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• Nitrogen Cycle

1) The reservoir is the atmosphere and N2 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• Carbon Cycle

1) The reservoir is organic matter and fossil fuels

2) The exchange pool is the atmosphere

3) Photosynthesis from producers removes CO2 from the atmosphere

4) Cellular respiration from consumers & producers returns CO2 to the atmosphere

• Human Activities– Increase of CO2 in the

atmosphere from burning fossil fuels causes global warming.

Global Warming