ecosystems chapter 25. ecology the study of the interaction of organism with one another and with...
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TRANSCRIPT
Ecosystems
Chapter 25
Ecology
• The study of the interaction of organism with one another and with their physical environment
• Understanding the relationship of organisms to their homes
• An individual organism belongs to:
• Population – interbreeding group of the same species in the same area
• Community – an interacting group of many species that inhabit an area
• Ecosystem – community of organisms together (biotic) with the non-living parts of the environment (abiotic).
Organism Ecosystem
Obtains energy Obtains energy
Transforms chemicalsTransforms Chem.
Changes over time Changes over time
Responds to change Responds to change
Reproduces
Recycles
• The boundaries of ecosystems run together
• Biosphere – fixed boundaries– Extends over the whole Earth, from 2 miles
below the surface to the end of the atmosphere
• Ecosystems have three kinds of organisms:– Producers– Consumers– Decomposers
• Producers are autotrophs: organisms that capture energy and produce their own organic molecules.
• Consumers and decomposers are heterotrophs: organisms that consume molecules made by other organisms.
Food chain:
Carnivore (insectivore)
Herbivore
Producer
Trophic levels
• Omnivores eat from several levels of the food chain, and from several food chains – Food web
• Saprophytes - bacteria, fungi and plants that consume dead material
• Scavengers – animals that eat carcasses or large pieces of dead plants
Pyramid of Biomass
Pyramid of Biomass
• The only ecological pyramid that is always upright is the pyramid of energy.
• Each level passes on only about 10% of its energy to the next level – the rest is lost as heat. “Ten Percent Law”
Pyramid of Energy
Biogeochemical cycles
• Ecosystems lose energy, but recycle materials.
• Water cycle:– 97% in oceans– Through evaporation and transpiration of plants
water enters the atmosphere– Condenses and falls as rain – more on
continents that oceans– Excess returns to oceans by rivers and streams
Carbon Cycle• Most of the carbon is in the form of
bicarbonate ion (HCO3-)
• Living organisms• Carbon dioxide in the air• Carbonates → sediments → rock • 12% of carbon dioxide → organic molecules• Decomposers return CO2 to the atmosphere• Fossil fuels – coal, oil, natural gas → CO2
• “Greenhouse effect” → global warming
What can we do with excess carbon dioxide?
• Reduce output!
• Hide it in trees
• Bury it
• Fertilize the ocean
Nitrogen cycle• Nitrogen makes up 78 % of the atmosphere,
but this is molecular nitrogen, bound together with a triple bond which most organisms can’t break
• Plants need fixed nitrogen, in the form of ammonia or nitrates
• Lightening (5-10%), and nitrifying bacteria
• Rhizobium sp. in root nodules
• Other bacteria convert it to molecular nitrogen – denitrification.
Human effects on the nitrogen cycle
• Increasing the amount of fixed nitrogen and its movement through ecosystems.
• Greenhouse gases
• Acid soil and acid rain
• Loss of soil fertility
• “dead zones” in oceans
Phosphorus cycle
• DNA, RNA, ATP and cell membranes
• Rare in nature
• Sink to bottoms of lakes and oceans
• Terrestrial ecosystems are good recyclers of phosphorus
• Limiting nutrient for many organisms – excess causes “blooms”