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Unit 7

7.15 MC Answers and Review

6 min read•december 11, 2021

AP Biology 🧬

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Answers and Review for Multiple Choice Practice on Natural Selection

⛔STOP ⛔ Before you look at the answers, make sure you gave this practice quiz a try so you can assess your understanding of the concepts covered in Unit 7. Click here for the practice questions: AP Bio Unit 7 Multiple Choice Questions.

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Facts about the test: The AP Biology exam has 60 multiple choice questions and you will be given 1 hour 30 minutes to complete the section. That means it should take you around 15 minutes to complete 10 questions. The following questions were not written by College Board and although they cover information outlined in the AP Biology Course and Exam Description the formatting on the exam may be different.

1. For natural selection to occur, a population must have:

A. genetic variation

B. struggle to survive/competition

C. differential reproductive success

D. all of these

Answer: Natural selection, a mechanism of evolution, will occur if a population has genetic variation, some sort of struggle to survive (whether that be competition for food, mates, etc), and varying levels of reproduction. Those that are best "fit" for their particular environmental pressures will have increased survival and reproduction

📄 Study AP Biology, Unit 7.1: Introduction to Natural Selection

2. What does it mean if an organism is more "fit?"

A. stronger and faster

B. Higher reproductive success

C. older and wiser

D. beneficial mutations

Answer: Although a mutation may prove to be beneficial, mutations do not always results in improved fitness. Fitness describes how well the organism of a population survives and reproduces in its environment.

📄 Study AP Biology, Unit 7.1: Introduction to Natural Selection

3. The environmental pressure acts on the:

A. most fit individual

B. genotype

C. phenotype

D. hardy-Weinberg

Answer: The environment does not know which genotype produces the favorable trait. It is the PHENOTYPE (the physical trait) that the environment puts pressure on. Remember, more than one genotype can result in the same phenotype.

📄 Study AP Biology, Unit 7.4: Population Genetics

4. Antibiotic resistance caused by humans misusing antibiotics is an example of:

A. artificial selection

B. natural selection

C. convergent evolution

D. divergent evolution

Answer: For natural selection to be true, NATURE would be putting the pressure on bacteria. The overuse of antibiotics by humans is indeed an artificial way of putting selective pressure on a particular population of organisms.

📄 Study AP Biology, Unit 7.3: Artificial Selection

5. Choose the best example of convergent evolution:

A. Dolphins and sharks, although unrelated, share a similar adaptation: fins

B. Adaptive radiation of Galapagos finches

C. A population of beetles experience a change in allele frequency due to increased predation

D. Two populations of zebras become separated by a barrier and overtime become different species

Answer: To converge is to meet at a point. With respect to evolution it occurs when two independent populations possess similar traits due to similar environmental pressures. This does not indicate common ancestry.

📄 Study AP Biology, Unit 7.3: Artificial Selection

6. Two closely related organisms:

A. must have similar habitats

B. have the most genetic divergence

C. share a similar common ancestor

D. show fewer DNA similarities

Answer: Closely related organisms will have more genetic similarities and share a common ancestor. This means they have diverged from a recent similar organism.

📄 Study AP Biology, Unit 7.7: Common Ancestry

7. Similar structures due to common descent:

A. vestigial structures

B. analogous structures

C. homologous structure

D. none of these

Answer: While easily confused, analogous structures do not have similar structures, they may illustrate similar functions NOT due to common descent. Homologous structures may not have a similar function, but the similar structure provides evidence for common descent (common ancestor)

📄 Study AP Biology, Unit 7.6: Evidence of Evolution

8. The age of fossils can be found by:

A. rate of decay of isotopes

B. age of nearby rocks

C. geographical data

D. all of these

Answer: The question does not ask about "absolute" or "relative" age. The general task of determining age of a fossil found in the earth can be done in a variety of ways. Using rate of decay of isotopes gives scientists a more precise absolute age, while relative ages can be found by comparing rocks and other geographical data.

📄 Study AP Biology, Unit 7.6: Evidence of Evolution

9. The same allele advantageous in one environment proves to be disadvantageous in another environment. Why?

A. the advantageous allele mutates to a disadvantageous one

B. different environment, different selective pressure

C. different environments produce the same selective pressure

D. the environment changes depending on the allele

Answer: Natural selection relies on the environment for the selective pressure which ultimately causes the change in populations. If the same allele is present in a unique (different) environment, it will have a unique selective pressure as well. Look up the rock-pocket mice for a real life example of this!

📄 Study AP Biology, Unit 7.3: Artificial Selection

10. Phylogenetic trees show:

A. evolutionary relationships between organisms

B. similarities of embryonic development

C. similarities in morphology

D. quantifiable nucleotide differences

Answer: While nucleotide sequences and similarities in morphology/embryology can be used to BUILD a phylogenetic tree, trees illustrate the evolutionary relationships between organisms. Organisms most closely related will be found closer together on the tree.

📄 Study AP Biology, Unit 7.9: Phylogeny

11. Typically the BEST evidence when building phylogenetic trees:

A. comparisons of morphology

B. amino acid sequences

C. nucleotide sequences

D. derived characteristics

Answer: DNA is the end all be all! If there's a difference at the DNA level, it may not be noticeable at the amino acid level because of the redundant nature of codons (more than 1 codon can code for the same amino acid

📄 Study AP Biology, Unit 7.9: Phylogeny

12. How do you determine which organism is the outgroup when building a phylogenetic tree?

A. the organism with the least differences

B. the organism with the most differences

C. the organism with the most similarities

D. the organism who looks different from the rest

Answer: The outgroup is most different from the rest of the group. When building a tree it helps to determine which organism is the outgroup and place it furthest away from the others. This group is usually represented by the least number of shared characteristics or the most differences in nucleotide and amino acid sequences.

📄 Study AP Biology, Unit 7.9: Phylogeny

13. In the Hardy-Weinberg equation what does p2 represent?

A. the homozygous dominant phenotype

B. heterozygous genotype

C. homozygous recessive genotype

D. homozygous dominant genotype

Answer: p represents the dominant allele, so if we have pxp this represents two dominant alleles, which represents our homozygous dominant genotype.

📄 Study AP Biology, Unit 7.5: Hardy-Weinberg Equilibrium

14. A H-W problem gives you the frequency of the dominant trait. You begin solving by:

A. Setting that frequency to p2

B. Setting that frequency to q2

C. Use that frequency to find the frequency of the dominant allele

D. Use that frequency to find frequency of the recessive phenotype

Answer: This is a HUGE misconception from a lot of students. If given the dominant trait (phenotype) we do not know what percentage of that is the homozygous dominant genotype of heterozygous genotype. Starting with this number will not work. If given the frequency of the dominant TRAIT, you must first use it to find the recessive genotype. For example if 70% of the population displays the dominant phenotype, you can calculate that 30% will have the recessive trait. Now you know your q2.

📄 Study AP Biology, Unit 7.5: Hardy-Weinberg Equilibrium

15. Why can an extinction event create new opportunity for adaptive radiation?

A. New niches become available allowing different species to take advantage of resources

B. Extinction events occur during periods of environmental stress

C. extinction events have occurred throughout earth's history

D. Humans can cause extinction events

Answer: Although several options here are correct about extinctions in general, only one answers the specific question about WHY extinction can create opportunities for adaptive radiation to occur in a new environment.

📄 Study AP Biology, Unit 7.11: Extinction

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