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 viable, fertile offspring.
Biological Species Concept: Focuses on reproductive isolation as the main criterion for defining species.

Step-by-Step Guidance

Read each answer choice and identify which one emphasizes the ability to interbreed and produce fertile offspring.
Recall that the biological species concept is based on reproductive isolation, not just physical similarity or habitat.
Eliminate choices that focus on appearance, habitat, or chromosome number rather than reproductive compatibility.

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 Mechanisms

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: Occurs when species breed at different times.
Behavioral Isolation: Involves differences in mating behaviors.

Step-by-Step Guidance

Identify the key detail: the species breed in different seasons (times).
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 versus behavior, mechanics, or gametes.

Try solving on your own before revealing the answer!

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 traits in populations.

Key Terms:

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

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.

Try solving on your own before revealing the answer!

Q4. 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 distinguish between different evolutionary processes, such as natural selection, genetic drift, and bottleneck effects.

Key Terms:

Natural Selection: Differential survival and reproduction due to inherited traits.
Genetic Drift: Random changes in allele frequencies, especially in small populations.
Bottleneck Effect: A sharp reduction in population size due to a random event.

Step-by-Step Guidance

Identify the cause of survival: Is it random or due to a specific trait?
Recall which evolutionary mechanism involves selection for advantageous traits.
Eliminate options that do not fit the scenario described (e.g., random chance vs. selection).

Try solving on your own before revealing the answer!

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

Background

Topic: Population Genetics – Hardy-Weinberg Principle

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

Key Terms and Formula:

Hardy-Weinberg Equilibrium: A model that describes allele and genotype frequencies in a non-evolving population.
Assumptions: No mutation, random mating, no gene flow, infinite population size, and no selection.

Step-by-Step Guidance

Review each answer choice and compare it to the five Hardy-Weinberg assumptions.
Identify which choice contradicts the requirements for equilibrium.
Eliminate choices that are actual assumptions of the model.

Try solving on your own before revealing the answer!

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

Recall the definitions of microevolution and macroevolution.
Compare the scale (within populations vs. above the species level) and outcomes (allele frequency change vs. speciation).
Eliminate choices that confuse the two or are factually incorrect.

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.
Homoplasy: Similar traits not due to common ancestry.

Step-by-Step Guidance

Identify which example involves unrelated species developing similar adaptations.
Recall that convergent evolution does not involve shared ancestry for the trait.
Eliminate examples that involve divergence from a common ancestor or adaptation to different environments.

Try solving on your own before revealing the answer!

Q8. 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 diversity.
Founder Effect: When a new population is started by a small number of individuals.

Step-by-Step Guidance

Identify the cause of population reduction (random event vs. selection).
Recall the definitions of bottleneck and founder effects.
Choose the answer that best matches a random reduction in population size and genetic diversity.

Try solving on your own before revealing the answer!

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 guarantee high frequency in a population.
Review each answer choice for misconceptions about dominance and allele prevalence.
Choose the statement that correctly explains why a dominant trait can be rare.

Try solving on your own before revealing the answer!

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, producing hybrids.
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.

Try solving on your own before revealing the answer!

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 Principle – Allele Frequencies

This question tests your ability to use the Hardy-Weinberg equation to calculate allele frequencies.

Key Formula:

= frequency of one allele
= frequency of the other allele

Step-by-Step Guidance

Identify the given allele frequency (e.g., ).
Recall that the sum of the frequencies of both alleles must equal 1.
Set up the equation and solve for the unknown allele frequency.

Try solving on your own before revealing the answer!

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 advantageous traits increase in frequency.

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 advantages.
Eliminate choices that incorrectly describe the effects or mechanisms of these processes.

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 choose between different possible evolutionary trees.

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 principle of parsimony in scientific reasoning.
Review each answer choice for references to simplicity or number of changes.
Choose the statement that best matches the principle of parsimony.

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: Molecular vs. Anatomical Evidence in Phylogenetics

This question tests your understanding of why DNA and protein comparisons are useful in evolutionary studies.

Key Terms:

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

Step-by-Step Guidance

Recall the advantages of molecular data (e.g., more data points, less subject to convergent evolution).
Review each answer choice for accuracy regarding molecular and anatomical evidence.
Choose the statement that best explains the reliability of molecular homologies.

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

Background

Topic: Speciation Mechanisms

This question tests your ability to recognize examples of speciation due to geographic isolation.

Key Terms:

Allopatric Speciation: Speciation that occurs when populations are geographically separated.
Sympatric Speciation: Speciation without geographic separation.

Step-by-Step Guidance

Identify which scenario involves a physical barrier separating populations.
Recall that allopatric speciation requires geographic isolation.
Eliminate choices that do not involve geographic separation.

Try solving on your own before revealing the answer!

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 influence the process of speciation.

Key Terms:

Hybrid Zone: Area where two species meet and interbreed, producing hybrids.
Reinforcement, Fusion, Stability: Possible outcomes of hybrid zones.

Step-by-Step Guidance

Recall the three possible outcomes for hybrid zones.
Review each answer choice for accuracy regarding gene flow and speciation outcomes.
Choose the statement that best summarizes the role 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 natural selection.

Key Terms:

Descent with Modification: The idea that species change over time, giving rise to new species, with all organisms sharing a common ancestor.

Step-by-Step Guidance

Recall the meaning of "descent with modification" in evolutionary biology.
Review each answer choice for accuracy regarding inheritance and change over generations.
Eliminate choices that suggest no change or individual evolution within a lifetime.

Try solving on your own before revealing the answer!

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

Background

Topic: Phylogenetic Trees

This question tests your understanding of how to interpret evolutionary relationships in a phylogenetic tree.

Key Terms:

Branch Point (Node): Represents the most recent common ancestor of the descendant lineages.

Step-by-Step Guidance

Recall what a node or branch point indicates in a phylogenetic tree.
Review each answer choice for references to ancestry, extinction, or mutations.
Choose the statement that correctly describes the meaning of a branch point.

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 – Hardy-Weinberg Principle

This question tests your knowledge of the five requirements for Hardy-Weinberg equilibrium.

Key Terms:

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

Step-by-Step Guidance

Review each answer choice and compare it to the five Hardy-Weinberg requirements.
Identify which choice is NOT a requirement for equilibrium.
Eliminate choices that are actual requirements of the model.

Try solving on your own before revealing the answer!

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 Calculations

This question tests your ability to use genotype frequencies to calculate allele and genotype frequencies in a population.

Key Formulas:

= frequency of homozygous recessive (aa)
= frequency of homozygous dominant (AA)
= frequency of heterozygotes (Aa)

Step-by-Step Guidance

Convert the percentage of homozygous recessive individuals to a decimal: .
Solve for by taking the square root of .
Calculate using .
Calculate (frequency of AA) and (frequency of Aa).
For phenotype frequencies, remember that if A is completely dominant, both AA and Aa show the dominant phenotype, while aa shows the recessive phenotype.

Try solving on your own before revealing the answer!

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 Calculations

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

Key Formulas:

= frequency of homozygous recessive individuals (recessive phenotype)
= frequency of heterozygotes
= frequency of homozygous dominant individuals

Step-by-Step Guidance

Calculate the frequency of the recessive phenotype: .
Solve for by taking the square root of .
Calculate using .
Calculate the frequency of heterozygotes using .
To check your work, add the frequencies of all three genotypes (, , ) and confirm they sum to 1 (or 100%).