12_Ecosystem_Ecology (3) - BI SC 002 LECTURE 11ECOSYSTEM...

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BI SC 002 LECTURE 11—ECOSYSTEM ECOLOGY Draft: December 2, 2010 An ecosystem is defined as a collection of all of the organisms in the same place at the same time plus all of the physical aspects of the environment. These physical aspects include energy, nutrients, and climate. In regards to energy, the earth is an “open system”. That means that energy is constantly being added to the earth. Energy is needed for everything in a living organism to function. All of the energy used by organisms on earth comes directly from the sun. Light energy from the sun is transformed into chemical energy through the process of photosynthesis. Plants, algae, and some bacteria use the sunlight to produce carbohydrates, proteins, and fats. Producers are the organisms that capture the energy from the sun. All other organisms are called consumers . Consumers must obtain energy by eating something with energy. A primary consumer , sometimes called an herbivore is an organism that consumes a produce. A secondary consumer , which is a carnivore (meat eating), eats the primary consumer. A tertiary consumer would eat a secondary consumer. All the while, as organisms die or are reduced to fecal matter, decomposers are returning nutrients back to the soil. That pathway of energy (producer primary consumer secondary consumer tertiary consumer) is called a food chain . However, in real life, it is not just a linear path. Animals may be multiple consumers. Humans can eat plants (making them a primary consumer) but also eat meat (making them a secondary or tertiary consumer). All of the food chains in an ecosystem (all of the ways organisms interact through consumption) make up the food web . At each level in a food chain or food web, some energy is lost. Some energy is used by the organism to be able to function, but much is lost as heat. The primary productivity of an ecosystem is the total amount of light energy converted to chemical energy per unit time. The net primary productivity is the primary productivity minus the amount of energy expended by plants to fuel their metabolic activity. This is basically the amount of energy available to
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12_Ecosystem_Ecology (3) - BI SC 002 LECTURE 11ECOSYSTEM...

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