Lab Report

Natural Selection 

Introduction:

In this lab,  we focus on the various changes that rabbits can go through as the seasons change. Animals’ physical characteristics tend to change in order to adapt to a new environment or based on the circumstances. According to The Humane Society, it is mentioned that rabbits eat “flower and vegetables plants in the spring and in the summer and the bark of fruit and ornamental trees and shrubs in the fall and winter.” (What to Do about Wild Rabbits, n.d.) Summer heat reduces the amount of food rabbits consume and can slow their metabolism This could have a negative affect on their growth and nutrient intake.  In the fall and winter, rabbits tend to eat more to increase not only their energy and yet as well their growth and weight.

In terms of their coat. This could be due to their seasonal changes it  is external environment, which causes their fur to shift from white to brown in the summer and brown to white in the winter. This can be due to their way of protecting themselves from their  prey and seasonal change in order to cope with the environment.

The main objective of this laboratory is to look at the evolution of natural selection by observing different physical and environmental changes in rabbits. We will complete this by modifying the rabbit’s dominant fur color, which will be brown, while the white fur will be recessive, floppy ears will be dominant, and long teeth will be dominant.

Materials/Methods

  1. At the beginning in the right corner will be given multiple options to change the mutation of the organism after the generations and time passes which is affected by the habitat, food, and predators.
  2. As a group, we selected both habitats and different combinations of dominant and recessive genes. We decided to select brown fur, straight ears, and long teeth as the dominant genes.
  3. Change the weather and add predators after 3 generations to see which color gene survives in each weather.
  4. Change the food to tough food after 3 generations to see the effect on long teeth vs short teeth bunnies.
  5. Again, add predators after 3 generations to see how it will affect bunnies with floppy ears vs straight ears.
  6. Limit the amount of food to see how it affects the amount of population growth.
  7. At the end of the experiment analyze the generations depending on the habitat, food and predators.

Results/Data

Limited Food Impact Before
After
Population Growth Over Generations

Summer Seasonal Impact  Pre-predation
Post-predation
Population Growth Over Generations
Trait Expression Over Time

Winter Seasonal Impact Pre-predation
Post-predation
Population Growth Over Generations 
Trait Expression Over Time

Trait Comparison: Long vs. Short Teeth Pre-digestion of tough foods
Post-digestion of tough foods
Population Growth Over Generations 
Trait Expression Over Time

Trait Comparison: Floppy vs. Straight Ears Population Growth Over Generations
Trait Expression Over Time

Trait Comparison with Predation: Floppy vs. Straight Ears Population Growth Over Generations
Trait Expression Over Time

Discussion 

With brown fur, straight ears, and long teeth being the dominant genes, the survival rate of bunnies with these types of genes were examined throughout different conditions. Through natural selection, “the process through which species adapt to their environment” some genes appeared to be more favorable through many generations depending on the conditions applied (National Geographic Society, 2019) . 

When the weather changed and the predators were added after the 3rd generation, more brown furred bunnies survived in the summer, and more white furred bunnies survived in the winter. In the summer, adding wolves in the first generation resulted in the species’ death since the 1st generation started out with white bunnies which can be easily seen. This makes sense as the summer had brown colored ground allowing the brown bunnies to camouflage. In the winter, the white bunnies camouflaged with the snow. As a result, the wolves could not see the bunnies that camouflage to the respective weather. Thus, brown bunnies were more favorable in the summer, white bunnies were more favorable in the winter, so depending on the weather, the respective fur color trait would be seen more in the next set of offspring. These observed results supported our hypothesis. 

Next, after waiting 3 generations to have seen long teeth bunnies, which was the dominant gene, tough food was added. The results observed supported our hypothesis that bunnies with long teeth will be more favorable with tough food. Though this was the dominant gene, there were more bunnies with short teeth since it was regular food. Longer and stronger teeth allowed bunnies to adapt to new food which is harder. Adding tough food to the 1st generation that has no bunnies with long teeth resulted in the death of the whole species since they could not eat the food. As a result, the long teeth traits became more common in the offspring of the next generation due to the advantages of having longer teeth. Further, adding wolves to the environment helps to maintain a balance in the ecosystem, so that the bunnies do not overpopulate. 

Further, when waiting about 3 generations for there to be a good amount of floppy and straight eared bunnies to add wolves to the environment, the amount of floppy eared bunnies began to decrease and the amount of straight eared bunnies increased. This is most likely because the straight eared bunnies are able to hear much better than the floppy eared bunnies, thus capable of avoiding threats. According to an article on Clagary Human, loppy eared (floppy eared) bunnies are not good at turning their ears to “pinpoint” the location of a sound (Calgary Humane, 2015). This article also states health disadvantages of having floppy ears as it does not help to regulate temperature. This further proves that the floppy eared bunnies will be at a disadvantage for hearing wolves sneaking up along with health disadvantages. As a result, more straight eared bunnies survive, and reproduce, thus seeing straight ears becoming more common in the presence of wolves. This disputes the made hypothesis as no conditions were expected to affect this trait.

Furthermore, when limiting the amount of food in the first generation, the population of bunnies got to a max of about over 300 bunnies by the 6th generation; however, more than half way through the 6th generation, the population decreased to about 100 bunnies. The population fluctuated from about 100 bunnies to 300 throughout  the next generations.  This makes sense as a limited amount of food can only support a certain amount of bunnies, whereas an unlimited amount of food can support an infinite amount of bunnies and lead to overpopulation. So, if the population reaches above the threshold, some bunnies will die, returning it back to the max amount of bunnies that the limited food can support. If the food was limited, and rough and exceeded the threshold all bunnies with short teeth probably would die since they can’t eat tough food.

Moreover,  these experiments and results show that in the summer the best chance of survival is brown fur, while it is white in the winter for hiding from predators, long teeth are better for all types of food and any food changes,straight ears put the bunnies at an advantage for listening for predators, adn limiting the food keeps the population at a stable level. Individuals with more advantageous and helpful traits will survive and these traits will be inherited by their offsprings, as the individuals with the more helpful traits will have more reproductive success (Khan Academy, 2016). Only the fittest for the environment will survive.

Conclusion

Natural selection has been, and continues to be, one of the most important forces in shaping evolution.  Certain traits in all species exist because of it and will continue to exist or become extinct due to its advantages or disadvantages. The results of our lab prove this by demonstrating that the survival of a species fluctuates depending on which combination of traits exist.  This lab consisted of many experiments which successfully proved the concept of natural selection. For example, when we placed both brown and white haired bunnies in a dirt field and added in predators, the white bunnies were the ones who got eaten because they were not able to blend in with their environment. As generations went by, there were a lot more brown bunnies than white ones because they were the only ones surviving the wolves.  This is simply one example of many which demonstrates that natural selection does play a role in the development of a species. If a trait becomes undesirable, natural selection will occur and organisms will begin to adapt and change to survive. 

References

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