Organismal biology chap 20
Mating in which a phenotypeically similar individuals mate.
Assortive mating
When the enviroment changes from year to year and different phenotypes have different fitness in different enviroments. A. natural selection will operate in a frequency-dependent manner. B. the effects of natural selection may oscillate from year to year, favoring alternative phenotypes in different years. C. genetic variation is not required to get evolutionary change by natural selection. D. None of the choices is correct.
B
Offspring were expected to be phenotypically intermediate relative to their parents.
Blending inheritance
Gene flow may promote or constrain _____ ______.
Evolutionary change
Is the movement of alleles from one population to another.
Gene flow
These subtler movements include the drifting of gametes or immature stages of plants or marine animals from one place to another. What is this an example of?
Gene flow
Changes that individuals acquired during their lives were passed on to their offspring.
Inheritance of acquired characteristics
Inbreeding is the most common form. It does not alter allele frequency but reduces the portion of heterozygotes. Which of the five agents of evolutionary change.
Nonrandom mating
Mutation and genetic drift may counter _____.
Selection
Natural selection, by favoring individuals with certain alleles, can lead to change in such ______ _______, but is not the only process that can do so.
Allele frequencies
A breeder selects for the desired characteristics.
Artificial selection
Because phenotypically similar individuals are likely to be genetically similar and thus are also more likely to produce offspring with two copies of the same allele, __________ mating will increase the proportion of homozygotes in the next generation.
Assortive mating
Gene flow can spread a ______ ______ that arises in one population to other populations.
Beneficial mutation
When selection acts to eliminate one extreme from an array of phenotypes, the genes promoting this extreme become less frequent in the population and may eventually dissapear. This form of selection is called?
Directional selection
Mating in which phenotypically different individuals mate, produces an excess of heterozygotes.
Disaddortative mating
In some situations, selection acts to eliminate intermediate types.
Disruptive selection
Gene interactions affect ______ of alleles.
Fitness
The number of surviving offspring left in the next generation.
Fitness
_______ is a combination of survival, mating success, and number of offspring per mating.
Fitness
_______ ________ is a prerequisite for evolutionary change; without it, natural selection cannot produce evolution.
Genetic variation
In the absence of factors that alter them, the frequencies of gametes, genotypes, and phenotypes remain constant generation after generation.
Hardy-Weinberg equilibrium
1. No mutation takes place 2. No genes are transferred to or form other sourcess (no immigration or emigration takes place) 3. Mating is random (individuals do not choose mates based on their phenotype or genotype). 4. The population size is very large 5. No selection occurs
Hardy-Weinberg principle
When selection acts to eliminate one extreme from an array of phenotypes, the genes promoting this extreme become_____ frequent in the population and may eventually dissapear.
Less
Are founder effects rare in nature?
No
The only agent that produces adaptive evolutionary changes. Which of the five agents of evolutionary change is this?
Selection
The best documented example of heterozygote advantage is?
Sickle cell anemia
What selection favors individuals with intermediate phenotypes?
Stabilizing selection
Genetic drift is particularly likely in populations that were founded by a ______ idividuals or in which the population was reduced to a very small number at some time in the past.
few
There are _____ agents that can lead to evolutionary change in populations.
five
Many of the most dramatic documented instances of adaptation involve _____ ______ that decrease the probability of capture by a predator.
genetic changes
Individuals with certain genotypes sometimes mate one another more commonly than would be expected on a random basis. This is known as?
nonrandom mating
In _____ populations, frequencies of particular alleles may change drastically by chance alone.
small
Evolution by natural selection occurs when the following conditions are met:
1. Phenotypic variation must exist among individuals in a population 2. Variation among individuals must result in differences in the number of offspring surviving in the next generation. 3. Phenotypic variation must have a genetic basis
Assortative mating A. affects genotype frequencies expected under Hardy-Weinberg equilibrium B. affects allele frequencies expected under Hardy-Weinberg equilibrium C. has no effect on the genotypic frequencies expected under Hardy-Weinberg equilibrium because it does not affect the relative proportion of alleles in a population. D. increases the frequency of heterozygous individuals above Hardy-Weinberg expectations.
A
Relative fitness A. refers to the survival rate of one phenotype compared to that of another B. is the physical condition of an individual's siblings and cousins C. refers to the reproductive success of a phenotype D. None of the choices is correct
A
Stabilizing selection differs from directional selection because A. in the former, phenotypic variation is reduced but the average phenotype stays the same, whereas in the latter both are variation and the mean phenotype change. B. the former requires genetic variation, but the latter does not. C. intermediate phenotypes are favored in directional selection D. None of the choices is correct.
A
What type of mating does not change the frequency of the individual alleles because it does not change the reproductive success of individuals, but rather changes with whom they mate?
Assortive mating
What type of mating is a type of nonrandom mating that causes the frequencies of particular genotypes to differ greatly from those predicted by the Hardy-Weinberg principle?
Assortive mating
Even if organisms do not move from place to place, occasionally their populations may be drastically reduced in size. This may result from flooding, drought, epidemic disease, and other natural forces, or from changes in the environment. The few surviving individuals may constitute a random genetic sample of the original population (unless some individuals survive sepcifically because of their genetic makeup). The resulting alterations and loss of genetic variability have been termed the ?
Bottleneck effect
For natural selection to result in evolutionary change A. variation must exist in a population B. reproductive success of different phenotypes must differ C. variation must be inherited from one generation to the next D. All of the choices are correct
D
Founder effects and bottlenecks are A. expected only in large populations B. mechanisms that increase genetic variation in a population C. two different modes of natural selection D. forms of genetic drift
D
Genetic drift and natural selection can both lead to rapid rates of evolution. However, A. genetic drift works fastest in large populations B. only drift leads to adaptation C. natural selection requires genetic drift to produce new variation in populations D. both processes of evolution can be slowed by gene flow
D
In a population of red (dominant allele) or white flowers in Hardy-Weinberg equilibrium, the frequency of red flowers is 91%. What is the frequency of the red allele? A. 9% B. 30% C. 91% D. 70%
D
Many factors can limit the ability of natural selection to cause evolutionary change, including A. a conflict between reproduction and survival as seen in Trinidadian guppies B. lack of genetic variation C. Pleiotropy D. All of the choices are correct
D
Suppose that the relationship between birth weight and infant mortality, instead of being at a minimum at intermediate sizes, changes such that babies born at 5 or 10 pounds had the highest survival, with a valley in between such that 7.5-pound babies had low survival rate. How would you expect the distribution of birth weights to change over time? A. It would not change B. The distribution would shift to the right C. The distribution would become bimodal, with two peaks and the mean value unchanged D. The distribution would become bimodal, with two peaks and the mean value shifted to the right.
D
Natural selection or genetically based variation leads to evolutionary change.
Darwin's theory
What selection occurs in nature when the environment changes, favoring traits at one end of the phenotypic distribution?
Directional selection
What can result from any process that causes a change in the genetic composition of a population?
Evolution
Hardy-Weinberg predictions can be applied to data to find evidence of ________ _______.
Evolutionary process
Many self-pollinating plants start new populations from a single seed. What is this an example of?
Founder effect
Sometimes one or a few individuals disperse and become the founder of a new, isolated population at some distance from their place of origin. These pioneers are not likely to carry all the alleles present in the source population. Thus, some alleles may be lost from the new population, and others may change drastically in frequency. In some cases, previously rare alleles in the source population may be a significant fraction of the new population's genetic endowment. This phenomenon is called?
Founder effect
One way to monitor how populations change over time is to look at changes in __________ of _______ of a gene from one generation to the next.
Frequencies of alleles
This type of selection favors certain phenotypes depending on how commonly or uncommonly they occur.
Frequency dependent selection
A very potent agent of change. Individuals or gametes move from one population to another. Which of the five agents of evolutionary change is this?
Gene flow
When an animal physically moves from one place to another. If the characteristics of the newly arrived individual differ from those animals already there, and if the new comer is adapted well enough to the new area to survive and mate successfully, the genetic composition of the receiving population may be altered. This is an explanation of?
Gene flow
Evolution requires ____ ____.
Genetic Variation
In small populations, frequencies of particular alleles may change drastically by chance alone. Some changes in allele frequencies occur randomly, as if the frequencies were drifting from their values. These changes are known as
Genetic drift
Statistical accidents. The random fluctuation in allele frequencies increases as population size decreases. Which of the five agents of evolutionary change is this?
Genetic drift
The effect of natural selection also may be countered by _____ _____.
Genetic drift
______ ______ can lead to the loss of alleles in isolated populations.
Genetic drift
Acquired variation is passed on to descendants.
Lamarck's Theory
The ultimate source of variation. Individual mutations occur so rarely that mutation alone usually does not change allele frequency much. Which of the five agents of evolutionary change is this?
Mutation
______ is the ultimate source of genetic variation and thus makes evolution possible.
Mutation
What generally contain considerable amounts of genetic variation?
Natural populations
Darwin proposed __________ as the mechanism of evolution.
Natural selection
Enviromental conditions determine which individuals in a population produce the most offspring.
Natural selection
Guppy color variation in different enviroments suggests ______ _____ at work.
Natural selection
Mutation rates are rarely high enough to counter the affects of ______ ______.
Natural selection
What occurs when individuals carrying certain alleles leave more offspring than those without alleles?
Natural selection
Rare phenotypes are favored by selection-thus, fitness has a negative relationship with phenotype frequencing.
Negative frequency-dependent selection
Was Darwin the first to propose a theory of evolution?
No
In some cases, selection favors one phenotype at one time and another phenotype at another time.
Oscillating selection
In what type of selection, the favored phenotype changes as the enviroment changes.
Oscillating selection
By favoring common forms, it tends to eliminate variation from a population.
Positive frequency-dependent selection
One of the most useful tools, both for generic mapping and for the analysis of population-level variation has been what ?
Single-nucleotide polymorphisms
What are defined as single-base differences between individuals that exist in the population at more than 1%?
Single-nucleotide polymorphisms
When selection acts to eliminate both extreames from an array of phenotypes, the result is to increase the frequency of the already common intermediate type. This form of selection is called?
Stabilizing selection
As genomes are sequenced more thoroughly, more and more _______ is being found.
Variation
The result of evolution driven by natural selection is that populations become better _________
adapted to their environment
Gene flow can be either a ________ or a ________ force.
constructive, constraining
In small populations, frequencies of particular alleles may change drastically by chance alone. Some changes in allele frequencies occur randomly, as if the frequencies were drifting from their values. These changes are known as genetic drift. For this reason, a population must be large to be in Hardy Weinberg Equilibrium: The smaller the population, the ______ change in allele frequenceis from generation to genertion as a result of genetic drift.
greater
Allele frequencies can also change when ______ blank bring alleles into a population.
migrants
Selection does not change the ______ ______ phenotype of the population, but rather makes it even more common by eliminating the extreames.
most common
Allele frequencies can change when ____ occur repeatedly, changing one allele to another.
mutations
Selection is a _________ process that operates to increase the representation of alleles that enhance survival and reproductive success, whereas ________ _______ is a random process in which any allele may increase.
nonrandom, genetic drift
Anytime a population becomes drastically reduced in numbers, such as in endangered species, the bottleneck effect is a _______ ________.
potential problem
The Hardy-Weinberg principle allows _______ of genotype frequencies.
prediction
The most fit phenotype is the one that
produces the greatest number of offspring
