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Ecology Lec 9 (population distribution and abundance) summary.docx

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Western University
Biology 2483A
Hugh Henry

Ecology Lec 9- Population distribution & abundance Interactions within pop’n- sexual repro & competition Distribution- geographic area where individuals of a species occur Abundance- # of individuals in a given area (size or density) Area occupied is not known- area is bordered based on knowledge of species Abundance can change over time & space - some can disperse (whales), some can’t (plants) - some species hard to determine what an individual is (aspen) - Budding- clones bud off - Apomixis- unfertilized seed/egg can hatch (dandelions, lizards) - Horizontal spread- runners in soil (strawberry) Genet- single genetic individual (product of single fertilization) Ramet- each member of a genet that is independent physiologically Distribution & abundance limited by: 1. Habitat suitability - Abiotic features- moisture, temp, pH, sunlight, nutrients - some species can tolerate wide ranges, some narrow - Biotic features- herbivores, predators, competitors, parasites, pathogens - In Aus., intro cactus pest species spread like crazy, moth released to eat it - Abiotic & biotic interact to determine distribution & abundance - eg. Range of temp is big, but can’t live everywhere because of competitors - Disturbance- events that kill/damage some individuals (some species thrive after the fire e.g) 2. Historical factors - Evolutionary history & geologic events effect modern distribution - Polar bears evolved in arctic, not found in Antarctic because cant disperse though tropical - Continental drift explains distribution of some species - different species even in close together locations, similar species in far away areas 3. Dispersal - Dispersal limitation- prevent species from reaching suitable habitat - Hawain Islands- only 1 native mammal- hoary bat- only one able to fly there - Plants- seeds can’t get too far - Dispersal can be affected by population density - Aphids produce winged forms when density gets high- so they can disperse - Heavy rain connects ponds- fish migrate to nearby ponds (for less competition) Geographic range- entire geo
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