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Water, Carbon, and Nitrogen Cycle

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Name three important needs for water.

1. Habitat for many species of plants, animals, and microorganisms, 2. Most abundant substance in living organisms or things, 3. Important for biochemical mechanisms: digestion, cellular respiration

How is water distributed through the biosphere?

Water is distributed in a cycle called the water (hydrologic) cycle.

What draws water back to the earth?

Precipitation and gravity draws the water back in the form of rain, sleet, and snow.

What is transpiration?

When water is absorbed by the roots of a tree and used in photosynthesis, but it is lost from their leaves by evaporation.

What determines which plants grow where?

The amount of precipitation received by an area.

What is an aquifer?

The water-saturated zone of soil and rock where water from land enters the ocean.

Name two ways water travels from land to enter the ocean.

1. Seepage from the ground, 2. Runoffs from the surface.

What does runoff include?

The flow from rivers, melting snowfields, and glaciers.

How much water enters the hydrologic cycle?

Over 80%

How much water falls back as rain?

About 52%

What are macronutrients?

They are used by organisms in large quantities and they are nutrients that are composed of carbon, hydrogen, oxygen, nitrogen, and phosphorus.

What are micronutrients?

They are used only in small amounts and they are nutrients that are composed of iodine, iron, since, and other minerals.

What is the role of each of the following in the carbon cycle (primary producers, secondary producers, and decomposers)?

Primary producers: create their own food (i.e. plants) Secondary producers: eat the animals that eat autotrophs (i.e. snakes) Decomposers: eat dead animals (i.e. worms)

Where is most of the Earth’s carbon located and in what form?

The atmosphere in the form of carbon dioxide.

How does carbon enter the biotic part of the ecosystem?

Photosynthesis

What function do plants have in the forest in the carbon cycle?

Plants take the carbon in carbon dioxide and fix it in organic compounds such as glucose, starch, cellulose, and other carbohydrates

How is carbon dioxide returned to the atmosphere?

Respiration in plants

What is a primary producer?

All autotrophs (plants)

What happens when primary and secondary producers die?

Their organic matter enters the soil through the process of decay

What do detritus feeders contribute to the carbon cycle?

breaking down or living on decaying matter which release the material back into the environment and in respiration

What is a fossil fuel?

high pressure and temperature transform carbon-containing organic matter into coal, oil, and natural gas

How does carbon get in the oceans?

the air dissolves into the oceans.

What percent of the air is nitrogen?

about 78%

Why is nitrogen essential to life?

Because it is a key component of amino acid (building muscle) and nucleic acids

How do plants and animals get nitrogen if not from the atmosphere?

They get it through nitrogen fixation

What is nitrogen fixing bacteria?

These are legumes and symbiotic bacteria that are associated with their root nodules that convert nitrogen in the soil to ammonia

What is a major reservoir for ammonia?

Soil

Why do herbivores need nitrogen?

It is used for the synthesis of key organic compounds such as amino acid, protein, and nucleic acids.

What is denitrification?

The process of nitrates in the soil that are broken down by the microscopic bacteria, fungi, and other organisms which releases nitrogen into the atmosphere.

What is phosphorus an important biological molecule?

1. it is a part of adenosine triphosphate and the coenzyme NADP which is used in cellular processes, 2. It is present in sugar-phosphate backbone of nucleic acids, 3. It is essential element in phospholipids which make up the cell membrane.

What happens to phosphorus that erodes from rock and soil?

It dissolves and washes into rivers and streams or unites with oxygen to form phosphate and enters a major body of water.

How are phosphates incorporated into the organic molecules in plants and animals?

Plants grow near masses of water and the water gives up the phosphate which are absorbed by plants. Phosphates also enter the soil along the margins of the lake. Dissolved phosphate is readily absorbed by the roots of the plants, and then incorporated into organic molecules.

What happens to the phosphates when plants and animals die?

Phosphates return to the water and the plants that line the lake and absorb it and it enters the cycle again

What happens to the phosphorous that is carried by runoff to the oceans?

It concentrates in the marine sediment and some is eventually incorporated into the bodies of marine animals.

How are phosphates incorporated into the organic molecules in aquatic plants and animals?

Primary producers in the ocean incorporate phosphate into organic compounds. Other marine vertebrates eat these autotrophs like sea birds eat the fish and return phosphates into the ocean in the form of excrement.

What is different about the phosphorous cycle as compared to the water, carbon, and nitrogen cycles?

The atmosphere is not involved. For phosphate to leave the organic environment, there must be a process through which once-submerged sedimentary rock rich in phosphate is exposed because of the movement of the Earth’s plates. This rock enters the land and begins to weather.

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