Option C.2 Communities & Ecosystems IB Biology

R. Price

v. 1 2015

Allott 613

#1: Most species occupy different trophic levels in multiple food chains

Trophic level• Level = position on food chain• Level can vary -> life cycle, season,

food availability

Determining trophic level• Examine mouth parts/teeth• Examine food in gut• Examine feces

Allott 614

#2: A food web shows all the possible food chains in a community

• Trophic relationships web-like• Many consumers feed on more

than one species

Allott 615

Allott 616

Allott 616

#3: The type of stable ecosystem that will emerge in an area is predictable based on climate

Climate• Temperature: distribution of

organisms, cell respiration & photosynthesis rates, decomposition, transpiration, productivity• Precipitation: photosynthesis &

decomposition rates

Allott 617

Allott 618

Allott 618

Allott 619

Allott 619

Allott 619, 620

Allott 620

Allott 620

#4: The percentage of ingested energy converted to biomass is dependent on the respiration rate

Production• Plants -> organic matter synthesized by

photosynthesis• Animals -> food absorbed after

digestion• Gross production -> total amount of

organic matter produced per unit area per unit time by a trophic level• Net production -> amount of gross

production remaining after subtraction of the amount used for respiration by the trophic level

Net production = gross production - respiration

Allott 622

#5: Disturbance influences the structure and rate of change within ecosystems

• Secondary succession takes place where is has already been an ecosystem• Disturbance – natural or human

caused• Early in succession – high rates of

respiration, productivity, & biomass accumulation. High species diversity• At climax – rates slower,

ecosystem stable, resistant to change

Allott 623

#6: In closed ecosystems energy but not matter is exchanged with the surroundings

• Natural systems -> open. Exchange matter & energy• Artificial systems -> closed. Only

exchange energy• Isolated systems -> theory. No

exchange of matter, energy

Allott 624

Sources

Content Allott, Andrew, and David Mindorff. Biology: Course Companion. 2014 ed. Oxford: Oxford UP, 2014. Print. Oxford IB Diploma Programme.

Walpole, Brenda. Biology for the IB Diploma. 2nd ed. Cambridge: Cambridge UP, 2014. Print.

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