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Lecture 4

BIOL 1001 Lecture Notes - Lecture 4: Natural Selection, The Final Experiment, Phenotype


Department
Biology
Course Code
BIOL 1001
Professor
Roberto Quinlan
Lecture
4

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Effect of Predation on selected Beetles
INTRODUCTION
Population of individual organisms surviving in an environment is under considerable
influence of natural selection. Natural selection is a process in which, traits that are inheritable in
an organism become less or more prominent in a certain population in the habitat. The changes

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that are passed to the offspring tend to have significant effects on the survival of the organism in
future (Arce, Murguia and Frisbie 1987). There is a close relationship between the natural
selection and the alleles. As far as genetics is concerned, an allele is a variant gene and may
result in different phenotypic effects that are observable such as pigmentation. Alleles are
inheritable and thus contribute to the adoption of the organisms in various environmental
conditions.
Predation refers to the association of organisms in the environment whereby one animal
depends on the other for food. Predation is a critical factor in the existence of a population. The
results of predation are two-fold whereby, the population can increase or decrease over a given
time duration. If one of the species is reduced to small numbers, then there will detrimental
effects in the habits. The other species, predator, may also die or migrate from the region in
search of food (Barton and Keightley 2000). On the other hand, if the species preyed increases,
the chances of the predator growth are more likely to happen.
The experiments were carried out to analyze the beetle survival under predation situations
and will indicate significant population trends, and the population is likely to increase. The
experiments consisted of three beetles of different colors. The beetles were colored red, orange
and yellow. The experiment was done through 20 generations each in four trials. The first
experiment had 10 yellow, 10 red, and 10 orange beetles and the predation was established at a
ratio of 3:3:3. The second test contained 40 yellow, 40 red, and 40 orange. The predation ratio
was maintained at a constant ratio. The final experiment was conducted with a population
distribution as the second experiment, but the predation ratio was altered to 3:2:1 in respect to
red, orange, and yellow beetles.

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The three experiments will deliver different results. In the first experiment, it is likely that
one of the colored beetles will get favor meaning the other two will decrease over the 20-
generation period. Similar results are expected from experiment two. In the last experiment, two
colored beetles will perish while the other one will survive (Barton and Keightley 2000). Hardy-
Weinberg equilibrium comes into effect if the beetles’ population remains constant over the
twenty-generation period.
RESULTS
The trend of the beetle population in the experiment was noticeable. In trial one, a
population of 30 beetles with a predation ratio of 3:3:3 was used, and the numbers of the
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