Predatory On The Beetles Population Biology Essay


Different organisms vary in their inheritable characteristics from each other. Evolution is defined as the change of inheritable traits of an organism in a population over a long period of time when under selective pressure. According to this theory of evolution, the process of natural selection preserves the organisms which have the desirable characteristics in regard to a given environment while eliminating those that have unfavorable characteristics (Corsi, 2005).The organisms which survive increase their fitness and then pass them in form of genes to the next generation of their species. Therefore, generation after generation, these species increase and their well being and become well adopted to their environment. Thus, variation in the genetics of various species leads to evolution. Several factors lead to genetic variations and among these includes mutation. This involves the in the sequence of the DNA of an organism either due to the effects of radiation or chemical substances (Buller, 2005).

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Differences in the characteristic's phenotype can be as a result of different alleles, environmental influences or both these two. If a characteristic is genetic in nature, then any process which selects against or for this trait can lead to the alteration of its genetic characteristics. There exist various selection pressures. These include competition for territories, predation, and others within the natural set up. Population size also affects the degree of genetic variation within an organism. In small populations, there is a higher likelihood for chance incidents to occur where more than one allele are passed onto the next generation (Corsi, 2005).

In the following experiment, there will be examination of the impact of the size of population and predation preference on a given beetle population. The following assumptions will be made during the experiment, the beetle population is completely isolated, there is no emigration or immigration, and mutations do not occur. It is also assumed that all individuals reproduce well and mating occurs. Also, that the only known cause of death is predation. Also, the rate of death is equal to the rate of birth; therefore the population size does not change.

Experimental procedure

The software developed by Newbyte Educational Software was used for this experiment

The program was started by selecting the icon in the program menu under Newbyte/Beetles2. Then the screen with orange leaves was clicked on and then clicked ok on the public information. Then the student typed his/her name that was used to import the data. The beetle population was set at 30 and the initial numbers set at 10 red, 10 yellow and 10 orange. This was at the bottom left of the screen. Then the predation ratio was set at 3:3:3. Based on the knowledge of the situation, the student hypothesized what will occur to the population of each color phenotype over the next 20 generations. Then generation 1 was clicked on and the removal of the parent and offspring beetles viewed as the predator consumes them as the set of the predatory ratio. Generation 1 was clicked on and the remaining offspring moved to the parent group hence more offspring created thus the predator consumes more beetles. Then following the above procedure, the experiment was done until generation 20 was reached. Care was taken to ensure that only 1 generation was clicked on after the events of one generation were completed. Failing to do so would have led to the crashing of the program hence starting over again. At the end of the 20 generations, the option of "cancel" on the "Help wizard" was clicked on and examination of the graph carried out. Then the data was exported and saved.


After conducting the experiment and using the data collected, the predatory effect on the population of beetles can be illustrated in each phenotype for several generations, specifically 20generations.The experiment was done and data collected involving 20 generations of beetle, of varying phenotype, which include yellow, red and orange. Part of the exercise involves use of same ratio of phenotype, from the three different colors available from for beetles. In the portion of the experiment, the ratio is not similar, this is utilized to clearly elaborate and show more details on the impact of predation on a population of certain organisms.

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Figure 1,illustrates the number of survivors for the phenotypes color of beetles in the 20 generations.

As seen from the values given by fixed ratio in the experiment, the population of one colour, yellow, in this case increases dramatically, while the population of orange beetles shows a decrease in size which is observable after a period of several generations, the final red phenotype beetles are seen to reduce consistently from the first trial and later become extinct and the existence is no more

From the data collected is clearly observed that the second part of experiment shows similarities in that in both cases the red beetle's population is seen to decrease while the surviving orange beetle's population increases in the third trial. When it approached a quarter of the generation en about 70 beetles there was little variation on the number, while minor fluctuation were observed all through to the 20th generation.

The population of yellow beetles surviving from all the four trials was shown to be constant with little variation across through the 20th generation as shown in the data collected. Such data has shown that although the population of red beetles and orange beetles decreases to the point of extinct, the yellow beetles have survived all along (Dobzhansky, 1973).


The software developed by new byte educational software termed as new byte/beetles, was used to conduct an experiment to show the impact of prediction of varying phenotypic population of beetles. Based o data collected and the results obtained it is shown that different phenotype of beetles population are affected by predation (Nel, 1973). If the ratios of the red, yellow and orange phenotypes of the beetles are constant it is shown that the red beetles population was often reducing while the orange and yellow beetles changes periodically. Different characteristics are believed to be due to genetic variations this means that different phenotypes or physical characteristics are expressed due to difference in the genetic makeup or genotype of the organism (Dobzhansky, 1973).

Favorable traits acquired by organisms enable them to survive and pass on their gene to the offspring which facilitate survival of the species. From this experiment it is possible to conclude that the red colored beetles were unable to camouflage properly with environment due to their color. They therefore have the lowest chance of surviving elimination from the predators. From the data collected, orange beetles were shown to have a higher probability of survival among the red and orange beetles while yellow beetle had increased chance of surviving elimination from the predators as shown in their population in all the experiment conducted.

A conclusion can therefore be drawn that organism with desirable and favorable trait for a specific environment are able to survive and later reproduce. A change in the predation diet in the second experiment indicates a different trend. The predation ratio for yellow beetle, orange beetles and red beetles changes to 1:2:3.I the other exercise the population of yellow and orange beetles was greater than the red beetle population because the predation ratio diet was higher for red beetles therefore they were at higher risk of being eliminated or eaten by predators. The ratio of predation for orange and yellow beetles is 1:2 respectively as shown by the collected data that suggest the higher chance of survival in the yellow beetles.

In comparison the red beetles had the lowest survival rate followed by orange and finally yellow. Bright coloration makes an insect a highly conspicuous prey to potential predators (Corsi, 2005). Charles Darwin explained that bright colors or advanced morphologies could evolve due to sexual selection. He proposed that bright colors could promote the unpalatability of the beetles to experienced predators. Indeed, prey not edible to predators, are expected to gain by exhibiting recognizable colors; experienced predators can then identify and then avoid attacking such prey.


The physical differences also called the phenotype differences among members of the same species such as the beetle's red, orange and yellow color are brought about by the introduction of new genes (Kim, 1993).These genes are responsible for the modification of the organism's genome and result in the phenotypic differences between the organisms of the same species. With reference to the theory of evolution entire populations, not only individual organism can change over many generations. The theory explains that change in inherited traits and individuals' genes is caused by change among individual organisms.

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Change in the whole population, results from differences in the frequency or the rate of inherited traits within the population varying from one generation to another. Charles Darwin discovered that such variation among the populations leads to the establishment of new species (Nel, 1973).

The change is observed when the individual organism's, or in our case the beetle's traits are passed down from an earlier generation to a later generation. If some traits are passed on more often than others, then the total population will modify over time to reveal the more common traits. This disparity in the reproductive chances of inheritable traits is termed differential reproduction. According to this hypothesis of evolution, the process of expected selection conserves the organisms which have the pleasing characteristics in view of a given environment while eliminating those that have adverse characteristics (Buller, 2005).