Author: Joanna Xu
Editors: Rachel Chen, Miriam Hiekal
Artist: Emily Hu
If you’ve ever taken an introductory biology class, you’re probably familiar with the role of evolution in survival. Defined as the change in the traits and behavior of groups of organisms over time, evolution affects all aspects of life, from the molecular level to entire species. You may know of Charles Darwin, renowned for his theory of natural selection, or have seen The March of Progress, originally titled The Road to Homo Sapiens, by artist Rudolph Zallinger. The artwork depicts an ape-like figure slowly manifesting into present-day humans over the course of 25 million years. With new cutting-edge technology and teams of researchers worldwide, studying evolution has become much more efficient and interesting, with studies ranging from transparent frogs to pregnant males.
To start, we have glass frogs. As suggested by its name, this frog’s skin is almost entirely clear, allowing viewers a clear view of its internal organs. Typically, a frog's skin color indicates its level of danger; more vibrant colors are associated with higher toxicity. You may have heard of green, yellow, blue, and even red frogs, but clear? That’s unusual. What could be the advantages of having transparent skin? According to researchers, this is yet another form of camouflage, similar to that of polar bears and color-changing geckos. In this case, though, the frog’s transparency allows it to adapt to the color of its environment instantly, making it extremely hard to find in most settings. Further research reveals that this frog species is not the only one with this trait. There are also transparent shrimp, fish, butterflies, and even beetles.
Another intriguing example of evolution is the pregnancy of male seahorses. In most species, eggs and fetuses are usually carried by the female, while their male counterparts are responsible for finding food or, at times, not present at all. However, when it comes to seahorses, as well as the closely related pipefish and sea dragon species, embryos are carried and birthed by males. The female members are in charge of courtship and impregnating the male, though she still produces the eggs. This means that while the male grows the embryos in his body, the female can prepare the next batch of eggs. For seahorses, a species with monogamous relationships, this reversal of roles allows for many more offspring to be produced than in the typical arrangement. This way, these small creatures have a much greater chance of leaving offspring in the world when they die, preventing species extinction.
Lastly, and possibly the most terrifying, is the evolution of New York City rats. In terms of bone structure, research has shown an evolutionary shift towards longer noses as well as shorter upper tooth rows in response to their higher quality, softer diets residing in NYC. Compared to rats still residing in their ancestral regions, New York City rats have different genes associated with metabolism, diet, nervous system, and movement. One gene, CACNA1C, is associated with psychiatric disorders in humans, suggesting higher levels of anxiety in city rats. Additionally, compared to decades ago, these rats seem to have greater resistance to rodenticides, making them harder to eliminate. Through evolution, these rats have adapted to city life–pretty much permanent residents!
Whether rats or frogs, evolution allows species to enhance their chances of survival wherever they are. Whether it is immunity or body organs, nature sure has adapted in many ways. Survival of the fittest as you know it. As research into evolution continues to expand, I’m sure we’ll come to find many more exciting ways evolution has changed the world around us.
Citations:
Barnett, James B et al. “Imperfect transparency and camouflage in glass frogs.” Proceedings of
the National Academy of Sciences of the United States of America vol. 117,23 (2020): 12885-
12890. doi:10.1073/pnas.1919417117
Harpak, Arbel et al. “Genetic Adaptation in New York City Rats.” Genome biology and
evolution vol. 13,1 (2021): evaa247. doi:10.1093/gbe/evaa247
Jones, A G, and J C Avise. “Mating systems and sexual selection in male-pregnant pipefishes
and seahorses: insights from microsatellite-based studies of maternity.” The Journal of
heredity vol. 92,2 (2001): 150-8. doi:10.1093/jhered/92.2.150
Puckett, Emily E et al. “Variation in brown rat cranial shape shows directional selection over
120 years in New York City.” Ecology and evolution vol. 10,11 4739-4748. 15 Apr. 2020,
doi:10.1002/ece3.6228
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