Ap Bio Unit 7 Practice Questions

Conquer AP Biology Unit 7: A Deep Dive into Practice Questions

AP Biology Unit 7, focusing on natural selection, is a crucial stepping stone towards understanding the intricate dance of life on Earth. Mastering this unit is not just about memorizing definitions, but about grasping the underlying principles that drive evolution and adaptation. To truly cement your understanding, practicing with targeted questions is essential. This article will explore a variety of practice questions covering the core concepts of Unit 7, providing detailed explanations and strategies to help you ace your AP Biology exam.

Why Practice Questions are Key to AP Biology Success

Simply reading textbooks and attending lectures isn't enough to guarantee success in AP Biology. Practice questions offer several key benefits:

• Reinforce Learning: Applying concepts through problem-solving strengthens your understanding and helps you retain information better.
• Identify Weaknesses: Practice questions expose areas where you need more focused study. Recognizing these gaps allows you to prioritize your learning.
• Improve Time Management: The AP Biology exam is timed, so practicing under simulated test conditions helps you develop efficient time management skills.
• Develop Critical Thinking: Many AP Biology questions require critical thinking and analytical skills. Regular practice hones these abilities.
• Familiarize Yourself with the Exam Format: Practice questions expose you to the style and format of questions you'll encounter on the actual AP exam.

Key Concepts in AP Biology Unit 7

Before diving into practice questions, let's briefly review the core concepts covered in Unit 7:

• Natural Selection: The driving force behind evolution, where organisms with advantageous traits are more likely to survive and reproduce.
• Variation: The raw material for natural selection, stemming from mutations, sexual reproduction, and other genetic mechanisms.
• Adaptation: Heritable traits that enhance an organism's survival and reproductive success in a specific environment.
• Evidence of Evolution: Fossils, anatomical similarities, embryological development, biogeography, and molecular data all provide compelling evidence for evolution.
• Hardy-Weinberg Equilibrium: A null hypothesis that describes the conditions under which allele and genotype frequencies in a population remain constant from generation to generation.
• Mechanisms of Evolution: Natural selection, genetic drift (founder effect and bottleneck effect), gene flow, and mutation.
• Speciation: The process by which new species arise, often driven by reproductive isolation.
• Phylogeny: The evolutionary history and relationships of organisms, often represented in phylogenetic trees.

Practice Questions with Detailed Explanations

Now, let's tackle some practice questions that cover these key concepts. Each question is followed by a detailed explanation to help you understand the underlying principles.

Question 1:

A population of butterflies exhibits variation in wing color, ranging from light brown to dark brown. Birds prey on these butterflies, and the light brown butterflies are more visible against the dark tree bark in their habitat. Over time, what is the most likely outcome for this butterfly population?

(A) The frequency of the light brown allele will increase. (B) The frequency of the dark brown allele will increase. (C) The population will become entirely light brown. (D) The population will become entirely dark brown.

Explanation:

The correct answer is (B) The frequency of the dark brown allele will increase. This scenario describes natural selection. The dark brown butterflies have a survival advantage because they are better camouflaged against the tree bark, making them less likely to be preyed upon by birds. This means they are more likely to survive, reproduce, and pass on their dark brown alleles to the next generation. Over time, this will lead to an increase in the frequency of the dark brown allele within the population.

Question 2:

Which of the following is NOT a condition that must be met for a population to be in Hardy-Weinberg equilibrium?

(A) No mutation (B) Random mating (C) Small population size (D) No gene flow

Explanation:

The correct answer is (C) Small population size. The five conditions for Hardy-Weinberg equilibrium are:

1. No mutation: The rate of new mutations must be negligible.
2. Random mating: Individuals must mate randomly, without preference for certain genotypes.
3. No natural selection: All genotypes must have equal survival and reproductive rates.
4. Extremely large population size: The population must be large enough to avoid random fluctuations in allele frequencies due to chance (genetic drift).
5. No gene flow: There must be no migration of individuals (and their alleles) into or out of the population.

A small population size increases the likelihood of genetic drift, which can significantly alter allele frequencies and disrupt Hardy-Weinberg equilibrium.

Question 3:

The Mycoplasma genitalium genome consists of only 525 genes. Scientists hypothesize that this bacterium represents the minimal gene set necessary for life. Which of the following experimental approaches would BEST test this hypothesis?

(A) Introduce random mutations into Mycoplasma genitalium and observe which mutations are lethal. (B) Compare the Mycoplasma genitalium genome with the genomes of more complex bacteria. (C) Attempt to synthesize a functional Mycoplasma genitalium cell with only the 525 genes. (D) Introduce genes from more complex bacteria into Mycoplasma genitalium and observe the effects on its growth.

Explanation:

The correct answer is (C) Attempt to synthesize a functional Mycoplasma genitalium cell with only the 525 genes. This approach directly tests whether the 525 genes are sufficient for life. If scientists can synthesize a functional cell with these genes, it supports the hypothesis.

• Option (A) would identify essential genes, but it doesn't prove that only those 525 are necessary.
• Option (B) provides comparative data, but it doesn't experimentally test the hypothesis.
• Option (D) explores gene function but doesn't address the minimal gene set requirement.

Question 4:

Two populations of frogs are separated by a mountain range. Over time, genetic differences accumulate between the two populations due to genetic drift and natural selection. If the mountain range erodes, allowing the two populations to interbreed, which of the following outcomes is MOST likely?

(A) The two populations will immediately merge into a single, homogeneous population. (B) The two populations will continue to diverge, eventually forming two distinct species. (C) The two populations will interbreed, producing hybrid offspring with reduced fitness. (D) The two populations will interbreed, producing hybrid offspring with increased fitness.

Explanation:

The most likely answer is (C) The two populations will interbreed, producing hybrid offspring with reduced fitness. This scenario describes a situation where reproductive isolation has begun to develop. While the populations can still interbreed, the accumulated genetic differences may lead to hybrid offspring with lower survival or reproductive rates (reduced fitness). This is often due to incompatible gene combinations. Options A, B, and D are less likely in the immediate aftermath of the barrier removal. Complete merging (A) requires hybrids to be equally or more fit than parental populations. Continued divergence (B) requires continued reproductive isolation despite the physical barrier being gone. Increased fitness of hybrids (D) is possible but less common than reduced fitness after a period of separation.

Question 5:

Which of the following provides the strongest evidence for the common ancestry of all life on Earth?

(A) The presence of similar anatomical structures in different species. (B) The universality of the genetic code and the use of DNA as the primary genetic material. (C) The observation that all organisms require energy to survive. (D) The fact that all organisms reproduce.

Explanation:

The correct answer is (B) The universality of the genetic code and the use of DNA as the primary genetic material. While options A, C, and D are all characteristics of life, the universality of the genetic code (where the same codons specify the same amino acids in almost all organisms) and the use of DNA as the hereditary molecule are powerful indicators of a shared evolutionary origin. This suggests that all life evolved from a common ancestor that used DNA and this specific code. Anatomical similarities (A) could be due to convergent evolution, and energy requirements (C) and reproduction (D) are simply fundamental requirements for life.

Question 6:

A scientist is studying a population of fish in a lake. She observes that the average size of the fish has increased over the past 20 years. Which of the following is the LEAST likely explanation for this observation?

(A) Natural selection favoring larger fish due to increased competition for food. (B) Increased mutation rate leading to the production of larger offspring. (C) Changes in the lake environment, such as increased nutrient availability, allowing fish to grow larger. (D) Genetic drift causing a random increase in the frequency of alleles for larger size.

Explanation:

The correct answer is (B) Increased mutation rate leading to the production of larger offspring. While mutations are the source of variation, a significant and directional increase in size due solely to mutation is highly improbable. Mutation rates are generally low, and most mutations are either neutral or harmful. It's unlikely that a sudden increase in mutation rate would consistently produce beneficial mutations leading to larger size. The other options are more plausible explanations.

Question 7:

A population of lizards lives on a rocky island. Some lizards have long legs, allowing them to run quickly over the rocks, while others have short legs, providing better stability. A hurricane hits the island, washing away many of the smaller rocks and leaving behind larger, more uneven surfaces. What is the most likely outcome for the lizard population after the hurricane?

(A) The frequency of the long-legged allele will increase. (B) The frequency of the short-legged allele will increase. (C) The population will become entirely long-legged. (D) The population will remain unchanged.

Explanation:

The correct answer is (B) The frequency of the short-legged allele will increase. The hurricane has changed the environment, making the larger, uneven rocks more prevalent. Short legs now provide a survival advantage because they offer better stability on these surfaces. Lizards with short legs will be better able to navigate the environment, find food, and avoid predators, leading to an increase in the frequency of the short-legged allele in the population.

Question 8:

Which of the following is an example of allopatric speciation?

(A) A population of insects develops resistance to a pesticide. (B) A population of plants evolves different flowering times, preventing cross-pollination. (C) A population of squirrels is divided by a newly formed canyon, leading to the evolution of two distinct species. (D) A population of bacteria acquires a new gene through horizontal gene transfer.

Explanation:

The correct answer is (C) A population of squirrels is divided by a newly formed canyon, leading to the evolution of two distinct species. Allopatric speciation occurs when a population is divided by a geographic barrier, preventing gene flow between the two subpopulations. Over time, these subpopulations accumulate genetic differences due to natural selection and genetic drift, eventually leading to reproductive isolation and the formation of two distinct species.

• Option (A) describes adaptation within a population.
• Option (B) describes sympatric speciation (speciation without geographic isolation).
• Option (D) describes a mechanism of genetic variation but not speciation.

Question 9:

The graph shows the number of individuals with different beak depths in a population of finches. Before a drought, the beak depths were normally distributed. After the drought, the graph shows a shift towards larger beak depths. Which type of selection is most likely responsible for this change?

(A) Stabilizing selection (B) Directional selection (C) Disruptive selection (D) Sexual selection

Explanation:

The correct answer is (B) Directional selection. Directional selection occurs when natural selection favors individuals at one extreme of a phenotypic range. In this case, the drought favored finches with larger beak depths, causing a shift in the population's distribution towards that extreme.

• Stabilizing selection favors intermediate phenotypes.
• Disruptive selection favors both extremes of a phenotypic range.
• Sexual selection favors traits that increase mating success.

Question 10:

Scientists compare the DNA sequences of several different species. They find that Species A and Species B have very similar DNA sequences, while Species A and Species C have more divergent DNA sequences. Which of the following conclusions is most likely supported by this data?

(A) Species A and Species B are more closely related to each other than Species A and Species C. (B) Species A evolved from Species B. (C) Species C evolved from Species A. (D) Species A is the ancestor of all three species.

Explanation:

The correct answer is (A) Species A and Species B are more closely related to each other than Species A and Species C. DNA sequence similarity is a strong indicator of evolutionary relatedness. Species with more similar DNA sequences share a more recent common ancestor. The other options are too strong of claims based solely on DNA sequence data. While A and B are closely related, it doesn't necessarily mean one evolved directly from the other, or that A is the ancestor of all.

Tips for Answering AP Biology Questions

• Read the questions carefully: Pay attention to key words and phrases, such as "NOT," "EXCEPT," "MOST likely," and "LEAST likely."
• Understand the concepts: Don't just memorize facts. Focus on understanding the underlying principles.
• Eliminate incorrect answers: Use the process of elimination to narrow down your choices.
• Relate the questions to real-world examples: This can help you visualize the concepts and make connections.
• Practice, practice, practice: The more you practice, the more comfortable you'll become with the exam format and the types of questions asked.
• Review your mistakes: Analyze why you got a question wrong and learn from your errors.

Additional Resources for AP Biology Unit 7

• AP Biology Textbooks: Consult your textbook for detailed explanations of the concepts.
• Online Resources: Khan Academy, Bozeman Science, and other websites offer excellent AP Biology resources.
• AP Biology Review Books: These books provide comprehensive reviews of the material and practice questions.
• College Board Website: The College Board website provides information about the AP Biology exam, including sample questions and scoring guidelines.

Conclusion

Mastering AP Biology Unit 7 requires a deep understanding of the principles of natural selection and evolution. By working through practice questions and carefully reviewing the explanations, you can strengthen your knowledge, identify areas for improvement, and develop the critical thinking skills necessary to succeed on the AP exam. Remember to focus on understanding the concepts, applying them to different scenarios, and practicing consistently. Good luck!