Term
| What is a change in allele frequencies in a population over generations? |
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Definition
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Term
| What two processes produce the variation in gene pools that contributes to differences among individuals? |
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Definition
| Mutation and sexual reproduction |
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Term
| Population geneticists measure polymorphisms in a population by determining what? |
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Definition
| the amount of heterozygosity at the gene and molecular levels. |
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Term
| What measures the average percent of loci that are heterozygous in a population? |
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Definition
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Term
Nucleotide variability is measured by
comparing what? |
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Definition
the DNA sequences of pairs of
individuals. |
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Term
| What are differences between gene pools of separate populations or population subgroups? |
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Definition
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Term
What is a graded change in a trait
along a geographic axis? |
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Definition
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Term
What are changes in the nucleotide
sequence of DNA? |
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Definition
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Term
| What is a localized group of individuals capable of interbreeding and producing fertile offspring? |
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Definition
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Term
| What consists of all the alleles for all loci in a population? |
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Definition
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Term
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Definition
When all individuals in a population
are homozygous for the same allele. |
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Term
| How can the frequency of an allele in a population can be calculated? |
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Definition
-For diploid organisms, the total number of alleles at a locus is the total number of individuals x 2
– The total number of dominant alleles at a locus is 2 alleles for each homozygous dominant individual plus 1 allele for each heterozygous individual; the same logic applies for recessive alleles |
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Term
| if there are 2 alleles at a locus, what are used to represent their frequencies? |
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Definition
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Term
| What does the Hardy-Weinberg principle describe? |
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Definition
| A population that is not evolving. |
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Term
| What states that frequencies of alleles and genotypes in a population remain constant from generation to generation? |
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Definition
| The Hardy-Weinberg principle |
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Term
| What three major factors alter allele frequencies and bring about most evolutionary change? |
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Definition
– Natural selection
– Genetic drift
– Gene flow |
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Term
| What results in certain alleles being passed to the next generation in greater proportions? |
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Definition
| Differential success in reproduction |
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Term
This describes how allele frequencies
fluctuate unpredictably from one generation to the next. |
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Definition
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Term
| This occurs when a few individuals become isolated from a larger population. |
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Definition
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Term
| What is it called when there is a sudden reduction in population size due to a change in the environment? |
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Definition
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Term
| What are 4 major effects of genetic drift? |
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Definition
1. Genetic drift is significant in small populations.
2. Genetic drift causes allele frequencies to change at random.
3. Genetic drift can lead to a loss of genetic variation within populations
4. Genetic drift can cause harmful alleles to become fixed. |
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Term
| What is described as the movement among alleles among populations? |
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Definition
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Term
| How can alleles be transferred? |
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Definition
| through the movement of fertile individuals or gametes (for example, pollen) |
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Term
| What does gene flow tend to do over time? |
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Definition
| Reduce the differences between populations. |
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Term
| What does gene flow do in terms of the fitness of a population? |
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Definition
| It can either increase or decrease the fitness of a population. |
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Term
| What is the contribution an individual makes to the gene pool of the next generation, relative to the contributions of other individuals? |
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Definition
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Term
| Why are The phrases “struggle for existence” and “survival of the fittest” misleading? |
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Definition
| they imply direct competition among individuals. |
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Term
| How does natural selection bring about adaptive evolution? |
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Definition
| By acting on an organisms phenotype. |
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Term
| What are the three models of selection? |
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Definition
1.Directional selection
2.Disruptive selection
3.stabilizing selection |
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Term
| This mode of selection favors individuals at one end of the phenotypic range. |
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Definition
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Term
This mode of selection favors
individuals at both extremes of the phenotypic range. |
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Definition
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Term
| This mode of selection n favors intermediate variants and acts against extreme phenotypes. |
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Definition
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Term
| What is the key role of natural selection? |
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Definition
It increases the frequencies of
alleles that enhance survival and reproduction. |
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Term
| This is natural selection for mating success. |
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Definition
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Term
| What can result from sexual selection? |
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Definition
| It can result in sexual dimorphism, marked differences between the sexes in secondary sexual characteristics. |
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Term
| This is competition among individuals of one sex (often males) for mates of the opposite sex. |
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Definition
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Term
| When does intrasexual selection occur? |
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Definition
When individuals of one sex (usually females) are choosy in selecting their
mates. |
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Term
| How do female preferences evolve? |
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Definition
| The good genes hypothesis suggests that if a trait is related to male health, both the male trait and female preference for that trait should be selected for. |
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Term
| How does diploidy maintain genetic variation? |
|
Definition
| In the form of hidden recessive genes. |
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|
Term
This occurs occurs when natural
selection maintains stable frequencies of two or more phenotypic forms in a population. |
|
Definition
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Term
| When does the heterozygote advantage occur? |
|
Definition
| when heterozygotes have a higher fitness than do both homozygotes. |
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Term
| The fitness of a phenotype declines if it becomes too common in the population. This is known as what? |
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Definition
| frequency-dependent selection |
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Term
What is genetic variation that
appears to confer no selective advantage or disadvantage? |
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Definition
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Term
| Why can't natural selection fashion perfect organisms? |
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Definition
1. Selection can act only on existing variations
2. Evolution is limited by historical constraints
3. Adaptations are often compromises
4. Chance, natural selection, and the
environment interact |
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Term
| Explain why natural selection is the only mechanism that consistently produces adaptive change. |
|
Definition
Natural selection brings about adaptive
evolution by acting on an organism’s
phenotype. |
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Term
| What is a point mutation? |
|
Definition
| A change in one base in a gene. |
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Term
| How can the effects of point mutations vary? |
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Definition
– Mutations in noncoding regions of DNA are often harmless.
– Mutations in a gene might not affect protein
production because of redundancy in the
genetic code.
– Mutations that result in a change in protein production are often harmful
– Mutations that result in a change in protein production can sometimes increase the fit between organism and environment. |
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Term
| What types of chromosomal mutations are typically harmful? |
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Definition
| Chromosomal mutations that delete, disrupt, or rearrange many loci are typically harmful. |
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Term
| What is the mutation rate like in plants and animals? |
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Definition
| very low. The average is about one mutation in every 100,000 genes per generation. |
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Term
In organisms that reproduce sexually,
what is more important than
mutation in producing the genetic differences that make adaptation possible? |
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Definition
|
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Term
| What does duplication usually do? |
|
Definition
• Duplication of large chromosome segments is usually harmful.
• Duplication of small pieces of DNA is
sometimes less harmful and increases the genome size.
• Duplicated genes can take on new functions by further mutation. |
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