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Unit 8

8.9 MC Answers and Review

7 min readdecember 11, 2021


AP Biology 🧬

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Answers and Review for Multiple Choice Practice on Ecology

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 8. Click here for the practice questions: AP Bio Unit 8 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. A group of behavioral ecologists seeks to find if there is a relationship between the number of ocelli (or eyespots) on a peacock's tail and female interest in the male (courtship behavior). Scientists quantified female interest by documenting number of visits an duration of the visit. Identify the independent variable.
A. Duration of visit
B. Hue of eye spot
C. Number of ocelli
D. Number of visits
Answer: The number of visits and duration of visits are the DEPENDENT variable because they are the "measured" variable. Scientists were wanting to discover the impact that the number of ocelli had on female interest. The independent variable must be the # of eyespots.
📄 Study AP Biology, Unit 8.1: Responses to the Environment

2. In the peacock behavior experiment, what could serve as the control group?
A. Peacock's with the most eyespots
B. Peacock's with eyespots covered
C. Female peacocks with eyespot sticks on their feathers
D. Using the same scientist to interact with the animals
Answer: While using the same scientist to interact with the animals would be a nice control, it is not the control GROUP. The control group generally remains unchanged so that the experimental results can be compared. In this case, a male peacock with spot's covered up could serve as an excellent control--it gives a baseline look at what female interest looks like without the spots.
📄 Study AP Biology, Unit 8.1 Responses to the Environment

3. A group of the same species, living in the same area at the same time can be described as a:
A. population
B. community
C. ecosystem
D. social group
Answer: Ecologists organize components of the biotic and abiotic components around us from smallest unit to largest. Smallest being the individual, and largest the biosphere. A population contain the same species at the same time in the same place. A community include other species living in the area, an ecosystem includes the biotic AND abiotic factors in the area.
📄 Study AP Biology, Unit 8.3: Population Ecology

4. Which of the following is NOT an abiotic factor that shapes ecosystems?
A. fire
B. rainfall
C. soil minerals
D. predators
Answer: Abiotic refers to the Nonliving components of an ecosystem such as climate, water, soil, etc. Predators are living and therefore biotic.
📄 Study AP Biology, Unit 8.7: Disruptions to Ecosystems

5. Animals communicate using a variety of methods. Which example best illustrates tactile communication?
A. frog calling
B. chimpanzee grooming
C. bee "waggle" dance
D. pheromones
Answer: Tactile communication refers to communication through touch like when chimpanzees physically tough each other during grooming. The waggle dance is something bee's see (visual cue), frog calling (audible signals), and pheromones (chemical signals).
📄 Study AP Biology, Unit 8.1: Responses to the Environment

6. Smaller organisms tend to have a higher relative metabolic rate compared to larger organisms. The relationship between body mass and metabolic is:
A. positive
B. direct
C. indirect
D. no relationship
Answer: If smaller organisms have a high metabolic rate, and large organisms have a slower metabolic rate, imagine plotting body mass on the x-axis of a graph and metabolic rate on the y-axis. As body mass increases, metabolic rate decreases. This is an indirect or negative relationship.
📄 Study AP Biology, Unit 8.1: Responses to the Environment

7. Unlike endotherms, ectotherms cannot utilize an internal system of maintaining body temperature. What best describes a way that an ectotherm can stay warm?
A. change behavior and move onto a warm rock in the sun
B. vasoconstriction to prevent heat loss
C. increasing metabolism to generate thermal energy
D. dilate blood vessels to increase heat dissipation
Answer: Without an internal mechanism to maintain body temperature like increasing/decreasing metabolism or vasodilation/constriction to generate heat or cool off (respectively) ectotherms must use their behavior to adjust body temperature.
📄 Study AP Biology, Unit 8.1: Responses to the Environment

8. A change in energy availability can disrupt an entire ecosystem. If a primary producer like phytoplankton declined drastically in number, what would result?
A. collapse of the last trophic level
B. primary producers increase to make up for the loss
C. increase in primary consumers and decrease in secondary consumers
D. Decline in primary and secondary consumers
Answer: Phytoplankton make up the first trophic level in an aquatic ecosystem, as they use photosynthesis to build organic molecules. If they decline, primary consumers will also decline because they rely on the producer (phytoplankton) as their energy source. If primary consumers decline, the next trophic level would also decline.
📄 Study AP Biology, Unit 8.2: Energy Flow Through Ecosystems

9. Autotrophs: heterotrophs
A. consume energy: capture energy from the sun
B. capture energy from the sun: capture energy from other organisms
C. produce ATP: use ATP
D. capture energy from consuming organism: use photosynthesis to make sugars
Answer: Autotrophs can "automatically" eat by capturing energy from the sun (photosynthesis) or from small inorganic molecules in the environment (chemosynthesis). Heterotrophs get energy from consuming other organisms and metabolizing lipids, carbohydrates, and proteins.
📄 Study AP Biology, Unit 8.2: Energy Flow Through Ecosystems

10. Carrying capacity depends on abiotic and biotic factors. As a population that grows and eventually reaches carrying capacity, the graph generally looks like a:
A. horizontal line
B. J
C. S
D. none of these
Answer: Although carrying capacity can be shown as a horizontal line to indicate the "limit" of the population size or growth, the actual graph of a population growing until it reaching carrying capacity looks like the letter S.
📄 Study AP Biology, Unit 8.3: Population Ecology

11. If the population size is 200 and r=0.10, calculate the change in population size (dN/dT= rN)
A. 20
B. 220
C. 2000
D. 2020
Answer: Multiplying 0.10 by the population size (200) yield 20. So, 20 new individuals were added to the population. The question does not require the extra step of determining the new population size, only the rate of change (dN/dt)
📄 Study AP Biology, Unit 8.3: Population Ecology

12. In a population of 100 individuals, calculate "r" if 10 offspring are born and 5 individuals die.
A. 0.05
B. 0.15
C. 6
D. 20
Answer: dN/dt refers to population growth and can be found by subtracting the deaths from births (dN/dt = B-D) 10-5= 5. Use dN/dt=rN to find "r". N is 100. (dN/dt)/(N)= r . 5/100= 0.15
📄 Study AP Biology, Unit 8.3: Population Ecology

13. Why can invasive species do so well in a new environment?
A. outcompete others by exploring a new niche
B. lack of predators
C. low competition
D. all of these
Answer: Invasive species are not-native to the area meaning they are from a completely different ecosystem. Humans can play a role in intentionally or unintentionally introduce invasive species to an ecosystem. Because it is a completely new ecosystem for the invasive species it can exploit new niches that often present low competition, low predation, and increased access to resources allowing them to outcompete other organisms.
📄 Study AP Biology, Unit 8.7: Disruptions to Ecosystems

14. According to the Simpson's Diversity Index, which two factors indicate a stable and diverse community?
A. species richness
B. number of species living in the community
C. number of individuals living in the community
D. number of species and abundance of individuals in each species
Answer: Even though the equation for Simpson's Diversity Index will be provided for you, it is important to know how to apply it. A community with many different species types has high species richness. The diversity index takes into account the richness (number of different species) and the number of organisms quantified for each species type.
📄 Study AP Biology, Unit 8.6: Biodiversity

15. A possible disadvantage to an ecosystem with low species diversity:
A. lower reproductive success
B. more resilient to change in environment
C. higher risk of predation
D. higher risk of disease spread
Answer: Relatively speaking, species diversity and community stability illustrate a direct relationship. Higher diversity allows for increased resilience to a changing environment (higher stability).
📄 Study AP Biology, Unit 8.6: Biodiversity
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