Chapter 19

Question 1

Nature selects particular individuals. Acts on individuals but ONLY populations evolve

Answer 1

natural selection

Question 2

group of members of the same species

Answer 2

population

Question 3

The sum of all alleles in a population

Answer 3

gene pool

Question 4

Hardy Weinberg allele equation:

Answer 4

p+q=1

Question 5

Hardy Weinberg genotypes equation:

Answer 5

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

Question 6

p in Allele Weinberg equations stand for what?

Answer 6

dominant allele (p=A)

Question 7

q in Allele Weinberg equations stand for what?

Answer 7

recessive allele (q=a)

Question 8

p^2 in Genotypes equation stands for what?

Answer 8

homozygous dominant (AA)

Question 9

2pq in Genotypes equation stands for what?

Answer 9

heterozygous (Aa)

Question 10

q^2 in Genotypes equation stands for what?

Answer 10

homozygous recessive (aa)

Question 11

Answer the equation for the Allele Weinberg equation:
What does q equal?
p=A= .9
q=???

What about finding p?
p=???
q= 0.2

Answer 11

q(a)= .1, p(A)= 0.8

Question 12

New alleles arise by this, a change in the nucleotide sequence of DNA. Only these in cells that produce gametes can be passed to offspring.

Answer 12

mutation

Question 13

A change of a single nucleotide in a DNA sequence.

Answer 13

“point mutation”

Question 14

The rate at which a specific allele appears within a population. ex.)ABO Blood

Answer 14

Allele frequency

Question 15

3 main mechanisms cause allele frequency change:

Answer 15

• Natural Selection
• Genetic Drift
• Gene Flow

Question 16

A population’s individuals often display different phenotypes, or express different alleles of a particular gene, which is referred to as this.

Answer 16

polymorphisms

Question 17

Populations with 2 or more variations of a particular characteristic

Answer 17

polymorphic

Question 18

The fraction of phenotype variation that we can attribute to genetic differences, or genetic variability, among individuals in a population. The greater this is of a population phenotypic variation, the more susceptible it is to the evolutionary forces that act on heritable variation.

Answer 18

Heritability

Question 19

The diversity of alleles and genotypes within a population. When scientists are involved in the interbreeding of species, such as with animals in zoos and nature preserves, they try to increase this variability to preserve as much as the phenotypic diversity as possible. This also reduces associated risks of interbreeding.

Answer 19

genetic variability

Question 20

the mating of closely related individuals, which can have the undesirable effect of bringing together deleterious recessive mutations that can cause abnormalities and susceptibility to disease.

Answer 20

interbreeding

Question 21

What are the 5 things involved in natural selection:

Answer 21

1.) Directional Selection
2.) Disruptive Selection
3.) Stabilizing Selection
4.) Balancing Selection
5.) Sexual Selection
a.) intrasexual selection
b.) intersexual selection

Question 22

What are the 2 things apart of Genetic Drift?

Answer 22

1.) founder effect
2.) bottleneck effect

Question 23

Choose individuals at 1 end of the phenotypic range are selected.
far left o far right. Selects for phenotypes at one end of the spectrum of existing variation. When environment changes, population will undergo this. Th result of this type of selection is a shift in population genetic variability, towards the new, fit phenotype.
ex.) begins far left when there are more tan mice. However, dark brown coloration arises by a new mutation. Dark brown fur makes the mouse less susceptible to predation. The population of dark mice has a higher mean fitness than the starting population of tan mice and so have a higher chance of survival and ability to grow and reproduce, so, now the population is skewed to the far right due to this form of selection.
ex.) Peppered moth. Prior to Industrial Evolution, the moths were light in color, which allowed them to blend in with light-colored trees and lichens in their environment. However, as soot began spewing from factories, the trees darkened and so did the moths. Light-colored moths became easier to spot by predatory birds. Overtime, darker moths form increased and then had a higher survival rate in habitats with air pollution because they blended in.

Answer 23

Directional Selection

Question 24

Chosen are 2 or more phenotypes. 2 or more distinct phenotypes can each have their advantages for natural selection, while the intermediate phenotypes are, on average, less fit. Occurs when conditions favor individuals at both extremes of the phenotypic range.
Ex.) Large, dominant alpha males use brute force to obtain mates, while small males can sneak in for furtive copulations with the females in an alpha male’s territory. In this case, both the alpha males and the “sneaking” males will be selected for, but medium-sized males, who can’t overtake the alpha males and are too big to sneak copulations, are selected against.
Ex.) Imagine a mouse population living at the beach where there is light-colored sand interspersed with patches of tall grass. In this scenario, light-colored mice that blend in with the sand would be favored, as well as dark-colored mice that can hide in the grass. Medium-colored mice, alternatively would not blend in with either the grass or the sand, and thus predators would most likely eat them. The result of this type of selection is increased genetic variability as the population becomes more diverse.

Answer 24

Disruptive Selection

Question 25

Where middle phenotype is selected. Occurs when conditions favor immediate variants and act against extreme phenotypes. If natural selection favors on average phenotypes, selecting against extreme variation, the population will undergo this. 1 egg is to little, 7 is too much, but 4 eggs is just right.
ex.) in a mouse population that live in the woods, for example, natural selection is likely to favor mice that best blend in with the forest floor and are less likely for predators to spot. Assuming the ground is a fairly consistent shade of brown, those mice whose fur is most closely matched to that color will be most likely to survive and reproduce, passing on their genes for their brown coat. Mice that carry alleles that make them a bit lighter or a bit darker will stand out against the ground and be more likely to fall victim to predation. As a result of this selection, the population’s genetic variability will decrease.

Answer 25

Stabilizing Selection

Question 26

Where 2 or more phenotypes are kept in a population. Occurs when natural selection maintains stable frequencies of 2 or more phenotypic forms in a population.

Answer 26

Balancing Selection

Question 27

What are the two types of balancing selections?

Answer 27

• heterozygous advantage
• frequency-dependent selection

Question 28

Heterozygous has an advantage. Heterozygotes have higher fitness than homozygotes. Natural selection will tend to maintain two or more alleles at that locus
ex.) The sickle cell allele causes deleterious mutations in hemoglobin but also confers malaria resistance.
SICKLE CELL ANEMIA
AA= good no sickle cell
Aa= good no sickle cell
aa= bad, sickle cell
Malaria -
AA: yes you have it
Aa: no malaria
aa: no malaria

Answer 28

Heterozygous advantage

Question 29

Who is being selected is dependent based on how common they are. May be good to be 1 fish over the other.
ex.) We can observe an interesting example of this type of selection in a unique group of Pacific Northwest lizards. Male common side-blotched lizards come in three throat-color patterns: orange, blue, and yellow. Each of these forms has a different reproductive strategy: orange males are the strongest and can fight other males for access to their females. Blue males are medium-sized and form strong pair bonds with their mates. Yellow males are the smallest, and look a bit like females, which allows them to sneak copulations. Like a game of rock-paper-scissors, orange beats blue, blue beats yellow, and yellow beats orange in the competition for females. That is, the big, strong orange males can fight off the blue males to mate with the blue’s pair-bonded females, the blue males are successful at guarding their mates against yellow sneaker males, and the yellow males can sneak copulations from the potential mates of the large, polygynous orange males.
In this scenario, natural selection favors orange males when blue males dominate the population. Blue males will thrive when the population is mostly yellow males, and yellow males will be selected for when orange males are the most populous. As a result, populations of side-blotched lizards cycle in the distribution of these phenotypes—in one generation, orange might predominate, and then yellow males will begin to rise in frequency. Once yellow males comprise a majority of the population, blue males will be selected. Finally, when blue males become common, orange males once again will be favored. As indicated above, if the selection is against the common, favoring the rare, so in the case of the lizard there is negative frequency-dependent selection.

Answer 29

Frequency-dependent selection

Question 30

Choosing a mate to reproduce. The selection pressures on males and females to obtain mating’s. This selection can be so strong that it selects traits that are actually detrimental to the individual’s survival. Think, once again, about the peacock’s tail. While it is beautiful and the male with the largest, most colorful tail is more likely to win the female, it is not the most practical appendage. In addition to greater visibility to predators, it makes the males slower in their attempted escapes. There is some evidence that this risk is why females like the big tails in the first place.

Answer 30

Sexual selection

Question 31

Marked differences between sexes in secondary sexual characteristics. Where male and female look different from each other. Male has to attract the woman so.. Males are often larger, for example, and display many elaborate colors and adornments, like the peacock’s tail, while females tend to be smaller and duller in decoration.

Answer 31

sexual dimorphism

Question 32

Between members of the sAme sex. IS competition among individuals of one sex (often males) for mates of the opposite sex.
ex.) 2 male giraffes fighting over female giraffe

Answer 32

IntrAsecual selection

Question 33

Between members of diffErent sex. Often called mate choice, occurs when individuals of one sex (usually females) are choosy in selecting their mates.
ex.) Michael Jackson bird uses his wings to impress a different type of female bird

Answer 33

IntErsexual selection

Question 34

Change in allele frequency due to chance. Choosing individuals due to chance; who’s being selected is random. Can be either at the right place at the right time (when a receptive female walks by) or the wrong place at the wrong time (when a fox was hunting).
ex.) Natural Disasters.

Answer 34

Genetic Drift

Question 35

A few individuals found or made their own population. A few individuals become isolated from a larger population. Portion of population leaves to start a new population in a new location or physical barrier drives a population. When the genetic structure changes to match that of the new population’s founding fathers and mothers. An event that initiates an allele frequency change in an isolated part of the population, which is not typical of the original population.

Answer 35

Founder effect

Question 36

Not a lot of genetic diversity. Can result from a drastic reduction in population size due to a sudden environment change. It results in suddenly wiping out a large potion of the gene pool. By chance, the resulting gene pool may no longer be reflective of the original population gene pool. If population remains small, it may be further effected by genetic drift. A genetic drift event that can kill a lot of individuals decreasing population and diversity.
ex.) amount of panthers decreased (fur looked weird along with tails). small alleles=not enough sperm to reproduce. genes were added (by researchers) to fix it.

Answer 36

Bottleneck Effect

Question 37

Migrate; bring new individuals in population. Movement of alleles among populations. The flow of alleles in and out of population due to the migration of individuals or gametes. Alleles can be transferred through the movement of fertile individuals or gametes (ex. pollen).
ex.) humans- remember how we used to be? changed because more alleles and organisms were brought in.
ex.) plants send their pollen far and wide, by wind or bird to pollinate other population of the same species some distance away.
Pride of lions also experience immigration/emigration as developing males leave their mothers o seek out a new pride with genetically unrelated females.
This variable flow of individuals in and out of the group not only changes the population’s gene structure, but it can also introduce new genetic variation to population in different geological locations and habitats.

Answer 37

Gene Flow

Question 38

An increase in frequency of alleles that improve fitness (ability to produce offspring)

Answer 38

Adaptive Evolution

Question 39

Why natural selection cannot fashion perfect organisms:

Answer 39

• Selection can act only on existing variations
• Evolution is limited by historical constraints
• Adaptations are often compromises
• Chance, natural selection, and the environment interact

Question 40

Influence genotypes.
ex.) a gator is likely to have darker skin than a city dweller, due to regular exposure to the sun, an env. factor.
For some species, the env. determines some major characteristics, such as sex. ex.) some turtles and other reptiles have temperature dependent sex determination(TSD). TSD means that individuals develop into males if their eggs are incubated within a certain temp range, or females at a different temp range.

Answer 40

Environment Variation

Question 41

What is the difference between micro- and macroevolution?

A.) Microevolution describes the evolution of small organisms, such as insects, while macroevolution describes the evolution of large organisms, like people and elephants.
B.) Microevolution describes the evolution of microscopic entities, such as molecules and proteins, while macroevolution describes the evolution of whole organisms.
C.) Microevolution describes the evolution of organisms in populations, while macroevolution describes the evolution of species over long periods of time.
D.) Microevolution describes the evolution of organisms over their lifetimes, while macroevolution describes the evolution of organisms over multiple generations.

Answer 41

C.) Microevolution describes the evolution of organisms in populations, while macroevolution describes the evolution of species over long periods of time.

Question 42

Population genetics is the study of:
a.) how selective forces change the allele frequencies in a population over time
b.) the genetic basis of population-wide traits
c.) whether traits have a genetic basis
d.) the degree of inbreeding in a population

Answer 42

a.) how selective forces change the allele frequencies in a population over time

Question 43

Which of the following populations is not in Hardy-Weinberg equilibrium?
A.) a population with 12 homozygous recessive individuals (yy), 8 homozygous dominant individuals (YY), and 4 heterozygous individuals (Yy)
B.) a population in which the allele frequencies do not change over time
C.) p2 + 2pq + q2 = 1
D.) a population undergoing natural selection

Answer 43

D.) a population undergoing natural selection

Question 44

One of the original Amish colonies rose from a ship of colonists that came from Europe. The ship’s captain, who had polydactyly, a rare dominant trait, was one of the original colonists. Today, we see a much higher frequency of polydactyly in the Amish population. This is an example of:
A.) natural selection
B.) genetic drift
C.) founder effect
D.) b and c

Answer 44

D.) b and c

Question 45

When male lions reach sexual maturity, they leave their group in search of a new pride. This can alter the allele frequencies of the population through which of the following mechanisms?
A.) natural selection
B.) genetic drift
C.) gene flow
D.) random mating

Answer 45

C.) gene flow

Question 46

Which of the following evolutionary forces can introduce new genetic variation into a population?
A.) natural selection and genetic drift
B.) mutation and gene flow
C.) natural selection and nonrandom mating
D.) mutation and genetic drift

Answer 46

B.) mutation and gene flow

Question 47

When closely related individuals mate with each other, or inbreed, the offspring are often not as fit as the offspring of two unrelated individuals. Why?
A.) Close relatives are genetically incompatible.
B.) The DNA of close relatives reacts negatively in the offspring.
C.) Inbreeding can bring together rare, deleterious mutations that lead to harmful phenotypes.
D.) Inbreeding causes normally silent alleles to be expressed.

Answer 47

C.) Inbreeding can bring together rare, deleterious mutations that lead to harmful phenotypes.

Question 48

Describe a situation in which a population would undergo the bottleneck effect and explain what impact that would have on the population’s gene pool.

Answer 48

A hurricane kills a large percentage of a population of sand-dwelling crustaceans—only a few individuals survive. The alleles carried by those surviving individuals would represent the entire population’s gene pool. If those surviving individuals are not representative of the original population, the post-hurricane gene pool will differ from the original gene pool.

Question 49

Which type of selection results in greater genetic variance in a population?
A.) stabilizing selection
B.) directional selection
C.) diversifying/disruptive selection
D.) positive frequency-dependent selection

Answer 49

C.) diversifying/disruptive selection

Question 50

When males and females of a population look or act differently, it is referred to as ________.
a.) sexual dimorphism
b.) sexual selection
c.) diversifying selection
d.) a cline

Answer 50

a.) sexual dimorphism