AP Biology : Understanding Eco-Chemical Cycles

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #51 : Ecology

Which of the following types of soil bacteria convert ammonia into nitrate molecules during nitrification?

Possible Answers:

Saprobiotic bacteria

Nitrifying bacteria

None of these

Denitrifying bacteria

Correct answer:

Nitrifying bacteria

Explanation:

Nitrification takes place in the soil and is the process in which ammonium is converted into nitrate. Nitrifying bacteria facilitate this process.

Example Question #52 : Ecology

Which of the following sets of two nitrogen cycle processes involve atmospheric nitrogen?

Possible Answers:

Ammonification and nitrification

Denitrification and nitrogen fixation

Nitrification and denitrification

Ammonification and nitrogen fixation

Correct answer:

Denitrification and nitrogen fixation

Explanation:

The processes of denitrification and nitrogen fixation both involve atmospheric nitrogen. Nitrogen fixation is the conversion of atmospheric nitrogen into ammonia and organic nitrogen by nitrogen fixing bacteria. In denitrification, denitrifying bacteria convert nitrates into nitrogen gas, which is released into the atmosphere.

Example Question #53 : Ecology

In the process of denitrification, which of the following forms of nitrogen is returned to the atmosphere?

Possible Answers:

Nitrate

Ammonium

Nitrogen gas

Nitrite

Correct answer:

Nitrogen gas

Explanation:

Denitrification is the final process of the nitrogen cycle in which soil-dwelling denitrifying bacteria convert nitrates back into nitrogen gas. The nitrogen gas is released back into the atmosphere.

Example Question #54 : Ecology

Which of the following is an alternative source of natural nitrogen in ecosystems?

Possible Answers:

Shells

None of these

Lakes

Bedrock

Correct answer:

Bedrock

Explanation:

An alternative source of naturally occurring nitrogen in ecosystems is bedrock. Bedrock is nitrogen rich and can be broken down to act as a nitrogen source.

Example Question #55 : Ecology

Which of the following best explains how atmospheric nitrogen enters the nitrogen cycle in marine ecosystems?

Possible Answers:

Through animal excretions

Through precipitation

Through plant decomposition

Through algae waste

Correct answer:

Through precipitation

Explanation:

The marine nitrogen cycle is very similar to the terrestrial nitrogen cycle. In marine ecosystems, atmospheric nitrogen enters the cycle through precipitation.

Example Question #56 : Ecology

Which of the following best describes the overall impact of humans on the nitrogen cycle?

Possible Answers:

Slight decrease in nitrogen

Increase in nitrogen

Depletion of nitrogen

Sequestered nitrogen

Correct answer:

Increase in nitrogen

Explanation:

Human activities such as chemical fertilizers, industrialization, and pollution significantly increase the amount of nitrogen that is biologically available in an ecosystem.

Example Question #52 : Ecology

Beyond bacteria, which of the following acts as an alternative method for nitrogen fixation?

Possible Answers:

Fertilizers 

Lightening strike

Earthquake

Roots

Correct answer:

Lightening strike

Explanation:

An alternative method of nitrogen fixation is a lightening strike; however, this is rare and soil-dwelling bacteria perform most of the Earth’s nitrogen fixation.

Example Question #58 : Ecology

Which of the following best represent stages of the water cycle?

Possible Answers:

Precipitation

Evaporation

Condensation

All of these

Correct answer:

All of these

Explanation:

The correct answer is “all of these.” The water cycle can be broken down to three stages. The three stages of the water cycle are evaporation, condensation, and precipitation.

Example Question #59 : Ecology

Water exists in which of the following states of matter during the water cycle?

Possible Answers:

Solid, liquid, and gas

Solid and gas

Gas and liquid

Only solid

Correct answer:

Solid, liquid, and gas

Explanation:

During the water cycle, water can take three forms: liquid, solid, and gas.

Example Question #60 : Ecology

Which of the following is true regarding water on Earth?

Possible Answers:

Climate has no impact on the water cycle

Water exists in two forms on Earth: solid and liquid

Water is sequestered in reserves

The amount of water on Earth is far from constant

Correct answer:

Water is sequestered in reserves

Explanation:

The water cycle describes the movement of water on Earth. The amount of water is relatively constant; however, it is subject to fluctuations based on climatic conditions. Water exists in three forms in the water cycle: solid, liquid, and gas. On Earth, water is sequestered in different reserves including ice, oceans, and the atmosphere.

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