Ch 23: Global Ecology

Ecology Terms Ecology - the study of the interactions of organisms with one another and with the physical environment Biosphere – region where organisms are found from the atmosphere to the oceans Populations – all members of a species within a particular area Community – interacting populations within a particular area Ecosystem – biotic community combined with the abiotic environment Habitat – an organism’s place of residence Niche – an organism’s role in the community

Biotic Community Autotrophs (producers) – use inorganic nutrients & outside energy source to produce organic nutrients. Heterotrophs (consumers) – need a source of organic nutrients –Herbivores – graze on producers –Carnivores – eat only other animals –Omnivores – feed on both plants and animals –Scavengers – clean up on the dead carcasses of larger animals –Detritivores – feed on litter, debris, and dung –Decomposers – complete breakdown of organic matter into inorganic nutrients

Aquatic Ecosystems Marine: seashores, oceans, coral reefs, & estuaries Freshwater: lakes, ponds, rivers, & streams

Terrestrial Ecosystems Forests - dominated by trees –Tropical rain forest –Coniferous forests (taiga) –Temperate deciduous forests Grasslands - dominated by grasses –Tropical grasslands (Savannah) –Temperate grasslands (prairie) Deserts - determined by lack of available moisture –Tundra –Deserts

Figure 26.13

Energy Flow & Chemical Cycling Nutrients cycle through an ecosystem Energy eventually changes form and dissipates through heat Thus, we need constant supply of solar energy

Energy Flow can be described as: Food web – describes who eats whom Food chain – shows a single path of energy flow –Grazing food chain: Leaves  Caterpillars  Tree birds  Hawks –Detrital food chain: Detritus  Earthworms  Shrews Ecological pyramids – shows the flow of energy with losses between each trophic level –Trophic levels - all the organisms that feed on that particular level

Biochemical Cycling Biogeochemical cycle - pathway by which chemicals circulate through ecosystems and involve both biotic & geological components. Reservoirs – fossil fuels, sediments, and rocks, that contain inorganic nutrients available only on a limited basis to living things Exchange pools – atmosphere, soil, and water which are ready sources of inorganic nutrients for living things

Water Cycle Water cycle: 1)Fresh water evaporates from bodies of water 2)Water falls on land and enters the ground, surface waters, or aquifers 3)Water eventually returns to the oceans Human Activities: –Ground water mining – when humans withdrawal water from aquifers that exceed possibility of recharge. –Pollution of our fresh water

Phosphorus Cycle Phosphate Cycle 1)Phosphate is a limited resource located in rocks (reservoirs) 2)Weathering (i.e. rain) wash away phosphate to make it available to producers 3)Consumer eat producers 4)Decomposition of organisms makes phosphate available to producers again Human Activities –Cultural eutrophication – over enrichment of phosphate due to wastes from livestock, fertilizers, & sewage; this can lead to algal bloom and when the algae die off, the enlarged decomposer population uses up all the available Oxygen, which results in massive fish kill

Nitrogen Cycle 1)The reservoir is the atmosphere and N 2 gas must be converted to a form usable by producers. 2)Nitrogen-fixing bacteria convert nitrogen gas to ammonium which producers can use 3)Organisms eat plants and then decompose putting the Nitrogen back into the soil. Human Activities –Fertilizer use results in the release of nitrous oxide, a greenhouse gas that depletes the ozone shield resulting in global warming

Carbon Cycle 1)The reservoir is organic matter and fossil fuels 2)The exchange pool is the atmosphere 3)Photosynthesis from producers removes CO 2 from the atmosphere 4)Cellular respiration from consumers & producers returns CO 2 to the atmosphere Human Activities –Increase of CO 2 in the atmosphere from burning fossil fuels causes global warming.

Global Warming