Essay on Experiments of the Natural Selection Scenario

Essay on Experiments of the Natural Selection Scenario

Natural Selection
A. Natural selection scenario essay:
The definition of natural selection is the process by which traits become more or less common in a population, because of the effects upon the survival or reproduction. In this situation, a species of plant on the island inhabited by seed-eating finches has seeds that are hard, spiny, and are on average 5mm in diameter. Although the diameter of the seed was about 5mm, there were also appearing some shorter offspring, we could assume that some genetic alteration has occurred (mutation). After the reproduction of some generation, the different inheritable genes associated with the longer seed were broadly distributed in the population (genetic variation). The longer seeds were hardly eaten by finch. So the survival of longer seeds was larger then that of smaller ones. The larger seed could produce more seeds than the smaller one, which meant that the plants producing large seed had more opportunity to live on. (Differential reproductive success). With the change of population phenotype proportion of the two kinds of seed, the allele frequency also changes. That could help us understand the phenomenon by “fitness”. In this situation, because of many shorter seed being eaten, the population of smaller seeds would get smaller and smaller. In contrast, the longer seed were left. In the offspring generation, the larger seed individual genotype would represent the larger amount. That means that fitness of the larger seed was large seed gene amount the largest gene amount is equal to 1, while that of the small seed one was 0 in the end. This kind of change in gene amount was corresponded to the natural adaption of the species in an evolutionary view.

B. Natural Selection Simulation
1. Method
We used normal green paper chips to represent the normal green seed including homozygous G and heterozygous g, the dominate phenotype is green shell corresponding to the genotype of GG and Gg, and used small round brown paper to present the brown tiny gg, and a large picture of the Flower Meadow was set on the table as the real environment. After that we scattered 100 papers on the coneflower field, (25 brown small homozygous, 50 green normal heterozygous and 25 green normal homozygous). Each person took a turn playing the role of predators for each generation. The predator would change, when we did new generation. We did this three times. Predators randomly picked up 50 papers from environment (Flower Meadow). The predator tried to forget the prey, and they picked the first one they saw, because they were hungry and they could find the most obvious one among them. When 50 individuals had been picked up, our group counted the survivors phenotype and genotype, and then use the formula P*2+2PQ+Q*2=1 to predict the allele frequency in the next generation. This whole process repeated three times in our experiment.

2. Results
Our group simulation data:
Lab Section003 simulation data
According to the graph, the initial frequencies of both the dominant allele and recessive were 0.5, and this frequency was fixed. After the first predation, the majority eaten were green one, so among the survivors, the brown allele was more common than green allele. Then, under H-W principle, the next generation offspring of the survivors followed the equation: P*2+2PQ+Q*2=1, the next generation, the allele frequency was on longer the half, instead, the recessive one (g: 0.67 class data) frequency was higher than the dominant one (G:0.33 class data). As the process repeats, the frequency of the recessive alleles keeps increasing, while the dominant alleles keep decreasing. From the data of class, we could find that. In the final generation, the ending frequency of the recessive was 0.67 and the dominant allele was 0.33 (both form class data). From the data of class, the lines increase or decrease in a smooth and steady manner. Specifically in group data, according to the graph and forms, the fitness value of the three genotypes is GG: 0.96 Gg: 1.00 gg:0.85

3. Analysis
In the experiment were used two phenotypes, the green normal and the brown tiny. Since the colors in this environment were mostly brown, the environment could protect the brown one, the main color of the environment could be the key element in this simulation experiment. For instance, the green seed was easy for predator to find, so far the whole population, the higher the brown type’s proportion, the better likelihood of survival the population had. In the graph, the recessive allele grew to the common allele, and the dominant became the uncommon allele. The fitness value of the three phenotypes were GG: 0.96 Gg: 1.00 gg: 0.85. Therefore the brown tiny phenotypes were what nature selected for, and green normal became what nature selected against.

4. Conclusion
1. In my opinion, the data we collected was not perfect, because the data could give us a trend of each gene. The graph of class can indicate the trend of each allele from shapes and slope. If we had done the process many times, I thought the graph would be clearer and become familiar with class graph, because larger population could resist more of random interference from nature event than smaller population can do
2. From the experiment of population Ⅴ, we could obtain that the natural selections were different under different environment. In the beginning, we had the initial condition with population Ⅴ, but we did get different results under two environment. In my opinion, the color in Privet Hedge was green, so the green seed was hard to find and they survived. In finally, we got different allele frequency.