Blog Post Module 3: Reflection Prompt

 I would define fitness in the context of evolution as an organism's ability to survive and reproduce in its environment. It isn't really physical strength in this context. In a natural population you could measure fitness by observing the number of offspring produced by as many individuals in a species as you can find and then calculating the average number of offspring born. To account for the survival aspect you could use phenotype and specific visible markers to estimate the age of the oldest individuals in the population. If you know approximately how long most organisms in a population survive then you can compare that with the average number of offspring to try and quantify or better understand fitness in that population. Fitness is also going to be impacted by specific aspects of a habitat such as space, food availability, water availability, competition, predation, etc. At times there may be a tradeoff where exerting energy in one area may lead to a decrease of success in another area. For instance, octopuses typically lay between 50,000 and 80,000 eggs. However, the average life span of the giant pacific octopus is only 3-5 years. It's not very long at all. Therefore, they sacrifice survival to some extent, in order to produce a large amount of offspring and create the best chance for continuing the species. There isn't enough energy for both. Those specific factors would also be important to observe and study. You would also need to look at the genotypes of individuals in the population and see which ones lead to reproductive/survival success. According to research I've done, fitness can also be the relative probability that a genotype will reproduce. In that case, mean absolute fitness can be calculated by the equation W=pW1+qW2 where p is the frequency of genotype 1, q is the frequency of genotype 2, and W1/2 are the absolute fitnesses of genotypes 1 and 2. Mean individual fitness is calculated by P(1)+(1−P)(0) = P

(Article title: Fitness and its role in evolutionary genetics, Author: H. Allen Orr, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2753274/, August 10, 2009)

In a circumstance where chipmunk fitness is being studied, you would look at and measure the space/ habitat that these specific chipmunks inhabit. Do they have enough space to continue reproducing and diversifying? You would also want to come to some conclusion about how many chipmunks there are approximately in this population. Hopefully, the habitat you choose is manageable enough in size to be able to get a pretty accurate population size. A larger population would generally mean more genetic diversity and thus a greater chance to reproduce and be successful. A smaller population typically means less genetic diversity. Because population fitness heavily depends on the diversity of alleles in a population, this is very important to study. I am not exactly sure how to incorporate factors such food/water availability, competition, etc. but those could definitely impact a population's fitness. If there is a drought or insufficient food for example, then those chipmunks would not be able to survive and therefore reproduce. So I guess what I'm saying is that it depends on the specific genetic and environmental circumstances of that time. You could also observe chipmunk nests/burrows around the area and get an idea of how many young a typical chipmunk gives birth to. To be more accurate and use the formulas, genetic studies would need to be conducted. You couldn't observe those things through studying in the habitat alone. Phenotype can't always give you the correct genotype.

(https://hugepdf.com/download/download-two-species-of-chipmunk-are-being-studied-in-a-national-park-the_pdf, April 11, 2018)