Nutrient Cycles

Science 10

Nutrient Cycles

The chemical elements that are used by organisms to build and operate their bodies are called nutrients

Nutrients

Organisms obtain nutrients from compounds that they absorb through the environment

The movement of nutrients through the environment are called nutrient cycles

Closed System

The earth is a closed system There is little or no input of materials from

outside the system

Biotic vs. Abiotic

Nutrients in the living organisms are considered a part of the biotic component of the environment

Nutrients in the non-living organisms are considered a part of the abiotic component of the environment

Why a cycle?

When an organism dies, the nutrients in its tissues are returned to the cycles

The Carbon Cycle

Recall that plants make carbohydrates (sugars) during the process of photosynthesis

Photosynthesis is one stage of the carbon cycle

Plants capture carbon from the atmosphere and combine it with water to make sugar

How does it get to animals?

When consumers eat the plants, the carbon compounds are broken down and recombined to build animal tissues

Thus, carbon is moved through the food chain!

Carbon dioxide (CO2)

Carbon dioxide makes up only 0.03% (by volume) of earth’s atmosphere – so why isn’t it all used up by plants?

Carbon dioxide is returned to the atmosphere through cellular respiration

Respiration breaks apart the energy rich carbohydrate molecules in cells and releases the carbon as carbon dioxide

When organisms release their wastes or die, decomposers such as bacteria and fungi release this carbon back into the cycle

The Carbon Cycle

Water World

Much of the carbon cycle actually takes place in aquatic ecosystems

In fact the world’s oceans and lakes hold over 50 times as much carbon as the atmosphere

Carbon dioxide dissolves at the surface of water to form carbonic acid which water plants use as their source of carbon

Other organisms such as crabs, shellfish, coral, etc use carbon to form their shells

When they die, these shells sink to the bottom to form thick layers that eventually harden into sedimentary rock, thus trapping the carbon for millions of years

Caption: Limestone with fossilized shells. This sedimentary rock has numerous shells, including many coiled turret shells from the Turritella species of snail, embedded within it. This kind of rock, made of a loose aggregate of shells or shell fragments, is known as a coquina.

Disrupting the carbon cycle

Over the centuries, the amount of carbon dioxide produced by cellular respiration has tended to equal the amount of carbon dioxide absorbed by photosynthesis

This balance can be changed, however, if large amounts of carbon are removed from or added to parts of the carbon cycle

During the carboniferous period, large amount of plant matter were buried under thick layers of sediment before it could be broken down

After millions of years the plant matter was compressed into coal and oil (fossil fuels)

When we burn these fossil fuels we release this carbon into the environment