III. Cycles of Matter *While energy is crucial to an ecosystem, all organisms need water, minerals, and other life-sustaining compounds to survive. In most organisms, more than 95% of the body is made up of oxygen, carbon, hydrogen, and nitrogen that must be broken down into a chemical form that the cells can take up. A. Recycling in the Biosphere *Energy and matter move through the biosphere very differently. Matter is recycled within and between ecosystems. Elements, compounds, and other forms of matter are passed through biogeochemical cycles that connect the biological, ecological, and chemical aspects of the biosphere.

Cycles of Matter -Matter cycles over and over again through the biosphere because biological systems don’t use up matter but transform it. It is assembled into living tissue or passed out of the body as waste products. B. The Water Cycle -The water that living things need to survive moves between the ocean, atmosphere, and land.

The Water Cycle Entering the atmosphere – water molecules enter the atmosphere as water vapor (a gas) when they evaporate from the ocean, other bodies of water, or when they evaporate from the leaves of plants. Evaporation – the process by which water changes from liquid form to an atmospheric gas. Transpiration – loss of water from a plant through its leaves of plants.

The Water Cycle Leaving the atmosphere – the sun heats the atmosphere throughout the day, causing warm, moist air to rise and cool. The water vapor condenses into tiny droplets that form clouds. Once large enough, the water droplets fall to the surface in the form of precipitation : rain, snow, sleet, hail, etc. Traveling on the surface – most precipitation runs along the surface of the ground until it enters a river or stream that carries the runoff back to an ocean or lake. Some rain will seep into the soil and become ground water. Water in the soil enters plants through the roots, restarting the cycle.

C. Nutrient Cycles Nutrients – all the chemical substances that an organism needs to sustain life (chemical “building blocks” that come from food). -Every living organism needs nutrients to build tissues and carry out essential life functions. Like water, nutrients are passed between organisms and the environment through biogeochemical cycles.

3 Major biogeochemical cycles 1. Carbon cycle – cycle that moves carbon through the biosphere. Carbon is found in several large reservoirs in the biosphere : in the atmosphere as CO 2 gas, in the oceans as dissolved carbon dioxide, on land in organisms, rocks, and soil, & underground as coal, petroleum, and calcium carbonate rock.

The Carbon Cycle Carbon’s role in the biosphere : Makes up living tissue & animal skeletons Makes up rock It forms CO 2 gas in the atmosphere Carbon dioxide is taken in by plants during photosynthesis and is given off by both plants and animals during respiration.

Four main types of processes move carbon through its cycle : Biological processes, such as photosynthesis, respiration, and decomposition, take up and release carbon and oxygen. Geochemical processes, such as erosion and volcanic activity, release carbon dioxide to the atmosphere and oceans. Mixed biogeochemical processes, such as the burial and decomposition of dead organisms and their conversion under pressure into coal and petroleum (fossil fuels), store carbon underground. Human activities, such as mining, cutting and burning forests, and burning fossil fuels, release carbon dioxide into the atmosphere.

The Nitrogen Cycle 2. Nitrogen Cycle – cycle that moves nitrogen through the biosphere. The atmosphere is the main reservoir of nitrogen in the biosphere (78% of the atmosphere). It also cycles through the soil and through the tissues of living organisms. Nitrogen’s role in the biosphere : All organisms need nitrogen to make amino acids, which are used to build proteins.

How nitrogen moves through the biosphere : Nitrogen gas from the atmosphere is taken in by bacteria in the soil/on the roots of plants and converted into ammonia. Nitrogen fixation – process of converting nitrogen gas into ammonia. Other bacteria in the soil convert ammonia into nitrates and nitrites.

How nitrogen moves through the biosphere : Producers use nitrates and nitrites to make proteins. Consumers eat the producers and reuse the nitrogen to make their own proteins. When organisms die, decomposers return nitrogen to the soil as ammonia for producers to use. -Some soil bacteria release nitrogen into the atmosphere by denitrification converting nitrates into nitrogen gas.

The Phosphorous Cycle 3. Phosphorous Cycle – cycle that moves phosphorous through the biosphere. Phosphorous in the biosphere cycles among the land, ocean sediments, and living organisms. Although important, it is not common because it doesn’t enter the atmosphere. It is mostly within rock and soil minerals on land, and in ocean sediments. Phosphorous’ role in the biosphere : Phosphorous is essential to living organisms because it forms part of important life-sustaining molecules such as DNA and RNA.

How phosphorous moves through the biosphere : Rocks and sediments wear down, releasing phosphate – some phosphate stays on land and cycles between organisms and the soil. -When plants absorb phosphate from the soil or from water, the plants bind the phosphate into organic compounds, which move through the food web from producers to consumers to the rest of the ecosystem.

How phosphorous moves through the biosphere : Phosphate washes into rivers & streams & dissolves. Phosphate makes its way to the ocean, where it is used by marine organisms.

D. Nutrient Limitation *One key point of interest to ecologists is primary productivity – the rate at which organic matter is created by producers. -One factor that controls the primary productivity of an ecosystem is the amount of available nutrients. If a nutrient is in short supply, it will limit an organism’s growth. When an ecosystem is limited by a single nutrient that is scarce or cycles very slowly it is referred to as a limiting nutrient.

D. Nutrient Limitation *The ocean is nutrient-poor compared to the land and when aquatic ecosystems receive large amounts of a limiting nutrient (ex : runoff from heavily fertilized fields)algae & other producers increase quickly and can lead to algal blooms which can disrupt ecosystem equilibrium.