.

Answer 20

Wallace developed a theory on natural selection and then shared it with Darwin, which kick started Darwin’s theory of evolution. In total, Wallace’s work is very important to our understanding of variance within populations and the empirical evidence of natural selection.

Question 21

What are the four other main mechanisms other than natural selection that cause changes in the genetic structures of populations?

Answer 21

mutations, gene flow, genetic drift, and nonrandom mating

Question 22

What was Darwin’s explanatory theory for evolutionary change?

Answer 22

• species change over time
• divergent species share a common ancestor (descent with modification)
• the mechanism that produces change is natural selection

Question 23

Do individuals or populations evolve?

Answer 23

populations, members of a population become adapted to the environment in which they live

Question 24

How do you calculate allele frequencies?

Answer 24

1) Count the number of alleles: For a specific gene, count the number of copies of each allele present in the population. For diploid organisms, each individual has two alleles for a given gene.

2) Calculate the total number of alleles: Add up the counts of all alleles for that gene. This will give you the total number of alleles in the population.

3) Calculate allele frequencies: To calculate the frequency of a specific allele, divide the number of copies of that allele by the total number of alleles in the population.

p = (numbers of copies of allele A)/(total number of alleles)

q = (numbers of copies of allele B)/(total number of alleles)

Note: p + q = 1

Question 25

What is the Hardy-Weinberg equilibrium?

Answer 25

a theoretical population in which allele frequencies remain constant over generations in the absence of evolutionary forces such as mutation, migration, genetic drift, and natural selection

Question 26

What is a population bottleneck?

Answer 26

A population bottleneck refers to a large reduction in the size of a population with accompanying reduction in genetic variation.

Question 27

How do you calculate genotype frequencies?

Answer 27

We’re going to use the allele frequencies we’ve already determined and apply them to the Hardy-Weinberg equilibrium equation.

p^2 + 2pq + q^2 = 1

p^2 = frequency of the homozygous genotype for allele A (AA)

2pq = frequency of the heterozygous genotype (AB)

q^2 = frequency of the homozygous genotype for allele B (BB)

1) calculate allele frequencies for allele’s A and B

2) Use the H-E equation

3) sum the genotype frequencies, make sure all three genotypes add up to 1(100%)

Question 28

For a population to be at Hardy-Weinberg Equilibrium, what must be true?

Answer 28

there must be random mating and large population size, no mutation, no gene flow, and no selection of genotypes

Question 29

How does natural selection act on quantitative traits?

Answer 29

1) stabilizing selection favors average individuals

2) directional selection favors individuals that vary in one direction from the mean

3) disruptive selection favors individuals that vary in both directions from the mean

Question 30

What is stabilizing selection?

Answer 30

reduces variation in populations but does not change the mean

Question 31

What is directive selection?

Answer 31

Individuals at one extreme of a character distribution contribute more offspring to the next selection. For a single gene locus, directional selection may favor a particular variant–positive selection for that variant.

Question 32

What is disruptive selection?

Answer 32

Individuals at opposite extremes of a character distribution contribute more offspring to the next generation. This results in increased variation in the population, can result in a bimodal distribution of traits.

Question 33

What is the principle cause of natural selection?

Answer 33

the environment