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MCAS Plant questions from the Biology MCAS

February 2018

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31. A plant species growing along a coast produces seeds with fluffy hair-like
fibers on one end. A seed from one of the plants is shown below:

Seed fluffy fiber

Some of these seeds were dispersed by the wind to islands off the coast, where new plants grew. Within 10 years, the seeds of the island plants were different
from the seeds of the mainland plants. Compared to the mainland seeds, the
island seeds were heavier and had shorter hair-like fibers. Which of the following statements best explains why heavier seeds with shorter fibers were favored in the island environment?

A. These seeds carried more genes than the mainland seeds did.
B. These seeds were less likely to be blown off the island by wind.
C. The island plants needed to prevent animals from eating the seeds.
D. The island plants used more energy to produce heavy seeds than to grow.


33. Students investigated the effect of acid rain on photosynthesis. Several plants
were given water with a pH of 4 each day for two months. The results showed
that the plants had a reduced rate of photosynthesis.

How did the acidic water most likely reduce the plants’ rate of photosynthesis?

A. by storing excess oxygen produced by the plants
B. by changing the effectiveness of enzymes in the plants
C. by causing root hairs to grow on the roots of the plants
D. by increasing the amount of carbon dioxide taken in by the plants


34. Waxes form a waterproof coating over the stems and leaves of many terrestrial plants. The waxes are composed of fatty acids linked to long-chain alcohols. Based on this information, waxes are which type of organic molecule?

A. lipids .  B. nucleotides .  C. polysaccharides .  D. proteins


37. Maltose is a carbohydrate molecule that provides energy to plants early in their
life cycle. Which elements are most common in a molecule of maltose?

A. carbon and hydrogen
B. copper and nitrogen
C. iron and phosphorus
D. magnesium and sulfur


Algae, and the scientific method

The rate of photosynthesis in organisms depends in part on the wavelength of visible light. In the late 1800s, Thomas Engelmann demonstrated the relationship between the wavelength of light and the rate of photosynthesis. His experiment is described below.

• Engelmann used a prism to produce a visible light spectrum of violet, blue, green, yellow, orange, and red light.
• He shined the light spectrum onto cells of the algae Spirogyra.
• Once the light was shining on the Spirogyra cells, Engelmann added aerobic bacteria to the system. Aerobic bacteria need oxygen to live and grow.
• After adding the bacteria, Engelmann observed the regions of the light spectrum where the bacteria concentrated around the Spirogyra cells.

The setup and results of Engelmann’s experiment are represented by the diagram below:

Engelmann’s experiment Spirogyra algae spectrum prism

Mark your answers to multiple-choice questions 8 through 11 in the spaces provided in your Student Answer Booklet. Do not write your answers in this test booklet, but you may work out solutions to multiple-choice questions in the test booklet.

8. Why are the greatest numbers of aerobic bacteria found at the 400–500 nm and 600–700 nm wavelengths of light?

A. Photosynthesis rates are highest there, producing large amounts of water.
B. Photosynthesis rates are highest there, producing large amounts of oxygen.
C. Photosynthesis rates are lowest there, producing small amounts of glucose.
D. Photosynthesis rates are lowest there, producing small amounts of carbon dioxide.

9. What is the role of visible light when Spirogyra cells perform photosynthesis?
A. It provides the energy for the photosynthesis reaction.
B. It concentrates the photosynthesis products for export.
C. It activates the DNA that directs the photosynthesis reaction.
D. It transports photosynthesis reactants across the cell membrane.

10. What is exchanged between the Spirogyra and the bacteria in
Engelmann’s experiment?

A. DNA and RNA
B. starch granules and spores
C. chlorophyll and cytoplasm
D. oxygen and carbon dioxide

11. A scientist used Engelmann’s data to predict how the concentrations of different substances in and around Spirogyra cells will change when the cells are exposed to different wavelengths of light. A graph for one substance is shown below.

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What is represented on the y-axis?

A. chlorophyll concentration .        B. hydrogen concentration
C. oxygen concentration .        D. water concentration


Spring 2018 MCAS

3. All corn plants contain the ZmLA1 gene. Some corn plants contain a certain mutation in the ZmLA1 gene. The graph below shows the amount of ZmLA1 RNA produced in plants with the normal gene and in plants with the mutated gene.

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Based on the graph, what most likely happens in corn plant cells as a direct result of the mutated gene?

A. DNA replication increases.
B. Lipid production decreases.
C. Glucose synthesis increases.
D. Protein production decreases.


4. The growth of plants in many ecosystems is limited by the supply of
nitrogen. Which of the following groups of organisms plays the largest role in
moving nitrogen between the atmosphere and plants?

A. bacteria .      B. earthworms .      C. insects .    D. protists


7. Lithops are multicellular organisms found in sandy soil in deserts. They
have large, central vacuoles in their cells that store water. Which of the following best classifies lithops?
A. They are bacteria because they store water.
B. They are animals because they are multicellular.
C. They are fungi because they are found in sandy soil.
D. They are plants because they have large, central vacuoles.


14. There are many fungus species that live inside plant tissues. What determines
whether the relationship between a fungus and a plant is commensalism,
mutualism, or parasitism?

A. where the fungus is located in the plant
B. how long the fungus survives in the plant
C. whether the fungus reproduces in the plant with spores, seeds, or runners
D. whether the effect of the fungus on the plant is neutral, positive, or negative


37. Plants in floodplains often get covered by water during floods. Some
plants survive the floods because they can continue photosynthesis
underwater. However, the plants’ rates of photosynthesis are much lower
underwater than above water.

Which of the following helps to explain why the rates of photosynthesis are
lower underwater than above water?

A. There is too much oxygen in the water.
B. There is no carbon dioxide in the water.
C. The chloroplasts do not function underwater.
D. The available light is less intense underwater.


February 2017

17. Carbon fixation is an important part of the carbon cycle. Carbon fixation is the conversion of carbon dioxide into organic compounds such as glucose. Which of the following organisms cannot fix carbon?

A. grass
B. green algae
C. mushrooms
D. oak trees


3. A botanist studied two groups of rice plants to determine how they are related. Both groups of plants have similar shapes, but one group has longer stalks. When the botanist cross-pollinated plants from one group with plants from the other group, the seeds produced did not sprout or grow.

Which of the following conclusions is best supported by this information?

A. The two groups are the same species because the plants have similar shapes.
B. The two groups are different species because they have differently sized stalks.
C. The two groups are different species because the seeds produced cannot sprout or grow.
D. The two groups are the same species because the plants were cross-pollinated and produced seeds


20. A partial food web is shown below. Which organisms in the food web are both primary and secondary consumers?

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A. bluegills
B. cattails
C. coyotes
D. snakes


28. A student looks at a cell under a microscope. Which of the following
observations would indicate that the cell is from a plant rather than an animal?

A. a nucleus located inside of the cell
B. numerous cilia on the outside of the cell
C. chloroplasts in the cytoplasm of the cell
D. a thin membrane around the edge of the cell


30. Prolonged periods of drought in an area cause decreases in plant population
sizes. Which of the following statements describes how the decreases in plant
population sizes then affect other populations in the area?

A. Omnivore population sizes increase, and herbivore population sizes increase.
B. Omnivore population sizes decrease, and carnivore population sizes increase.
C. Herbivore population sizes increase, and carnivore population sizes decrease.
D. Herbivore population sizes decrease, and carnivore population sizes decrease.

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