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)
2)
3)
•
The reservoir is the atmosphere
and N2 gas must be converted to a
form usable by producers.
Nitrogen-fixing bacteria convert
nitrogen gas to ammonium which
producers can use
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)
2)
3)
4)
•
The reservoir is organic matter
and fossil fuels
The exchange pool is the
atmosphere
Photosynthesis from producers
removes CO2 from the
atmosphere
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