23-08-2012, 10:21 AM
Food chain
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Ecosystem
An ecosystem consists of the biological community that occurs in some locale, and the physical and chemical factors that make up its non-living or abiotic environment.
The study of ecosystems mainly consists of the study of certain processes that link the living, or biotic, components to the non-living, or abiotic, components.
Energy transformations and biogeochemical cycling are the main processes that comprise the field of ecosystem ecology.
Studies of individuals are concerned mostly about physiology, reproduction, development or behavior, and studies of populations usually focus on the habitat and resource needs of individual species, their group behaviors, population growth, and what limits their abundance or causes extinction.
Studies of communities examine how populations of many species interact with one another, such as predators and their prey, or competitors that share common needs or resources.
In ecosystem ecology we put all of this together and, insofar as we can, we try to understand how the system operates as a whole. This means that, rather than worrying mainly about particular species, we try to focus on major functional aspects of the system.
These functional aspects include such things as the amount of energy that is produced by photosynthesis, how energy or materials flow along the many steps in a food chain, or what controls the rate of decomposition of materials or the rate at which nutrients are recycled in the system.
The Transformation of Energy
The transformations of energy in an ecosystem begin first with the input of energy from the sun.
Energy from the sun is captured by the process of photosynthesis. Carbon dioxide is combined with hydrogen (derived from the splitting of water molecules) to produce carbohydrates (CHO). Energy is stored in the high energy bonds of adenosine triphosphate, or ATP (see lecture on photosynthesis).
The prophet Isaah said "all flesh is grass", earning him the title of first ecologist, because virtually all energy available to organisms originates in plants.
Because it is the first step in the production of energy for living things, it is called primary production.
Herbivores obtain their energy by consuming plants or plant products, carnivores eat herbivores, and detritivores consume the droppings and carcasses of us all.
Food Chain
Food Chain is the sequence of populations of an ecosystem which allows food and energy to go through it in a specified direction.
Those on the lower end of chain become food for the ones who are on upper end.
The one who is at top of the food chain is not consumed by any.
The Producers
Producers are the beginning of a simple food chain. Producers are plants and vegetables.
Plants are at the beginning of every food chain that involves the Sun. All energy comes from the Sun and plants are the ones who make food with that energy. They use the process of photosynthesis. Plants also make loads of other nutrients for other organisms to eat.
There are also photosynthetic protists that start food chains. You might find them floating on the surface of the ocean acting as food for small unicellular animals
Decomposers
Whenever something that was alive dies, the decomposers get it.
Decomposers break down nutrients in the dead "stuff" and return it to the soil.
The producers can then use the nutrients and elements once it's in the soil.
The decomposers complete the system, returning essential molecules to the producers.
However
Energy transfer through the food chain is inefficient.
In many circumstances the principal energy input is not green plants but dead organic matter. These are called detritus food chains.
the organization of biological systems is much more complicated than can be represented by a simple "chain". There are many food links and chains in an ecosystem, and we refer to all of these linkages as a food web.
Food webs can be very complicated, where it appears that "everything is connected to everything else", and it is important to understand what are the most important linkages in any particular food web.
Why there are more herbivores than carnivores
In a food chain, energy is passed from one link to another.
When a herbivore eats, only a fraction of the energy (that it gets from the plant food) becomes new body mass; the rest of the energy is lost as waste or used up by the herbivore to carry out its life processes (e.g., movement, digestion, reproduction).
Therefore, when the herbivore is eaten by a carnivore, it passes only a small amount of total energy (that it has received) to the carnivore.
Of the energy transferred from the herbivore to the carnivore, some energy will be "wasted" or "used up" by the carnivore.
The carnivore then has to eat many herbivores to get enough energy to grow.Because of the large amount of energy that is lost at each link, the amount of energy that is transferred gets lesser and lesser ...