Fitness

 Fitness in Evolution

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If you were to ask me before this class how to define fitness in biology a few thoughts would come to mind. The first thought that I would immediately think of is the phrase “Survival of the fittest” which is something that has been hammered into my brain since my first biology class. Another thought that comes to mind is the meme above that I absolutely love and no matter how many times I see it, it always takes me approximately 2 minutes to stop laughing/giggling. The third thought that would come to mind is a muscular kangaroo squaring up and ready to fight (I credit this thought to the awesome childhood movie, Kangaroo Jack).

Now that I am in an actual evolution class, I think I would define it as ultimately a description of how successful a species is at reproducing. I believe this is a very basic definition of fitness in evolution but really describes the gist of what we discussed in class. It represents sexual and natural selection and concerns specific genotypes/phenotypes that are completely dependent on the environment. A slide in the class described fitness as having an average contribution to a gene pool in future generations that are made by individual organisms of a specific genotype or phenotype. Fitness can be measured by the number of offspring that are produced from the individual organisms that have a certain genotype/phenotype that is then seen in future generations with a certain extent of reproductive success.

A specific example of fitness playing out is comparing brown beetles and green beetles. Brown beetles have a consistently higher survival rate compared to green beetles. Because fitness is a relative concept, the theory is that the color of the beetles is a key factor in the survival and better reproductive success. Brown beetles have an easier time blending in with their surroundings than with green beetles, depending on the environment. According to a study, done to determine the survival rate of the two beetles, 95% of brown beetles survive and reproduce compared to the 33% of green beetles. 

I think I have gotten into the habit of immediately thinking of what humans consider ‘fit’ compared to what the actual definition of evolutionary fitness is. Hopefully, by the end of this class, I will be able to immediately think of the right definition of ‘fitness’ in terms of biology; though one of the thoughts that will always come to mind is the meme of the beautiful dog with a giant pizza in front of him <3

What about fitness? (berkeley.edu)

Microevolution

 

 

Microevolution is the change in inherited traits of a population from one generation to the other. This prediction from the idea of descent with modification leads to an accumulation of changes and ultimately a transformation of a species over a period of time. The definition comes from the book "Primer to Evolution” that we have access to in our evolution class. When I think of the idea of descent with modification, I immediately think of the prediction that a species changes over time. It is still fresh in my mind from a previous assignment discussing beak size in a bird population. I think it is my favorite because it makes the most sense to me. The change from one generation to the next is usually subtle but when natural selection is a strong factor at play, we can observe the evolutionary changes in relatively short periods of time.

The idea of evolution itself can be overwhelming and confusing as you aren’t sure what can fall under that theory as our understanding is changing over the years. The example that our book gives us covering the Three-spine Stickleback fish is a great one to read. It explains the differences seen between generations and even covers a 1964 experiment showing how quick the stickleback fish could evolve.

 

A stickleback fish is one characterized for their “armor plates” along their body. Evidence has shown over time that these fish have a reduction in their armor plates and in some cases even a complete lack of pelvic spines. This species adapts to its environment; whether it be streams, lakes or pelagic and benthic habitats. The fish’s body shape and coloration and diet are all different depending on their environment. The 1964 Great Alaska Earthquake that changed the region and quite literally lifted islands further out of the ocean created a phenomenon that showed us just how quickly the Stickleback fish could evolve. According the the book, the stickleback fish that colonized the new freshwater pounds evolved to form similar characteristics of the stickleback found in continental freshwaters in just 50 years! While this seems like close to a lifetime for us, this period of evolution happened in just a blink of an eye for life on earth.

I found microevolution so interesting because not only does it make sense, but it is the first thing that we were taught about evolution in middle school biology. It is an idea that sort of wraps a neat little bow around this aspect of evolution. It can get a little confusing when you add genetics into the mix, but overall it is a prediction that is based off of so much evidence scientists have uncovered throughout the years. Microevolution will continue to happen throughout our lifetime and long after we are gone.

Book: Primer to Evolution

https://www.k-state.edu/biology/p2e/index.html