AP Biology : Theorists and Evidence

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #21 : Evolution And Genetics

Gregor Mendel, an Augustinian friar, studied genetics through what types of experiments?

Possible Answers:

Calculated economic impact of population growth 

Studying museum specimens

Crossbreeding pea plants

Studying finches

Correct answer:

Crossbreeding pea plants

Explanation:

Gregor Mendel studied genetics through the crossbreeding of pea plants. Through his studies, he proposed laws of heredity (the law of segregation, the law of independent assortment, and the law of dominance), that are now called the laws of Mendelian inheritance. Darwin famously studied finches on the Galapagos Islands.

Example Question #21 : Theorists And Evidence

If two heterozygous yellow plants are mated with one another, what percent of the offspring will be yellow? Assume complete dominance.

Possible Answers:

Correct answer:

Explanation:

Heterozygous organisms carry one dominant allele and one recessive allele. The dominant allele is expressed over the recessive allele, giving the organism the dominant phenotype. If the heterozygous plants in the question are yellow, then we can conclude that yellow is dominant to some other phenotype (not given).

The cross for these two plants would be:

Parents: Yy (yellow) x Yy (yellow)

Offspring: YY (yellow), Yy (yellow), Yy (yellow), yy (other/unknown)

Three of the four possible offspring will show the dominant yellow phenotype, leading to the answer: 75%.

Example Question #23 : Evolution And Genetics

Which of the following concepts was not discovered by the scientist Gregor Mendel?

Possible Answers:

Organisms have two alleles for each trait, one allele from each parent.

The likelihood of alleles for different traits being inherited together is based on how close together those alleles are on the chromosome.

The traits of organisms are determined by factors inherited from their parents.

Alleles for different traits are passed down from parents to offspring independently from each other.

The effects of recessive alleles are masked by the presence of dominant alleles.

Correct answer:

The likelihood of alleles for different traits being inherited together is based on how close together those alleles are on the chromosome.

Explanation:

The overall idea that Mendel was studying was that organisms have two alleles per trait, and that each parent passes down one allele. The other answers refer to Mendel’s laws: the Law of Segregation, the Law of Independent Assortment, and the Law of Dominance. Mendel was unaware of genetic linkage, which is an exception to the Law of Independent Assortment. We know this to be true because chromosomes and DNA had not yet been discovered in his time.

Example Question #24 : Evolution And Genetics

Gregor Mendel’s major contribution to the study of inheritance was to show that __________.

Possible Answers:

DNA exists

individual particles in various combinations can produce traits

dominant alleles appear more in male pea plants than in female pea plants

a dominant allele is stronger than a recessive allele

Correct answer:

individual particles in various combinations can produce traits

Explanation:

Gregor Mendel's famous work on pea plants built our first understandings of inheritance. He identified that "discrete particles", which we now call genes and alleles, are passed to offspring in numerous of combinations. These different combinations create variation in a population.

Example Question #25 : Evolution And Genetics

The sum of all genetic alleles in a population is the __________.

Possible Answers:

gene frequency

gene stock

gene resources

gene pool

gene supply

Correct answer:

gene pool

Explanation:

A population is composed of numerous individuals, each carrying a common set of genes with a unique combination of genetic alleles. The gene pool is the sum of all of these alleles.

Example Question #26 : Evolution And Genetics

Which term refers to the relative proportions of a specific allele in relation to all alleles for the given gene in a population?

Possible Answers:

Allele coefficient

Allele amount

Allele population

Allele concentration

Allele frequency

Correct answer:

Allele frequency

Explanation:

The allele frequency for any given gene is the relative proportion of each allele of that gene in a population. This value can be found by dividing the number of a specific allele by the total number of alleles in a population.

Example Question #27 : Evolution And Genetics

Mutation, gene flow, nonrandom mating, and natural selection combine to cause which of the following?

Possible Answers:

Reproduction

Evolution

Genetic drift

Mutations

Segregation

Correct answer:

Evolution

Explanation:

Evolution is any change in the proportions of different genotypes in a population from one generation to the next. Mutation, geneflow, nonrandom mating, and natural selection all contribute toward favoring certain alleles over others within a population. This leads to changes in allele frequency, and subsequent evolution.

Example Question #28 : Evolution And Genetics

The requirements for Hardy-Weinberg equilibrium are designed to create which scenario for the given population?

Possible Answers:

Evolution will not occur

Nonrandom mating will flourish

Extinction is eminent

Divergency will occur

Mutations will be common

Correct answer:

Evolution will not occur

Explanation:

The Hardy-Weinberg principle is a mathematical model that states that, under certain conditions, the allele frequencies and genotype frequencies in a sexually reproducing population will remain constant over generations. This consistency means that evolution is not occurring, as evolution (by definition) requires a change in allele frequency.

Requirements for Hardy-Weinberg equilibrium include: large population size, no mutation, no migration, random mating, and no natural selection.

Example Question #29 : Evolution And Genetics

A process in which chance events are likely to change allele frequencies in a small population is known as __________.

Possible Answers:

bottleneck effect

genetic drift

allele fluctuation

evolution

natural selection

Correct answer:

genetic drift

Explanation:

Genetic drift is a change in the allele frequencies of a small population purely by chance.

The bottleneck effect occurs when allele frequencies are affected by a cataclysmic event. Evolution refers to a change in allele frequency, but is not limited to small populations or random chance. Natural selection refers to changes in allele frequency due to specific conditions, as opposed to random chance.

Example Question #30 : Evolution And Genetics

Which of the following are characteristics that help an individual survive and reproduce in an environment?

Possible Answers:

Habits

Traits

Adaptations

Mutations

Skills

Correct answer:

Adaptations

Explanation:

An adaptation is a characteristic of an organism that helps it survive and reproduce in a particular environment. Adaptations are the result of random mutations that have favorable outcomes. The favorability of these traits enables offspring that inherit them to thrive, thus increasing their prevalence in the population.

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