Home Random Page



Pyramids of productivity


There are a number of ways of looking at productivity in terms of energy pyramids.

All point out the significance of energy loss from one trophic level to the next, or decreasing energy transfer. Some sample pyramids are pyramid of productivity, pyramid of biomassand pyramid of numbers.


The pyramid of productivity is a fundamental method to show interaction of organisms at different trophic levels. It describes efficiency of energy transfer and productivity of food chains (the law of 10% of energy)

The pyramid of biomass shows the total biomass at each trophical level (producers-herbivores-carnivores ect). A pyramid of standing biomass will be energetically different from a pyramid of productivity.

The pyramid of numbers refers to a distribution of species at each trophical level. It can be direct (grass-rodent-owl) and upside down (spiders-beetles). Some ecosystems, looked at by numbers may be inverted relative to productivity pyramids.


There are tremendous differences in productivity in the different biomes. Temperature, precipitation and light intensity, availability, or lack of nutrients are all factors in productivity.

Nutrient or biogeochemical cycles in the ecosystem

Biogeochemistry is a term that is defined as the study of how living systems influence, and are controlled by, the geology and chemistry of the earth. Thus biogeochemistry encompasses many aspects of the abiotic and biotic world that we live in.


The energy moving through an ecosystem is chemical energy, so a second major process of any ecosystem is the movement of nutrients, both those directly providing fuel, as well as those providing for the structure and functioning of the organism. A biogeochemical cycle, or a nutrient cycleis a pathway by which a chemical element or molecule moves through both biotic (biosphere) and abiotic (lithosphere, atmosphere, and hydrosphere) compartments of Earth.There are two major cycles in the biosphere: geological (long-term time scale) and biotic (short-term time scale) cycles. The most well-known and important biogeochemical cycles, for example, include the carbon cycle, the nitrogen cycle, the oxygen cycle, the phosphorus cycle, the sulfur cycle, and the water cycle. There are many biogeochemical cycles that are currently being studied for the first time as climate change and human impacts are drastically changing the speed, intensity, and balance of these relatively unknown cycles. These newly studied biogeochemical cycles include the mercury cycle and the human-caused cycle of atrazine, which may affect certain species.

Carbon Cycle


Carbon is the fourth most abundant element in the universe and the building block of life on Earth; life on Earth is comprised of carbon-based life forms.

Carbon moves throughout the Earth — between the atmosphere, the oceans, sedimentary rock, soil and plants and animals — in what scientists call the carbon cycle. Carbon cycles through the oceans and the biosphere over both short and long-term time scales. The geological carbon cycletakes place over hundreds of millions of years and involves the cycling of carbon through the various layers of the Earth. The biological/physical carbon cycle occurs over days, weeks, months, and years and involves the absorption, conversion, and respiration of carbon by living organisms. The first step in the biological carbon cycle is the conversion of inorganic atmospheric carbon into a biological form in a process of photosynthesis. In plants and animals carbon dioxide CO2 re-enters the air via respiration.


Understanding how the carbon cycle works is critical to predicting Earth’s climate in the future.

In its pure form carbon exists as diamond or graphite, the lead in pencils. Bound to oxygen, hydrogen and other carbon atoms, carbon forms essential compounds: sugars and fats that provide energy for plants and animals; petroleum, coal and natural gas that power human activity; and carbon dioxide CO2 andmethane CH4, atmospheric gases that trap heat from the sun and warm the Earth. The first step in the biological carbon cycle is the conversion of inorganic atmospheric carbon into a biological form takes place within plants, algae and some bacteria - known as producers – in a process called photosynthesis: light combines with carbon dioxide and water to create carbohydrate molecules known as sucrose (C6H12O6). In oceans, photosynthesis is carried out by microscopic aquatic plants called phytoplankton. In plants and animals - known as consumers - CO2 reenters the air through respiration, as food molecules are broken down for energy and CO2 and other byproducts are emitted.

Animals and plants die and are buried in the earth, but their carbon compounds remain intact, a source of energy for microbes that feast on their remains and produce carbon dioxide CO2 and methane CH4, some of which remains in the soil, some of which is released into the atmosphere. Sometimes, plant and animal remains are buried in the earth or sink to the ocean floor and are protected from microbes. Over hundreds of millions of years animal remains are compressed deeper and deeper into the earth. Tissue and bone are destroyed but the carbon still remains, having formed compounds called hydrocarbons, long chains of carbon atoms bound to each other and to hydrogen atoms. Hydrocarbons are the main component of coal and petroleum — fossil fuels. Humans use fossil fuels to produce heat and electricity, and in doing so the hydrocarbons in fossil fuels are converted into CO2 and released into the atmosphere. Atmospheric carbon dissolves into the oceans or is taken up by plants and the cycle continues. Rock in the Earth’s crust is composed of carbon, formed over millions of years when carbon binds to minerals. Carbon dioxide dissolved in the ocean forms bicarbonate, which combines with calcium to form limestone. Weathering and erosion wash carbon compounds from rock in the Earth’s crust into the ocean. Carbon is also pulled beneath Earth’s crust — a process called subduction — and volcanoes, hot springs and geysers spew carbon dioxide and methane back into the atmosphere. Carbon stored beneath the ocean floor is removed from the biological carbon cycle, entering the geological carbon cycle.

Date: 2015-12-24; view: 2006

<== previous page | next page ==>
The Transformation of Energy | GLOBAL CARBON BUDGET
doclecture.net - lectures - 2014-2024 year. Copyright infringement or personal data (0.007 sec.)