dp biology option c.1 species and communities
Post on 19-Jul-2015
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The distribution of species is affected by limiting factors
• A limiting factor is the factor that is most scarce in relation to an organism’s needs
• Plant distributions are affected by abiotic variables: temperature, water availability, light intensity, soil pH, soil salinity, and availability of mineral nutrients.
• Animal distributions are affected by temperature, water, breeding sites, food supply, and territory.
The distribution of species is affected by limiting factors
• Every plant species has a range of tolerance for each limited factor. Excluded from areas outside their “range.”
• Tropical plants are adapted to limit transpiration and photosynthesis is efficient in hot weather.
• Plants from the far North have anti-freeze like chemicals to protect their cells
Each species plays a unique role within a community because of the unique combination of its spatial habitat and interactions with other species
• Within an ecosystem, each species fulfills a unique role, called its ecological niche.
• Niche includes: habitat, how obtain food, interactions with other species.
• Abiotic variables: Must be within zone of tolerance
Competitive exclusion principle: two species cannot survive indefinitely in the same habitat if their niches are identical
• P. aurelia thrives by itself in ideal laboratory conditions
• P. caudatum thrives by itself in ideal laboratory conditions
• When cultured together, both species are reduced. P. caudatum reduced far more than P. aurelia
Allott 608
Competitive exclusion principle: two species cannot survive indefinitely in the same habitat if their niches are identical• The Yellow-rumped warbler &
Bay-breasted warbler occupy the same niche.
• These species typically forage in different parts of the same tree.
• Avoid competition with each other.
Allott 609
Interactions between species in a community can be classified according to their effect
• Competition: when two species require the same resource, and the amount needed by one reduces the amount available for the other.
• Herbivory: primary consumer feeding on producers.
• Predation: consumer feeding on another consumer.
• Parasitism: one organism feeds off of another, but does not necessarily kill it.
• Mutualism: two organisms live in close association, and both benefit
• Commensalism: one organism benefits, the other is neither helped nor harmed
Keystone species: Community structure can be strongly affected by keystone species
• A keystone species has a disproportionate effect on the structure of an ecological community.
• Robert Paine removed the sea star Pisaster from one area and compared the results where Pisasterwas allowed to stay.
• In the “removed” area – the other members of the food web immediately began to compete with each other.
• Succession of dominant species, some species wiped out, others emigrated.
• Within a year of Pisaster’s removal, species diversity had decreased from 15 to 8 species.
Sources
ContentAllott, 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.
Images
Unless otherwise noted, images are obtained from Pixabay(www.pixabay.com) and used under the CC0 Public Domain license.
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