Blog 3: reflection post fitness

 How do you define fitness? 

There are many ways to go about defining fitness and definitions can vary, but there are underlying themes that play into the concept that can help us define its meaning. A simple way of interpreting it is the actual strength of natural selection on different variables being measured within a population. Natural selection and fitness go hand in hand and fitness play into the concept of natural selection immensely. It can be assumed that fitness plays into the particular phenotype of the gene pool for the following generations. Fitness in itself is a quantitative measure of natural selection and it quantifies an individual's reproductive success within the population. It also contributes to the average in a gene pool of the following generation by individuals of a specific phenotype in a population's environment. Fitness is used to compare one phenotype to another phenotype. Fitness has many contributing factors but it is the organism's ability to thrive and reproduce in a given environment. 

Also, how would you measure fitness in a natural population? 

Provide a concrete example; i.e., be specific about what organism you have in mind and describe the concrete steps you would take to quantify fitness.

There are many ways to measure fitness within a population in an experimental setting where everything is accounted for and mapped out. One can measure absolute fitness which is the ratio of a given genotype before and after selection. Or one could measure relative fitness which is the differential reproductive success. Measuring fitness can also be accomplished by looking at the reproductive success of individuals. Measuring the organism's ability to survive and reproduce will indicate if they have a high fitness or a low fitness, the environment will create pressures that influence these values. By measuring the numbers associated with phenotypic genetic components as well as reproductive success, we can start to see the genetic contribution to the next generation. But the truth is, fitness can not be measured in most studies. We can make assumptions but the measuring is easier said than done. But it's important to also acknowledge that fitness is not indicated by the total number of offspring but rather by the proportion of subsequent generations that carry on an organism's heritable genetics. An example that can be studied regarding fitness is the case study involving dark and light fur on mice. The fitness of the population was studied because of the fact that the darker coat color increases crypsis when in the dark leaf litter of the environment. But the fitness is determined by the environment that the mice were living in, the land might be dark or light and provide the mice with an advantage. The light-colored mice thrived better on the beach and were hunted less allowing them to have better reproductive success. The dark and light mice could be counted and studied to understand which trait was more beneficial regarding numbers. There are advantages and disadvantages to each fur color, and the environment determines which one is more beneficial. The one that is more beneficial will have a higher fitness because of the quantitative representation of natural selection. 

Sources;

Primer to evolution