Week 4- Quizzes, Animations, Clicker Questions Flashcards
All the alleles present in all individuals in a species are referred to as the _____ of that species.
gene pool
genotype frequency
genotype
phenotype
allele frequency
gene pool
Why: A gene pool represents all alleles in a given species in any given individual.
Genetic variation has two sources–mutation and:
recombination.
non-random mating.
genetic drift.
cell division.
natural selection.
recombination
Why: When mutations occur it allows new pairings of nucleotide base pairs. If a T is added instead of a G then there is recombination possible for pairs that receive the the T as it was not a possible pair before the mutation. Thus increasing genetic variation because it is different from the rest.
What is the result of a mutation that occurs in somatic cells?
The mutation will prevent all reproduction.
The mutation will be passed along to the organism’s offspring.
The mutation may be expressed in the individual, but will not be passed along to its offspring.
There will never be any visible effect.
The mutation will be deleterious.
The mutation may be expressed in the individual, but will not be passed along to its offspring.
Why: Germ-line mutations affect the individual and also is passed along to the offspring. Somatic cells when there is a mutation affect the individual and is not passed to the next generation because somatic cells are nonreproductive cells.
As a population geneticist, you find a species of snails with more genetic diversity than humans. What does this mean?
There is not enough information provided to answer this question.
There is more variety in the gene pool of snails than humans.
The snails have more genes on their chromosomes than humans.
The snails have more mutations occurring than humans.
The snails have more DNA than humans.
There is more variety in the gene pool of snails than humans.
Why: A Gene pool is all the alleles present in all individuals in a given population, and genetic variation is the differences in genotypes among individuals in a population. So the more variety in the gene pool the more differences in genotype hence more genetic variation.
Consider a population of killer whales. The gene pool of this population would only contain alleles harboring beneficial or neutral mutations, as deleterious mutations are efficiently eliminated from the gene pool of a species.
False
True
False
Why: Deleterious mutations may take some time to leave the gene pool there is no efficient and quick way to eliminate it but eventually it will be weeded out if it decreases survival.
In a given population, all humans have the same blood type O. If no other alleles for blood type exist in this population, this population if “fixed” for the O allele.
True
False
True
Why: For blood type O you need to have the genotype OO meaning the allele frequency for O is 100% because it is the only allele available in the population.
If a gene has two alleles, and alleles A has a frequency of 83%, then allele a has a frequency of:
17%
7%
41.5%
166%
117%
17%
Why: If allele A is 83% then to find the allele frequency for a you take the known allele and subtract it from 100%.
100% - 83% = 17%
total - allele A% = allele a%
Why can’t we measure genetic variation in a population using observable traits (phenotypes)? (Select all that apply.)
All traits are encoded by a single gene.
The environment can also affect the phenotype.
Many traits are encoded by multiple genes.
Phenotypes are not determined by genes.
The environment can also affect the phenotype.
Many traits are encoded by multiple genes.
Why: Genotype and environment make up the phenotype and trait are usually determined by more than one gene.
In a fish species the eggs tend to be fertilized more often by the mid-sized males and less often by the largest and smallest males. This is an example of:
A., stabilizing selection.
B., directional selection.
C., disruptive selection.
D., None of the other answer options is correct.
A., stabilizing selection.
Why: Stabilizing selection favors the average/ intermediate of the the two extremes. So by favoring the middle trait it is stabilizing the trend of survival.
So medium sized males is better than big and small sized males.
A cattle breeder selects the largest males for breeding with the largest females. This is an example of:
A., stabilizing selection.
B., directional selection.
C., disruptive selection.
D., None of the other answer options is correct.
B., directional selection.
Why: This is directional selection because one of the extremes is favored in this case the largest size of both gender for better breeding results in offspring. By choosing the largest size, over time the trait will become larger.
Female starlings (birds) that lay clutches of four or five eggs have more surviving young than those with either larger or smaller clutches. This is an example of:
A., stabilizing selection.
B., directional selection.
C., disruptive selection.
D., None of the other answer options is correct.
A., stabilizing selection.
Why: The clutches of 4-5 is the intermediate of bigger and smaller clutches. and since the intermediate is favored the trait is stabilizing.
On Island X the plant population contains only two species. One plant species produces only very large seeds, and the other produces only small seeds. There is only one species of bird on the island, and the birds use these seeds as their only food source. Currently there is a wide range of beak sizes within the population of birds as shown in the diagram below. Small-beaked birds are better able to consume the smaller seeds, while large-beaked birds are better at consuming the larger seeds. Birds with intermediate beak size can make use of both seed sizes.
A disease is introduced to the island which kills only the plants that produce the large seeds. Consider changes in the bird population following the death of all plants that produce large seeds. Which portion(s) of the finch population will be selected against and least likely to have their genes represented in the next generations?
A., portion A only
B., portion B only
C., portion C only
D., portions A and C simultaneously
E., portions B and C simultaneously
C., portion C only
Why: Portion C represents the birds with large beak sizes and they only eat the plant with the large seeds. Once there are no large seeded plants left the large beaked birds will die off with out the only food source and will not likely be shown in the next generation.
What type of selection occurs when an environmental condition, for example food source characteristics, causes selection toward one extreme of a trait’s range of variation?
A., stabilizing
B., directional
C., disruptive
B. directional
Why: Directional selection is when one extreme is favored so over time the trait will change in that direction of the favored extreme.
On Island X the plant population contains only two species. One plant species produces only very large seeds, and the other produces only small seeds. A rare storm blows in a flock of birds of a species never before found on the island. Within this flock there is a wide range of beak sizes as shown in the diagram here.
As their only food source, the birds find the plant seeds quite delectable. However, while small-beaked birds do very well consuming the smaller seeds, and large-beaked birds thrive on the larger seeds, birds with intermediate beak size are not good at consuming either size seed, and they struggle to get sufficient nutrition. What type of selection might we predict over the course of multiple generations of these birds?
A. stabilizing
B. directional
C. disruptive
C. disruptive
Why: Disruptive selection favors the two extremes for a trait and selects against the intermediate in this case the mid-sized beaks. Over time the mid-sized beaks will decrease until only small and large sized beak birds inhabit the island.
Prior to the publication of Darwin’s On the Origin of Species, people thought what about species?
Species evolved at one point, but no longer changed because they were not adapted to their environment.
Species were designed already perfectly adapted to their environment.
Species changed over time as guided by a divine creator.
Species changed over time because they were not adapted to their environment.
Species were designed already perfectly adapted to their environment.
Why: It was thought that a Divine Creator had made species perfectly adapted to their environment so there was no evolving.
Which of the following is an example of stabilizing selection?
decrease in the number of birds with intermediate-sized beaks who are unable to eat large or small seeds
antibiotic resistance in bacteria
selection for average birth weight in humans
breeding dogs from wolves
selection for average birth weight in humans
Why: Average birth weight in humans represents stabilizing selection because the intermediate trait is favored and the extreme traits (large and small) are selected against.
