Option C.3 Impacts of Humans on Ecosystems

IB Biology

R. Price

v. 1 2015

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#1: Introduced alien species can escape into local ecosystems and become invasive

• Endemic organism = native. Part of a food web. • Alien = introduced. If survives,

may take over.• Compete with native species. Can’t have

two organisms in same niche• May not have a predator in new location

• Introduction may be accidental, intentional, or a form of biological control

Accidental Introduction: Zebra Mussels

Intentional Introduction: Japanese Knotweed

Pest Control Introduction: PR Cane Toad

#2: Competitive exclusion and the absence of predators can lead to reduction in the numbers of endemic species when alien species become invasive

Competitive Exclusion:• Alien species can be

reproductively successful• May dominate ecosystem• Two species with overlapping

niches cannot continue occupying same niches

http://i-biology.net/

Puerto Rican Cane Toad - Introduced: Queensland, Australia (1935) - Job: Eat Sugar Cane Beetles - Evaluation : DISASTER

Sugar Cane Beetle

.

Scolia ruficornis (Scoliidae) - Introduced: Thailand (1963) - Job: Eat Coconut Rhinocerous Beetle - Evaluation : SUCCESS

http://www.agnet.org/library.php?func=view&id=20110718163847

Coconut Rhinocerous Beetle (accidental introduction: rubber trees import)

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#3: Pollutants become concentrated in the tissues of organisms at higher trophic levels by biomagnification

Bioaccumulation• Some toxins not excreted easily• Some toxins are fat-soluble• These toxins build up in the bodyBiomagnification• Toxins become more concentrated

at each trophic level• Each stage in food chain, consume

large quantities of preyBioaccumulation + Biomagnification

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#4: Macroplastic and microplastic debris has accumulated in marine environments

Macroplastic & microplastic debris is mostly from liter blown into water systems

Consequences:• Degraded plastic releases chemicals into

ocean (bioaccumulate & biomagnify)• Plastic absorbs other chemicals &

concentrates those toxins• Animals eat or become tangled

Enormous “islands” of garbage around the globe called gyres.

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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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