The Cycling of Materials in Ecosystems As energy

The Cycling of Materials in Ecosystems • As energy and matter flow through an ecosystem, matter must be recycled and reused. • Substances such as water, carbon, nitrogen, calcium, and phosphorus each pass between the living and nonliving worlds through biogeochemical cycles.

The Cycling of Materials in Ecosystems • In biogeochemical cycles, interactions of organisms and their environments continuously recycle these elements. • If not for this worldwide recycling program, supplies of essential elements would have been depleted as they became bound in the bodies of organisms that lived eons ago.

Water cycle • The water cycle moves water from the ocean to the atmosphere, onto land, and back to the oceans. • Three important processes in the water cycle are evaporation, transpiration, and precipitation.

Water cycle • The water cycle moves water from the ocean to the atmosphere, onto land, and back to the oceans. • The arrows identify processes that move water.

Water cycle • Evaporation adds water as vapour to the atmosphere. Heat causes water to evaporate from bodies of water, from the soil, and from the bodies of living things. • The process by which water evaporates from the leaves of plants in terrestrial ecosystems is called transpiration. Transpiration causes plants to take in water through their roots to replace the water that is being lost through their leaves. • Animals drink water or obtain it from their food. They release this water when they breathe, sweat, or excrete.

Water cycle • Water leaves the atmosphere through precipitation. The amount of water the atmosphere can hold depends on abiotic factors, such as temperature and air pressure. Once the atmosphere becomes saturated with water vapor, precipitation occurs in the form of rain, snow, hail, or fog.

Water cycle • The movement of water causes the movement of other nutrients. Carbon, nitrogen, and phosphorus all have soluble forms that can be moved from place to place by flowing water. As water trickles through soil, it carries nutrient particles from topsoil into deeper soil layers.

Carbon cycles • The carbon cycle is a series of processes which keep the amount of carbon in the form of carbon dioxide in the air at a relatively constant level. • The element carbon is essential to all living organisms because carbon is the major ingredient of all organic molecules (carbohydrates, fats and proteins) which make up living tissue.

Carbon cycles • Photosynthesis removes carbon dioxide (CO 2) from the atmosphere and incorporates it into organic molecules, which are passed along the food chain by consumers. • Cellular respiration by producers and consumers returns CO 2 to the atmosphere. • Decomposers break down the carbon compounds in detritus; that carbon, too, is eventually released as CO 2.

Carbon cycles • On a global scale, the return of CO 2 to the atmosphere by cellular respiration closely balances its removal by photosynthesis. • However, the increased burning of wood and fossil fuels (coal and petroleum) is raising the level of CO 2 in the atmosphere. This increase in CO 2 is leading to significant global warming.

Human Influences on the Carbon Cycle • In the last 150 years, the concentration of atmospheric carbon dioxide has risen more than 30 percent. • Humans contribute to this increase by burning fossil fuels and other organic matter. • Our industrial society depends on the energy released by the burning of fossil fuels—coal, oil, and natural gas.

Human Influences on the Carbon Cycle • Burning releases the energy in these molecules, but it also releases carbon dioxide. • When large areas of forest are burned each year to clear land for agriculture, less vegetation remains to absorb carbon dioxide from the atmosphere through photosynthesis.

Human Influences on the Carbon Cycle • In 2007, the Intergovernmental Panel on Climate Change reviewed the results of many scientific studies related to climate change. • The panel of hundreds of scientists from all over the world concluded that the warming in recent decades is very likely due to a human-induced increase in atmospheric greenhouse gases. • Unlike other possible factors, the rise in greenhouse gases correlates well with the rise in temperature.

Photosynthesis • The foods made by green plants are energyrich substances called carbohydrates. Examples of carbohydrates are starch and sugar. When such foods are broken down, they release a lot of energy for the plants to grow and reproduce. • Photosynthesis is the process by which food is made in plants, from water and carbon dioxide. This process can only occur in the presence of chlorophyll and sunlight.

Photosynthesis • The word equation for photosynthesis is given below. The conditions for photosynthesis are written above and below the arrow.

• Chlorophyll is a green pigment found in the chloroplasts of plant cells. It absorbs the energy from the Sun (sunlight) and uses that energy to convert carbon dioxide and water into sugar and other carbohydrates

Photosynthesis • The raw materials (reactants) for photosynthesis are: • Carbon dioxide: This is found in the air and enters the underside of the leaves through tiny pores (called stomata). • Water: This is taken in mainly through the roots and transported up the plant to the leaves due to transpiration.

Photosynthesis • The output materials (products) of photosynthesis are: • Glucose: This is found in the form of simple sugar, which can be used to produce energy or can be stored as starch. • Oxygen: A gas important to living things which is released into the air.

Photosynthesis • Many plants convert the glucose produced during photosynthesis into starch. This is stored in the leaves and indicates photosynthesis has taken place. A test for the presence of starch is that iodine solution will turn blue-black if starch is present.

Photosynthesis • The best conditions for photosynthesis are warm and humid conditions. Photosynthesis depends on reactions of enzymes in the chloroplasts. Enzymes work best around 30 °C — 35 °C. Humid conditions provide water, which is one of the raw materials of photosynthesis.

Photosynthesis • The energy change during photosynthesis involves light energy (from the Sun) being converted into chemical potential energy of glucose or starch. This energy is later released during the process of respiration which takes place in both plants and animals.

Nitrogen Cycle

Nitrogen Cycle • Nitrogen is essential for the formation of amino acids in proteins. The nitrogen cycle is a model that explains how nitrogen is recycled. • There's lot of nitrogen in air – about 78% of the air is nitrogen. Because nitrogen is so unreactive, it cannot be used directly by plants to make protein. • Only nitrates are useful to plants, so we are dependent on other processes to convert nitrogen to nitrates in the soil.

• Nitrogen gas is converted to nitrate compounds by nitrogen-fixing bacteria in soil or root nodules.

• Lightning also converts nitrogen gas to nitrate compounds. The Haber process converts nitrogen gas into ammonia used in fertilizers.

• Ammonia is converted to nitrates by nitrifying bacteria in the soil.

• Plants absorb nitrates from the soil and use these to build up proteins. The plant may be eaten by an animal, and its biomass used to produce animal protein.

• Urea and egested material is broken down by decomposers. This results in nitrogen being returned to the soil as ammonia.

• Decomposers also break down the bodies of dead organisms resulting in nitrogen being returned to the soil as ammonia.

• In some conditions denitrifying bacteria in the soil break down nitrates and return nitrogen to the air. This is usually in waterlogged soil. Improving drainage reduces this effect, making the soil more fertile.

Simplified nitrogen cycle

Nitrogen Cycle

Decomposers • Bacteria and fungi • Organism that feeds on biological remains and breaks organic material down into its inorganic subunits. • They get their energy from dead organisms apart from animal and plant waste products.

Detritivores • Worms, millipedes, sea stars, crabs and dung flies • Consumer that feed on small bits of organic material. • They perform an additional function which is to return essential nutrients back to the ecosystem in the process.

Decomposers vs Detritivores • Both aid in decomposition of dead or decaying matter. • Decomposition (or decay) is a chemical reaction where a complex compound is broken down into simpler compounds. • Detritivores help in producing essential nutrients. Worms are also called scavengers as they eat up skin of an apple leaving the inside of the fruit for other decomposers.

Decomposers vs Detritivores • Both get energy from decaying matter • But detritivores actually eat organic matter, while decomposers secrete enzymes to digest organic matter and then absorb resulting molecules. • Decomposers are smaller organisms while detritivores are larger organisms.

Decomposers vs Detritivores • In essence, decomposers such as bacteria and fungi cause decay at a microscopic level. Other larger organisms, called detritivores, help speed up decay by feeding on detritus – dead and decaying material. They break it down into smaller pieces, so increasing the surface area for the bacteria and fungi. •