Understanding Eco-Chemical Cycles - AP Biology

Industrialization has increased the burning of fossil fuels, such as coal and oil. This releases carbon from the geosphere into the atmosphere, increasing the carbon in the atmosphere. Carbon dioxide and methane are big contributors to the greenhouse effect and global warming.

Modern human activities greatly impact the carbon cycle. Increase in land usage decreases the presence of natural ecosystems and the ability of organisms to remove carbon from the atmosphere. Pollution damages organisms, which reenters the terrestrial biosphere and increases erosion. Deforestation directly removes carbon rom ecosystems and decreases the amount of carbon absorbed from the atmospheric biosphere.

The carbon cycle includes three levels: the geosphere, the terrestrial biosphere, and the atmospheric biosphere. The geosphere refers to the solid part of the earth, the terrestrial biosphere refers to all the living organisms on the land, and the atmospheric biosphere refers to the living organisms in space between the land and the outer ends of the atmosphere. Carbon is present in all levels and travels throughout the levels through various processes including photosynthesis, dissolution, and decay.

Nitrogen makes up most of the Earth’s atmosphere; however, this reserve of nitrogen is limited for biological use. Nitrogen exists in diatomic forms in the atmosphere and the process of nitrogen fixation frees atoms for biological use. As a result, nitrogen is a limiting resource in many ecosystems.

Nitrogen is necessary for all life; therefore, it is present in the territorial biosphere in living organisms, humus, and decomposing matter.

Nitrogen fixation can be described as the process in the nitrogen cycle in which bacteria “fix” atmospheric nitrogen into ammonia and usable forms of organic nitrogen.

In the process of assimilation, organic nitrogen is incorporated into plants through the roots. The type of nitrogen incorporated may be nitrate ions, nitrite ions, or ammonium ions. Symbiotic bacteria may assist this process.

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.

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.

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.

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

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

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.

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.

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

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.

Energy is needed for water to enter different stages of the water cycle (condensation, precipitation, and evaporation). This leads to a change in temperature.

The precipitation stage of the water cycle is when condensed water vapor falls to Earth. Precipitation exists in various forms that include rain, snow, and hail.

Infiltration is a process in the water cycle in which water moves from the ground’s surface into the soil. Subsurface flow is another process where water flows below the ground surface; therefore, the difference between the two is the origin of the flowing water.

Evaporation is one of three main stages of the water cycle. In this process, water changes phases from the liquid to the gas phase.