ECOSYSTEMS vary in size. They can be as small as a puddle or as large as theEarth itself. Any group of living and nonliving things interacting with eachother can be considered as an ecosystem.Within each ecosystem thereare habitats which may alsovary in size. A habitat is theplace where population lives.A population is a group ofliving organisms living in thesame place at the same time.All of the populations interactand form a community. Thecommunity of living thingsinteracts with the nonlivingworld around it to form theecosystem.
1. Energy Flow – passage of energy through the components of theecosystem > Autotrophs – convert light energy into chemical energy > Heterotrophs – obtain chemical energy from food > Decomposers - feed on all levels2. Chemical Cycling – circular movements of materials within theecosystem > ecosystems are more or less self-contained in terms of materials > chemical components are cycled between abiotic components (air, water, soil) and biotic components of the ecosystem.
This figure withplants, zebra, lionand so forthillustrates the 2main ideas on howecosystem function:ecosystems haveenergy flows andecosystem cyclesmaterials. These 2processes are linkedbut they are notquite the same.
> The transformation ofenergy in an ecosystembegin first with the input ofenergy from the sun. Energyfrom the sun is captures bythe process ofPhotosynthesis. CarbonPhotosynthesisDioxide is combined withHydrogen to producecarbohydrates. Energy isstored in the high energybonds of adenosinetriphosphate or ATP.
Diversity >the varierty of different organisms in a community is its biodiversity. Two components: species richness (how many ?) relative abundance of species >ecologists consider both richness and relative abundance in measuring biodiversity. Prevalent form of vegetation >applies mainly to terrestrial situations >determine to a large part what other organisms will live there Response to disturbance >some communities are stable (e.g. cedar and hemlock forests may last 1000’s years); when disturbed, such communities rebound to original state very slowly. >other communities are constantly changing and unless disturbed by fire, for example, succession would lead to different species composition (e.g. grasslands require periodicfires to remove competitors and allow grasses to dominate). Therefore disturbance plays a vital role in determining community structure and composition. Trophic structure >feeding relationships among various species making up a community. >determines pasage of energy and nutrients from plants and other primary producers to herbivores to carnivores.
Competition may occur when a shared resource islimited Predation leads to diverse adaptations in predatorsand prey Predation can maintain stability in a community Symbiotic relationships help structure communities. Disturbance is a dominant feature of mostcommunities