Handout 8

# Handout 8 - BILD 3 Fall 2008 Section Mon 9-9:50 AM HANDOUT...

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BILD 3 Fall 2008 Section: Mon 9-9:50 AM Page 1 HANDOUT 8 - TA I. Ecology workshop Quantitative aspect of ecology o Population growth Intrinsic rate of increase (r): dependent on 4 factors (birth rate, death rate, immigration rate, and emigration rate) r = birth death + immigration emigration But assuming immigration = emigration, then Exponential growth Unlimited resources + unchecked unrealistic Differential equation where N = population size of 1 species Solution to differential equation N t = N 0 e rt where N t = population size at time t, N 0 = initial population size J-shaped curve Doubling time : time it takes for population to double in size (where N t = 2N 0 )

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BILD 3 Fall 2008 Section: Mon 9-9:50 AM Page 2 Logistic growth Takes into account limited amount of resources realistic Growth is checked by a carrying capacity (K) value (the maximum population size the environment can support for an extended period of time) Differential equation S-shaped curve Interaction between 2 species of organisms o Competition coefficients α 12 = effect of species 2 on species 1 α 21 = effect of species 1 on species 2 o 3 main cases 12 = α 21 Both species can coexist but their respective carrying capacity K values will decrease o K 1 : max number of species 1 in absence of 2 (N 1 when N 2 = 0) o K 2 : max number of species 2 in absence of 1 (N 2 when N 1 = 0) o K 1 ’: max number of species 1 in presence of 2 K is a limit (asymptote) that prevents N from passing it N > K population will decrease N < K population will increase N = K population will stay the same
BILD 3 Fall 2008 Section: Mon 9-9:50 AM Page 3 o K 2 ’: max number of species 2 in presence of 1 We know that o K 1 > K 1 ’ and K 2 > K 2 o And the actual relationship is given by the equations 1 = K 1 α 12 N 2 2 = K 2 α 21 N 1 Knowing these equations, we can calculate the number of species 1 (N 1 ) that will drive species 2 to extinction (K 2 = 0) and vice versa By graphing these values, we can find the equilibrium point where both species will coexist and know how many of each species will result at that equilibrium point NOTE : the equilibrium point will have more organisms than if either species existed alone because both species will efficiently use all possible resources that is necessary for their survival 12 = α 21 Both species occupy the same niche and they are equally resourceful but one species will eventually be displaced by the other simply by chance

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BILD 3 Fall 2008 Section: Mon 9-9:50 AM Page 4 12 > 1 or 21 One member of the more resourceful species can drive out 2 members of other species so the less resourceful species will be driven to extinction II. Terms/phrases to know Lecture 22 (11-17-08) o Mitochondrial Eve o Y-chromosome Adam o Coalescence time o HapMap project o Single nucleotide polymorphisms o “Great Leap Forward” Lecture 23 (11-19-08) o Ecology o Biosphere o Biome o Desertification o Ecosystem o Community o Climax community o Primary succession o Secondary succession o Ecological niche o Abiotic
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Handout 8 - BILD 3 Fall 2008 Section Mon 9-9:50 AM HANDOUT...

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