Practice Guidance for BIOL 102 Exam 2 – Evolution, Population Genetics, and Speciation

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Q1. Which of the following best defines a species according to the biological species concept?

Background

Topic: Species Concepts

This question tests your understanding of how biologists define a species, specifically using the biological species concept.

Key Terms:

Species: A group of organisms that can interbreed and produce fertile offspring.
Biological Species Concept: Defines species based on the ability to interbreed and produce viable, fertile offspring.

Step-by-Step Guidance

Read each answer choice and identify which one focuses on reproductive compatibility rather than appearance or habitat.
Recall that the biological species concept emphasizes the ability to produce viable, fertile offspring.
Eliminate choices that focus only on physical similarity, habitat, or chromosome number.

Try solving on your own before revealing the answer!

Q2. Two nearly identical bird species live in the same forest but breed in different seasons. What type of reproductive isolation is this?

Background

Topic: Reproductive Isolation

This question tests your knowledge of the different types of reproductive barriers that prevent species from interbreeding.

Key Terms:

Reproductive Isolation: Mechanisms that prevent different species from interbreeding.
Temporal Isolation: When species breed at different times.
Behavioral Isolation: When species have different mating behaviors.

Step-by-Step Guidance

Identify the key detail: the species breed in different seasons.
Recall the definitions of each type of isolation listed in the answer choices.
Match the scenario to the correct type of isolation based on timing, behavior, or other mechanisms.

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Q3. Which of the following statements about artificial selection is true?

Background

Topic: Artificial Selection

This question tests your understanding of how artificial selection differs from natural selection and its effects on populations.

Key Terms:

Artificial Selection: The process by which humans select for desirable traits in organisms.
Natural Selection: Selection driven by environmental pressures, not human intervention.

Step-by-Step Guidance

Review each statement and determine if it describes artificial selection or natural selection.
Recall examples of artificial selection, such as dog breeding or crop improvement.
Identify which statement accurately reflects the outcomes or mechanisms of artificial selection.

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Q4. Scenario: A population of insects is sprayed with a pesticide. Most die, but a few survive due to a genetic trait that makes them resistant. Over time, the population consists mostly of resistant insects. This is an example of:

Background

Topic: Mechanisms of Evolution

This question tests your ability to identify evolutionary mechanisms such as natural selection, genetic drift, and bottleneck effect.

Key Terms:

Natural Selection: Differential survival and reproduction due to genetic traits.
Genetic Drift: Random changes in allele frequencies, especially in small populations.
Bottleneck Effect: A sharp reduction in population size leading to reduced genetic diversity.

Step-by-Step Guidance

Identify the selective pressure in the scenario (pesticide application).
Determine whether survival is due to chance or a specific genetic trait.
Match the scenario to the correct evolutionary mechanism based on the role of selection or chance.

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Q5. Which of the following is NOT an assumption of Hardy-Weinberg equilibrium?

Background

Topic: Population Genetics

This question tests your knowledge of the conditions required for a population to remain in Hardy-Weinberg equilibrium.

Key Terms:

Hardy-Weinberg Equilibrium: A model describing a non-evolving population.
Assumptions: No mutation, random mating, no gene flow, infinite population size, and no selection.

Step-by-Step Guidance

Recall the five main assumptions of Hardy-Weinberg equilibrium.
Compare each answer choice to the list of assumptions.
Identify which choice does not fit with the Hardy-Weinberg model.

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Q6. What is the difference between microevolution and macroevolution?

Background

Topic: Evolutionary Processes

This question tests your understanding of the scale and outcomes of evolutionary change.

Key Terms:

Microevolution: Changes in allele frequencies within a population over time.
Macroevolution: Evolutionary changes that result in the formation of new species or higher taxonomic groups.

Step-by-Step Guidance

Review the definitions of microevolution and macroevolution.
Identify which answer choices correctly distinguish between changes within populations and the formation of new species.
Eliminate choices that confuse the scale or mechanisms of these processes.

Try solving on your own before revealing the answer!

Q7. Which of the following is an example of convergent evolution?

Background

Topic: Patterns of Evolution

This question tests your ability to recognize convergent evolution, where unrelated species evolve similar traits.

Key Terms:

Convergent Evolution: Independent evolution of similar features in species of different lineages.
Homology vs. Analogy: Homologous traits are inherited from a common ancestor; analogous traits arise independently.

Step-by-Step Guidance

Identify which examples involve similar traits in unrelated groups.
Recall that convergent evolution produces analogous structures, not homologous ones.
Eliminate choices that involve shared ancestry or adaptation to different environments within a lineage.

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Q8. Scenario: A flood drastically reduces the size of a population of rabbits. The remaining population has much lower genetic diversity than before. This is an example of:

Background

Topic: Genetic Drift and Population Bottlenecks

This question tests your understanding of how population size reductions affect genetic diversity.

Key Terms:

Bottleneck Effect: A sharp reduction in population size due to a random event, leading to loss of genetic variation.
Founder Effect: When a new population is established by a small number of individuals.

Step-by-Step Guidance

Identify the cause of population reduction (flood) and its effect on genetic diversity.
Recall the definitions of bottleneck and founder effects.
Determine which term best describes a reduction in genetic diversity due to a drastic decrease in population size.

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Q9. The allele for polydactyly (extra fingers or toes) is dominant, yet it is not the most common trait in human populations. This is because:

Background

Topic: Dominance and Allele Frequency

This question tests your understanding of the relationship between dominance and allele frequency in populations.

Key Terms:

Dominant Allele: An allele that is expressed in the phenotype even if only one copy is present.
Allele Frequency: The proportion of a specific allele among all alleles in a population.

Step-by-Step Guidance

Recall that dominance does not determine how common an allele is in a population.
Review the definitions of dominant and recessive alleles.
Identify which answer choice correctly explains why a dominant trait can be rare.

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Q10. A hybrid zone can have three possible outcomes over time. Which of the following is NOT one of these outcomes?

Background

Topic: Speciation and Hybrid Zones

This question tests your knowledge of the possible outcomes when two species interbreed in a hybrid zone.

Key Terms:

Hybrid Zone: A region where members of different species meet and mate.
Reinforcement, Fusion, Stability: The three main outcomes for hybrid zones.

Step-by-Step Guidance

Recall the three possible outcomes for hybrid zones: reinforcement, fusion, and stability.
Review each answer choice and determine if it matches one of these outcomes.
Identify the choice that does not fit with the established outcomes of hybrid zones.

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Q11. If a certain allele occurs with a frequency of 0.3 in a population, what is the frequency of the other allele, assuming only two alleles exist?

Background

Topic: Hardy-Weinberg Equilibrium and Allele Frequencies

This question tests your ability to calculate allele frequencies when only two alleles are present in a population.

Key Formula:

Where and are the frequencies of the two alleles.

Step-by-Step Guidance

Let be the frequency of one allele (given as 0.3).
Recall that the sum of the frequencies of both alleles must equal 1.
Set up the equation and solve for .

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Q12. Which of the following describes how genetic drift differs from natural selection?

Background

Topic: Mechanisms of Evolution

This question tests your understanding of the differences between genetic drift and natural selection.

Key Terms:

Genetic Drift: Random changes in allele frequencies, especially in small populations.
Natural Selection: Non-random process where traits that confer a fitness advantage become more common.

Step-by-Step Guidance

Review the definitions of genetic drift and natural selection.
Identify which answer choice correctly contrasts the role of chance versus fitness advantage.
Eliminate choices that incorrectly describe the effects or requirements of each process.

Try solving on your own before revealing the answer!

Q13. What does the principle of parsimony suggest when constructing phylogenetic trees?

Background

Topic: Phylogenetics

This question tests your understanding of how scientists infer evolutionary relationships using the principle of parsimony.

Key Terms:

Parsimony: The simplest explanation, requiring the fewest evolutionary changes, is preferred.
Phylogenetic Tree: A diagram showing evolutionary relationships among species.

Step-by-Step Guidance

Recall the definition of parsimony in the context of evolutionary biology.
Review each answer choice and determine which one aligns with the principle of minimizing evolutionary changes.
Eliminate choices that focus on data type or superficial similarity.

Try solving on your own before revealing the answer!

Q14. Why are molecular homologies often considered more reliable than anatomical homologies in constructing phylogenies?

Background

Topic: Phylogenetics and Homology

This question tests your understanding of the advantages of using molecular data in evolutionary studies.

Key Terms:

Molecular Homology: Similarities in DNA or protein sequences due to shared ancestry.
Anatomical Homology: Similarities in structure due to shared ancestry.

Step-by-Step Guidance

Recall why molecular data can provide more detailed or objective information than anatomical traits.
Review each answer choice and identify which one best explains the reliability of molecular homologies.
Eliminate choices that overstate or misrepresent the role of molecular or anatomical data.

Try solving on your own before revealing the answer!

Q15. Which of the following is an example of allopatric speciation?

Background

Topic: Speciation

This question tests your ability to recognize allopatric speciation, which occurs when populations are geographically separated.

Key Terms:

Allopatric Speciation: Speciation that occurs when populations are separated by a physical barrier.
Sympatric Speciation: Speciation without geographic separation.

Step-by-Step Guidance

Identify which scenarios involve geographic isolation of populations.
Recall that allopatric speciation requires a physical barrier to gene flow.
Eliminate choices that describe speciation within the same geographic area.

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Q16. What is the role of hybrid zones in speciation?

Background

Topic: Hybrid Zones and Speciation

This question tests your understanding of how hybrid zones can influence the process of speciation.

Key Terms:

Hybrid Zone: A region where two species meet and interbreed.
Gene Flow: The transfer of alleles between populations.

Step-by-Step Guidance

Recall the possible outcomes of hybrid zones: reinforcement, fusion, and stability.
Review each answer choice and determine which one accurately describes the role of hybrid zones.
Eliminate choices that overgeneralize or misrepresent the outcomes of hybrid zones.

Try solving on your own before revealing the answer!

Q17. Which of the following correctly defines "descent with modification"?

Background

Topic: Evolutionary Theory

This question tests your understanding of Darwin's concept of evolution by descent with modification.

Key Terms:

Descent with Modification: The process by which species change over time, giving rise to new species.
Inheritance: Passing of genetic traits from parents to offspring.

Step-by-Step Guidance

Recall that descent with modification involves both inheritance and change over generations.
Review each answer choice and identify which one best captures the idea of evolutionary change over time.
Eliminate choices that confuse individual adaptation with population-level change.

Try solving on your own before revealing the answer!

Q18. In a phylogenetic tree, what does a branch point represent?

Background

Topic: Phylogenetics

This question tests your understanding of how to interpret phylogenetic trees and the meaning of branch points (nodes).

Key Terms:

Branch Point (Node): Represents the most recent common ancestor of the descendant lineages.
Phylogenetic Tree: Diagram showing evolutionary relationships.

Step-by-Step Guidance

Recall what a branch point (node) indicates in a phylogenetic tree.
Review each answer choice and determine which one matches the definition of a branch point.
Eliminate choices that describe extinction, mutations, or geographic barriers.

Try solving on your own before revealing the answer!

Q19. Which of the following is NOT a requirement for Hardy-Weinberg equilibrium?

Background

Topic: Population Genetics

This question tests your knowledge of the conditions necessary for a population to remain in Hardy-Weinberg equilibrium.

Key Terms:

Hardy-Weinberg Equilibrium: Describes a non-evolving population under specific conditions.
Assumptions: No mutation, random mating, no gene flow, large population size, and no selection.

Step-by-Step Guidance

Recall the five main requirements for Hardy-Weinberg equilibrium.
Compare each answer choice to the list of requirements.
Identify which choice is NOT a requirement for Hardy-Weinberg equilibrium.

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Q20. You have sampled a population in which you know that the percentage of the homozygous recessive genotype (aa) is 36%. Using that 36%, calculate the following:

Background

Topic: Hardy-Weinberg Equilibrium Calculations

This question tests your ability to use Hardy-Weinberg equations to calculate genotype and allele frequencies.

Key Formulas:

Where = frequency of dominant allele, = frequency of recessive allele, = frequency of homozygous dominant, = frequency of heterozygotes, = frequency of homozygous recessive.

Step-by-Step Guidance

Recognize that (frequency of aa) is given as 0.36.
Take the square root of to find (frequency of the a allele): .
Calculate using .
Calculate (frequency of AA) and (frequency of Aa) using the Hardy-Weinberg equation.
Determine the frequencies of the two phenotypes, remembering that "A" is completely dominant over "a" (so AA and Aa have the dominant phenotype, aa is recessive).

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Q21. If 98 out of 200 individuals in a population express the recessive phenotype, what percent of the population would you predict would be heterozygotes?

Background

Topic: Hardy-Weinberg Equilibrium and Genotype Frequencies

This question tests your ability to use observed phenotype frequencies to calculate genotype frequencies using Hardy-Weinberg equations.

Key Formulas:

Step-by-Step Guidance

Calculate the frequency of the recessive phenotype: .
Take the square root of to find .
Calculate using .
Use to find the frequency of heterozygotes in the population.
To check your work, add the frequencies of all three genotypes (, , ) and confirm they sum to 1 (or 100%).