Evolution Dot Lab: Phenotype Shifts and Natural Selection

Categories: Biology


In the Evolution Dot Lab, we conducted experiments to assess the frequencies of recessive and dominant alleles in various environments and examined the impact of the environment on color phenotypes. Our findings revealed that in the black environment, the red color phenotype had the highest frequency at 46%, while both the black and white color phenotypes exhibited an equal frequency of 27%.

In the red environment, conducted under darkness, we observed that the red color phenotype peaked at 60% during generation 4 but eventually decreased to 0% by generation 5.

Additionally, the white color phenotype exhibited the second-highest frequency, reaching 40% during generation 4, while the black color phenotype decreased to 0% by generation 4.

In the white environment, we found that the red color phenotype dominated with the highest frequency of 42%, attributed to its rapid reproduction rate. The white color phenotype followed with a frequency of 31%, and the black color phenotype had an allele frequency of 27%.


Evolution is the fundamental process that has shaped all life on Earth, resulting in the incredible diversity observed in the fossil record and in the world around us.

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At its core, evolution reflects the common ancestry shared by all living organisms. Over successive generations, life has adapted to its changing environment, with genetic variations influencing the observable traits or phenotypes of organisms (Klappenbach, 2017).

Evolution occurs through alterations in allele frequencies within populations over time. While natural selection is a crucial driver of microevolution, other mechanisms, including genetic drift and gene flow, also play significant roles (Understanding Evolution, 2020). On a broader scale, macroevolution encompasses evolutionary changes that occur above the species level, resulting in the emergence of new groups of organisms, such as mammals or flowering plants, through speciation events (Urry, 2020).

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Mutations, which arise during DNA replication and recombination, represent a source of genetic variation. These permanent alterations in DNA sequence can manifest as substitutions, deletions, or insertions of base pairs (Dr. Sturm, 2019). While many mutations are benign, some can lead to cell death or tumor formation. Organisms have evolved mechanisms to repair damaged DNA, although mutations remain a relatively rare event and are unlikely to cause substantial changes in allele frequencies within a single generation.

Genetic drift, in addition to natural selection, mutation, and migration, stands as one of the foundational mechanisms of evolution. In each generation, some individuals may, by chance, pass on more genes to their descendants than others, influencing the genetic makeup of subsequent generations. These genetic changes occur randomly and can affect a population's evolution, although they do not necessarily produce adaptations.

Gene flow, or migration, involves the movement of individuals and their genetic material (DNA) from one population to another. This process can introduce new gene versions to populations where they previously did not exist, contributing significantly to genetic variation.

Natural selection, along with genetic drift, is one of the primary mechanisms driving evolution. It begins with the presence of variation in traits within a population. Since environments cannot sustain unlimited population growth, not all individuals will successfully reproduce. Over time, individuals with traits that align with the environment's demands will thrive, while those less suited will perish. This process results in the propagation of successful genetic traits within the population.

Sexual selection, a subset of natural selection, influences the survival and reproduction of individuals based on their morphological and behavioral traits. These traits make individuals attractive mates, increasing their chances of reproducing and passing on their desirable characteristics to their offspring. For instance, species with traits such as larger antlers in male deer may have an advantage in mating competitions, ultimately shaping the characteristics of future generations.

The themes of evolution discussed here played a vital role in our laboratory experiment. We observed a decline in a specific population over generations, driven by various factors, including the lower frequency of black dots due to their recessive nature in mating. This influenced the predators' selection of dots, favoring the more common color phenotypes. In our study, the null hypothesis regarding phenotype survival posited that there would be no difference other than what randomness might provide, while the alternative hypothesis suggested that phenotype survival varies depending on the environment. Our rejection of the null hypothesis was based on the notable prevalence of red offspring in the red environment. Regarding genotype, the null hypothesis proposed no difference between dominant and recessive colors beyond random chance, while the alternative hypothesis indicated that colored dot survival depends on the dominant color in the environment. We rejected the null hypothesis in light of the decline of black dots due to the probability of producing black offspring.


Step One: Setup

To conduct the Evolution Dot Lab, we gathered the following materials: 10 black dots, 10 white dots, 10 red dots, black sheets of paper, white sheets of paper, red sheets of paper, a pair of tweezers, a petri dish, and an envelope. Within our group, we designated two roles: a predator and a prey. The predator held tweezers and a petri dish, while the prey arranged the dots randomly on a selected colored paper. Each color paper could only be used once in three trials. For instance, if white paper was chosen for one trial, red and black papers were designated for the subsequent trial. A timer, typically the teacher, initiated the experiment by announcing the start and timing 12 seconds. During this period, the predator randomly picked up dots with their tweezers. When the timer stopped, the prey placed the remaining dots of each color on the colored paper into an envelope. Simultaneously, the predator recorded the number of kills for each color and noted the count of surviving dots for each color.

Step Two: Offspring Determination

Following the completion of step one, the prey blindly selected two dots at a time from the envelope to determine the color of the offspring. If both dots were black, the offspring was black. If both dots were white, the offspring was white. In the case of two red dots, we used a coin flip to determine the offspring's color. If one black dot and one white dot were selected, the offspring was considered red. If the coin landed on heads, the offspring was red; if it landed on tails, we flipped the coin again. A heads result on the second coin toss indicated a black offspring, while tails led to a white offspring. If one black dot and one red dot were chosen, a coin flip decided the offspring's color. Heads meant a black offspring, while tails resulted in a red offspring. Similarly, if one white dot and one red dot were selected, a coin flip determined the offspring's color, with heads indicating white and tails indicating red. We repeated this process until all the dots in the envelope were used up. If one dot remained and could not reproduce, it was returned to the envelope with the breeding dots and offspring.

Step Three: Data Recording

After completing step two, the breeding dots and their new offspring were placed back on the chosen colored sheet of paper. We then tallied the number of dots of each color and recorded these counts on the data spreadsheet for the next generation. Our initial generation consisted of 10 black dots, 10 white dots, and 10 red dots.

Step Four: Repetition

Once step three was finished, we repeated steps one, two, and three until we reached the sixth generation or until there were no dots left to reproduce.

Step Five: Additional Colored Papers

We then repeated steps one, two, three, and four on the remaining colored sheets of paper, following the same procedures as described above.

Step Six: Dark Environment Trial

In our final trial, we completed steps one, two, three, four, and five, but this time, we conducted the experiment in complete darkness, with the lights turned off.


In the black environment, the phenotypic percentages for red and white varied, with black consistently having the smallest percentage across all six generations. While there were small fluctuations in allele frequency, by the end of generation six, both alleles were present at 50%.

When the background was white, both white and black phenotypic percentages remained low, while red percentages consistently ranked the highest throughout all generations. The effect of the white background on allele frequency appeared to be minimal, as the percentages hovered near 50%.

In the red environment, the red and white phenotypes initially increased in the first few generations, while the black phenotype rapidly declined. By the fourth generation, all phenotypes reached zero, and allele frequencies also dwindled towards the end.


The outcomes in the black environment were largely predictable, considering that black represents the dominant allele. As anticipated, regardless of the background, it became evident that allele frequency for the dominant allele (B) would eventually catch up to the recessive allele (b), which indeed occurred.

However, the results in the red background were less predictable. Initially, the recessive allele seemed to dominate, eventually leading to population extinction. This phenomenon could be attributed to the initial demise of the black phenotype, which harbored two dominant alleles. Once the black phenotype disappeared, the extinction of the entire population on a red background became inevitable, as red was challenging to breed successfully.

In the white background, predictions were complicated by the advantage of white dots blending into their environment. Despite being the recessive allele, it appeared more dominant due to the influence of the background, ultimately leading to its higher allele frequency.

The null hypothesis posited that there would be no difference in the survival of colored dots beyond what randomness could provide. However, our results demonstrated significant differences in phenotype survival in response to the environment and genetic allele frequencies, indicating that predictions could be made beyond random chance.

The prominence of the black allele in this experiment can be attributed to the black background, which favored the already dominant allele and promoted the prosperity of the black phenotype.

Population decline in the lab occurred primarily because the black phenotype, which carried the dominant allele, was easily visible on the red background and became prey for the predator. With the extinction of the black phenotype, the subsequent generations followed suit.

The rise of the white allele in allele frequency, despite its recessive nature, was due to the advantageous environment that allowed it to blend in and avoid predation. While recessive, it survived and thrived due to the environmental conditions.

This experiment relates to natural selection, a fundamental mechanism of evolution, alongside mutation, migration, and genetic drift. Natural selection is characterized by the environment favoring certain phenotypes, leading to their survival and reproduction (Understanding Evolution).

COVID-19 can be associated with natural selection as it represents a variation of existing viruses. It emerged as a distinct virus within the coronavirus family through natural processes. It did not come out of nowhere but evolved naturally from preexisting viruses (Myers). COVID-19, being a new strain of coronavirus, developed through natural selection, as viruses with no constraints tend to proliferate. To combat its spread, measures such as staying home, maintaining social distance, practicing frequent handwashing, and covering coughs are recommended by the WHO (World Health Organization) (WHO).

Reference List

  1. Urry, L. A., Cain, M. L., Wasserman, S. A., Minorsky, P. V., & Campbell, N. A. (2020). Campbell Biology in Focus. Hoboken, NJ: Pearson.
  2. Hopkins, John. “What Is Coronavirus?” Johns Hopkins Medicine. Retrieved from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus
  3. “Advice for Public.” World Health Organization. Retrieved from: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/advice-for-public
  4. DNA Mutation and Repair. Retrieved from: www2.csudh.edu/nsturm/CHEMXL153/DNAMutationRepair.htm
  5. Egnor, Michael. “Did COVID-19 Virus Evolve by Natural Selection?” Evolution News, 2 Apr. 2020. Retrieved from: evolutionnews.org/2020/03/did-covid-19-virus-evolve-by-natural-selection/
  6. Klappenbach, Laura. “Evolution: The Basics and Beyond.” ThoughtCo, 19 Dec. 2017. Retrieved from: www.thoughtco.com/introduction-to-evolution-130035
  7. Mechanisms of Microevolution. Retrieved from: evolution.berkeley.edu/evolibrary/article/0_0_0/evo_39
  8. Natural Selection. Retrieved from: evolution.berkeley.edu/evolibrary/article/evo_25
Updated: Jan 23, 2024
Cite this page

Evolution Dot Lab: Phenotype Shifts and Natural Selection. (2024, Jan 23). Retrieved from https://studymoose.com/document/evolution-dot-lab-phenotype-shifts-and-natural-selection

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