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AP®BiologyCollege BoardExam QuestionsUnit 8: EcologyEcosystems

Ecosystems (College Board AP® Biology): Exam Questions

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11 mark

In an aquatic ecosystem, phytoplankton serve as primary producers. Zooplankton consume phytoplankton, small fish consume zooplankton, and large fish prey on small fish.

What would be the expected outcome if phytoplankton populations suddenly declined?

  • Zooplankton populations would increase due to reduced competition.

  • Small fish populations would remain stable because they do not rely on phytoplankton directly.

  • Zooplankton, small fish, and large fish populations would all decline over time.

  • Large fish populations would increase due to decreased competition with small fish.

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A group of migratory birds stops in a wetland to feed before continuing their journey. The birds may be unable to find enough food to meet their energy demands.

Which of the following is the most likely consequence of this happening?

  • They will store excess energy as fat and gain mass.

  • They will maintain their current body mass without changes.

  • They will lose body mass and may not survive the migration.

  • They will increase their metabolic rate to compensate for energy loss.

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Many reptiles, such as lizards, bask in the sun during the morning and retreat to the shade in the afternoon.

What is the primary reason for this behavior?

  • To regulate their body temperature since they are ectothermic.

  • To increase their metabolic rate since they are endothermic.

  • To absorb more oxygen for cellular respiration.

  • To prevent dehydration by reducing water loss.

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Honeybees in a hive perform a waggle dance to communicate the location of a food source to other members of the colony.

This is an example of which type of response to an environmental change?

  • Physiological response

  • Behavioral response

  • Genetic adaptation

  • Structural adaptation

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Animals may use visual, auditory, and chemical signals which lead to changes in behavior. These signals can affect reproductive success.

Which of the following best explains how an animal uses signaling behavior to enhance reproductive fitness?

  • Animals may use random movement to determine the location of suitable environmental conditions, ensuring access to a food source.

  • The fight-or-flight response increases blood flow to the muscles, allowing prey organisms to run quickly.

  • Colorful flowers attract insect pollinators, increasing the transfer of pollen between flowers.

  • Animals may use scent marking to indicate the extent of a territory and deter other members of the same species.

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All living organisms need energy to maintain their tissues, grow and reproduce. Different groups of organisms rely on different modes of nutrition in order to gain energy.

Which of the following correctly describes mechanisms by which living organisms capture energy in ecosystems?

  • Heterotrophic and chemosynthetic organisms both gain their energy from the carbon compounds in other living organisms.

  • Photosynthetic organisms gain their energy from carbon compounds gained from the soil.

  • Chemosynthetic and photosynthetic organisms are examples of autotrophs.

  • Heterotrophic organisms produce their own organic molecules using inorganic substances.

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Certain species of male frogs produce mating calls to attract females. Researchers conducted an experiment measuring the success rate of males with different call patterns. The results are shown below:

Call type

Average number of mates gained

Short calls

3

Long calls

7

Based on the data, what is the most likely explanation for the reproductive advantage of long calls?

  • Long calls are energetically cheaper to produce, allowing males to conserve energy.

  • Long calls provide a stronger visual cue, making males easier to locate.

  • Long calls serve as an indicator of male fitness, increasing their attractiveness to females.

  • Long calls establish territorial boundaries and prevent competition between males.

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In response to seasonal temperature changes, different species have evolved unique strategies to survive harsh winter conditions. The table below describes adaptations observed in three species that experience extreme cold.

Species

Observed adaptation

Arctic fox

Thickening of fur and increased metabolic activity

Emperor penguin

Reduced blood flow to extremities, maintaining core body temperature

Brown bear

Decreased heart rate and metabolic slowdown during winter months

Which of the following best explains how these adaptations increase survival?

  • These adaptations are behavioral responses that allow the organisms to maintain thermoregulation.

  • Survival is maximized because all three species reduce metabolic activity during winter months, ensuring lower energy expenditure when resources are scarce.

  • These adaptations involve physiological responses, allowing the organisms to regulate internal conditions and maintain homeostasis in extreme environments.

  • By slowing metabolic processes, these adaptations reduce the need for food and water, allowing the species to survive with limited resources.

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Metabolic rate is the energy expended over time by an organism or cell. Researchers measured the metabolic rate of cells within a series of organisms of different body mass. They recorded the metabolic rate of the cells within the body of the organism (in vivo) and in a petri dish in the laboratory (in vitro). Their results are shown in Figure 1.

Scatter plot showing cellular metabolic rate vs body mass. Solid line indicates in vivo data; dashed line shows in vitro data. Key provided below graph.
Figure 1. The metabolic rate of cells for organisms of differing body mass, both in vivo and in vitro.

Which of the following claims is most likely to be correct for the data shown in Figure 1?

  • The cells of each species have a fixed metabolic rate that is determined by body mass.

  • Cellular metabolic rate is affected by external conditions as well as body mass.

  • Cellular metabolic rate is determined by nutrient availability.

  • Metabolic rate is determined by environmental conditions and is not affected by body mass.

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The life history strategy of a species includes factors such as age of reproduction, frequency of reproduction and number of offspring. One example of a life history strategy sometimes found in insect species is a period of suspended development known as diapause. One study looked at the relationship between mean daily temperature during larval development and entry into prolonged diapause (a period of diapause that lasts for a year or longer) in a species of moth. The results are shown in Figure 1 below.

Scatter plot showing individuals in prolonged diapause (%) versus mean larval development temperature (°C), with a downward curve peaking at 0°C and 12°C.
Figure 1. The effect of mean temperature during larval development on entry into prolonged diapause in moths

Which of the following provides the most likely explanation for the relationship between mean temperature and entry into prolonged diapause?

  • Increasing average global temperatures, due to climate change, are causing more moths to enter prolonged diapause.

  • Moth larvae enter prolonged diapause to reduce competition between surviving moths in future years.

  • Moth larvae enter prolonged diapause to save energy over multiple cold or warm seasons.

  • Moth larvae are less likely to enter diapause when mean temperatures are in between extremes of cold and warm.

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Plankton are small organisms that live in aquatic environments. Plankton can be photosynthetic (phytoplankton) or heterotrophic (zooplankton). A study measured the biomass of phytoplankton and zooplankton between July and May of a single year. The results of the study are shown in Figure 1.

Line graph showing monthly biomass (mg/l) of phytoplankton and zooplankton from July to May. Phytoplankton peaks in February, zooplankton in July.
Figure 1. Biomass of phytoplankton and zooplankton between July and May.

Which of the following are correct descriptions of the data in Figure 1?

  • Zooplankton biomass decreases by around 120 % between July and May.

  • Between July and December the zooplankton population experiences a net loss of energy.

  • The average rate of biomass growth in zooplankton between January and April is 11.7 mg l-1 month-1.

  • The average rate of biomass growth in zooplankton between January and April is -0.7 mg l-1 month-1.

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A freshwater lake ecosystem receives runoff from nearby farms; this increases the nutrients available in the water, which leads to rapid algal growth on the surface of the water (algal blooms).

Over time, researchers observe the following changes:

  • Oxygen levels in deeper water decline sharply

  • Fish populations decrease, in particular large predatory species

  • Decomposers increase in abundance

Which of the following best explains how disruptions in energy flow and nutrient cycling have contributed to these changes?

  • Increased decomposition of organic matter leads to oxygen depletion, and a reduction in energy transfer to higher trophic levels.

  • Increased primary productivity contributes to an increase in energy transferred through the food chain, resulting in fewer, larger fish due to competition.

  • Excessive autotrophic respiration increases competition for oxygen, aquatic organisms die leading to an increase in decomposition.

  • A decrease in photosynthesis in deep water plants limits energy transfer, increasing competition between primary consumers and forcing fish populations to migrate in search of food sources.

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