BIO 117 Exam 3 Population Ecology - ANSWER Study of how and why population size changes over time, and the effects that population change has on the population. (How new populations get started.) Population Ecology- Change - ANSWER Populations may get larger or smaller without genetic change, and genetic change may occur without population size changes.Population Ecology- Why Study - ANSWER Knowing how populations of food plants grow allows us to plan farms more efficiently. Also knowing how local insect populations grow and decline helps us maintain local ecosystems.Population Ecology - Methods - ANSWER -First ask, how many individuals there are. And is the population declining or increasing?
- Central question answered by monitoring changes of elements such as numbers,
ages, sex ratios over time. 1 / 4
Population Ecology- Caribou on St.Matthew Island - ANSWER -Reindeer introduced to St. Matthew Island in Alaska.-Increased from initial population of 29 to max of 6000 and finally crashed at 44.-Many food sources went dry and with the extreme snow of that year 40000 reindeer died. (Lichens also eliminated) -Nearly 50 reindeer per square mile Caribou (Reindeer)- St. Paul Island - ANSWER -1910 8 caribou introduced population went up to 2000 then when back down and eventually became extinct in 1950.
- Spike caused by lack of predators, less competition for food with other species,
- Had less predators/humans hunting, and better food sources so they could live
better shelter. Crashed because it reached carrying capacity, or disease, or humans hunting the, etc..Caribou (Reindeer)-St. George Island - ANSWER -1915 8 Caribou, population increased then declined and leveled out still live there today.
Exponential Growth/Geometric Growth - ANSWER Claims a population grows (divides by 2) every 24 hours. 2 / 4
E.G Day 1 --> 1 Day 2 -->2 Day 3-->4 Day 4-->8 Day 5-->16 Exponential Growth- Assumptions - ANSWER -Unlimited environment
- Unlimited Resources
- Unlimited space
- After ~34 days, a little over a month the population would exceed 7 billion, the
- Probability of dying is d
- (r)= b-d
Exponential Growth- Paper Folding Analogy - ANSWER - Folding a paper in half increases thickness by x2 every time, just like exponential growth.
current population of the world.Exponential Growth- Mathematics - ANSWER -Probability of giving birth/ dividing is b
-Rate of growth per individual is b-d, also known as r.
-Population size is N, then rate of population growth is r*N 3 / 4
Exponential Growth Equation - ANSWER (dN/dT) = rN
- Means the change in population size per change in time (rate of growth) equals
the rate of the population growth for the individual multiplied by the number of individuals in the population.-When the per capita rate of increase (r) , takes the same positive value regardless of population size you have EXPONENTIAL GROWTH.Exponential Growth- Notes - ANSWER - A populations per capita growth rate stays the same regardless of population size, making the population grow faster as it gets larger. Variable r -Populations limited by resources, cannot grow exponentially all the time -r is r max, it does not change.Logistic Growth- Per capita rate of increase (r) - ANSWER - When the per captia rate of increase (r), decreases as the population increases toward a maximum limit, then we get logistic growth.Logistic Growth/Sigmoid Growth - ANSWER -S shaped growth
- 3 phases: Initial exponential growth, decelerating growth, and fluctuation
around K (carrying capacity) of the environment.
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