October 14, 2009
Bio 1B – Section 125
Simulated Factors in Predator / Prey Population Growth in Three Cases:
Camouflage-Dependent Dominance, Predation Probability Based Reproduction,
and Predator – Prey Interdependence
To test our own hypotheses of camouflage favored dominance and predator-prey
dependence, we performed three experiments designed to take into account camouflage,
vulnerability to predation, and cycles of both prey and predators.
Our data shows the
most camouflaged prey increased most in population size while the most conspicuous
The data also shows that in the experiment where reproduction depends on
vulnerability, the more conspicuous and better camouflaged preys switched dominance
after 5 generations.
Lastly, a decrease in prey as predators increase and an increase in
prey as the predators decrease in population size.
For the most part our hypotheses were
Because some prey are more visibly available, they tend to be found and eaten
faster by predators, causing the decrease in population of more conspicuous prey.
because it is unlikely all populations increase at the same rate, the second and third parts
of the experiment reflected a more realistic sense of reproduction, where preys don’t
exhibit identical rates of reproduction and where predators do not just multiply, but
depend on prey consumption enabling or disabling its population growth.
The members and gene pool of a population is variable depending on the habitat
that the population is located at and the predators there. Natural selection breeds for
members of the population who can more easily escape predators and survive to the next
breeding season. Thus, the members that survive will be able to pass on their genes and
the specific traits that allow those members to survive will be multiplied through their
offspring. The members that do not have the traits that will allow greater survival will be
eliminated from the gene pool much quicker and as a result, there will be a smaller
percentage of the resultant population with those traits. It was found that when the habitat
and season during which the sticklebacks lived had certain predators, a greater percentage
of that population would have the specific traits that allow them to survive better
(Reimchen, Nosil 2002).
Population sizes also vary, usually in a cyclical format. There are many possible
theories which account for these cyclical fluctuations with the size of the population,
some of which are quantity and quality of foodstuff, predator population size, and
population interaction. In studies that focus on the relationship between the population
and the predators, there has been a slight lag time of the relative size of the population
with the predators compared with the prey. For instance, in one of the studies compiled