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 (CO 2 )  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