In my opinion, the definition of fitness can vary greatly, as it depends on what you are talking about, (so I view it as being relative). In humans, being fit means that you are muscular and your body is in good shape. However, this is not true for all organisms. In terms of evolution, I believe being fit means that a population works well with its environment. It doesn't have to be the strongest or the fastest, but instead be what will keep them alive and be able to reproduce and pass on their genes to their offspring. Looking at the reproduction rate of a population is a good way to measure fitness. If a population is able to produce offspring, when there are others who can’t, there is a good chance that they have a high level of fitness.
An example of fitness can be found within the Mexican Blind Fish, (Astyanax mexicanus). These fish have evolved to have no eyes over the years. The caves that they live in do not have a lot of food, so they have to really conserve their energy between meals. Using one's eyes takes up a lot of energy, so by evolving to have no eyes, these fish became better fitted to their environment. These fish really didn't even need their eyes anyways, as they could not see in a dark cave, (Owen).
As one can see, natural selection definitely favored the individuals with reduced visual capacity, as it is a way to conserve energy when it is limited.
The steps I would take to quantify fitness in Astyanax mexicanus are down below. I had a hard time coming up with anything more than this. It will be interesting to see if others have more or less steps!
Steps to see if an organism is “fit”:
1. See if the gene is actually beneficial towards the organism
Is it thriving with this gene?
Are others without this gene failing?
2. Check to see the gene can pass on to offspring
3. Observe offspring to see if trait is still useful
I would also like to add that just because an organism is “fit”, doesn’t mean it will be deemed “fit” for life. An organism’s environment has the possibility to change quickly. For example, if the cave the Mexican Blind Fish were inhabitating suddenly had access to the sun, having no eyes would be a disadvantage instead of an advantage, as they could be easily seen by any predators they might have.
Resources:
Owen, James. “How This Cave-Dwelling Fish Lost Its Eyes to Evolution.” Animals, National Geographic, 3 May 2021, ....www.nationalgeographic.com/animals/article/150911-blind-cavefish-animals-science-vision-evolution.
Hey Emmary,
ReplyDeleteFirst off, I love your background/theme! I'm a big book nerd.
I think you nailed your definition of fitness - I like how you pointed out that the most fit individual doesn't have to be the fastest or strongest etc., but rather the individual able to reproduce and pass on advantageous traits to offspring. Secondly, in relation to the Mexican blind cave fish, I hadn't considered that losing eyes would be considered a form of energy conservation. Previously, I had only really thought the lack of eyes to be a result of the lacking sunlight in their environment - so I learned something new!
Lastly, your steps to measure fitness seem well thought out to me. I would have you consider, however, what actual measurements you might take to collect data. For example, would you count the offspring of parents who have a specific trait? Maybe measure frequency of one trait across a whole population? Just some thoughts :)
Thanks for sharing!
Caroline, thanks for the comment! I like your ideas of what to add to the steps of seeing if an organism is fit or not. I definitely agree with what you are saying about only counting the offspring of parents with a specific trait! By looking at one trait, it would help us to determine which trait is more "fit".
DeleteEmmary! I love that you included the steps to consider if an organism is fit. I think it was also great that you added the reminder that "Once fit doesn't mean forever fit."
ReplyDeleteI liked your example of the fish and how you included a visual as well. Your definition of fitness differed slightly from mine, but I still agree with what you said. I definitely agree with the physical steps you wrote out, and loved how clear you made this entire post.
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