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BIOL 215 Study Guide - Quiz Guide: Nostoc, Cladophora, Epiphyte

Course Code
BIOL 215
Neil Price
Study Guide

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2) a) r = (ln Ro)/G (Ro is the net reproductive rate over the specified period and G
is the period in days)
(ln 15)/ 5.5 = approx. 0.49 indiv/(indiv * days)
b) dN/dtN = r * (K N)/K (dN/dtN is the realized per capita rate of increase, K is
the carrying capacity and N is the current population density)
0.49 * (1.2 * 10^6 0.9 * 10^6)/(1.2 * 10^6) = 0.12
c) dN/dt = N * r * (K N)/K (dN/dt is the instantaneous rate of change of the
population, r is the intrinsic rate of increase per capita, K is the carrying capacity
and N is the current population density)
0.49 * 0.6 * 10^6 * [(1.2 * 10^6 0.6 * 10^6)/ 1.2 * 10^6] = 14.700 cells/day
3) When there is no predator present, the prey population oscillates drastically over
the carrying capacity of 100 individuals, going anywhere from approximately 130
to 15 individuals over the course of one generation, and then booming again. The
presence of the predator keeps the prey population more steady, with less dramatic
variance; predation keeps the population from growing too much, to the point
where they`ll exhaust their environment`s resources (as herbivores, they`d
overconsume the plants) and as a consequence starve until the population left is
almost none. Without the predator, the constant population oscillations greatly
decrease genetic variability among the prey (with constant rise of 100+ individual
populations from only a few initial individuals, there will be a fair amount of
inbreeding and not a very wide gene pool), therefore the predator not only keeps
the increase/decrease cycles in prey density to a more reasonable level, they also
keep the genetic pool more diverse.
4) The sediment represents refuge for the prey from the action of the predator and
the additions represent the immigration of new individuals to the population. A
scenario where prey isn`t able to hide from predators will inevitably lead to the
extinction of the prey and the consequent extinction of predators by starvation. The
same result was achieved after altering considerably the initial amounts of
predators and prey on Gause`s experiments. After adding the substrate as a refuge
for the prey paramecium, the predators killed all the prey in the free water and then
starved to death, leaving the space open for the paramecium in the substrate to
come out and colonize the environment, creating a predator-free environment.
After regular introduction of new individuals to the system, the populations started
oscillating (a growth in the number of Paramecium followed by a growth in
Didinium, a consequent decrease of Paramecium followed by a decrease in
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