Example of Biological Fitness

Fishing is a major source of selection in aquatic environments.  When a group of fish gets caught in a net, there ability to survive is is partially dependent on size.  Large fish are not able to escape, where as small fish are able to swim through the net, and continue living and reproducing.  The fitness of the small fish is higher than the big fish.  This is a prime example showing that having the highest fitness does not mean one is the biggest or strongest organism.  

Rincon, P. (2005, February 20). Fish Shrinkage Threatens Survival. Retrieved March 03, 2016, from    http://news.bbc.co.uk/2/hi/science/nature/4281171.stm 

Example of Biological Fitness

                

Female peacocks choose their mates based on their attraction to male peacock’s tails. Therefore, male peacocks with big, colorful tails are likely to reproduce more than those without extravagent tails. This indicates, referring back to the definition of fitness, that male peacocks with longer tails will have higher fitness in the population. This is also an example of sexual selection.

Burgess, Stuart. "Peacock Tail Beauty and Problems with Theory of Sexual Selection." Answers in Genesis. Journal of Creation, 15 Aug. 2001. Web. 03 Mar. 2016.

Picture 1: http://thebossjflores.weebly.com
Picture 2: http://mindingtheminis.com/category/peacocks/

Misconception: The fittest organisms in a population are those that are strongest, healthiest, fastest, and/or largest.

By looking at the misconception, it is apparent how the average person would agree with the statement. If you have no previous experience with fitness in terms of its biological context, one could assume that fitness is referring to someone’s health and strength. However, fitness is the ability of an organism to pass on its genes to the next generation:

1. A higher fitness means that an organism is successful at leaving viable offspring
2. A lower fitness means that an organism is not successful in passing on its genes to the next generation of its offspring. 

If this concept is still confusing, you should watch this Khan Academy video for some clarification:  

Now that we know what fitness means in terms of biology, it should be evident that our statement is false. As a society, we have anthropomorphized what it means to be “fit.” In nature is that it’s not always the strongest, fastest, healthiest, and largest organisms that have the highest rates, or success, when it comes to reproduction and the passing on of their traits. Throughout our blog, you will see various examples and trade-offs that show how evolution has caused differential fitness across numerous species.  

Is biological fitness the same as physical fitness?

Biological Fitness: 

• Definition: The extent to which an individual contributes genes to future generations, or an individual’s score on a measure of performance expected to correlate with genetic contribution to future generations (such as lifetime reproductive success)
• Example: Two mice within a species have different fur color, the dark mouse blends in better with surrounding, thus avoiding being eaten. As a result, the darker mouse survives longer and produces more offspring, making it more fit
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• http://goose.ycp.edu/~kkleiner/ecology/lectureimages/EvolEcolgy/Rockpocketmice.jpg

Physical Fitness: 

• The condition of being physically fit and healthy
• "Definition of Fitness in English:." Fitness: Definition of Fitness in Oxford Dictionary (American English) (US). Oxford University Press, n.d. Web. 03 Mar. 2016.
• Example: One male has more arm muscle and is stronger
• 
• https://beyondinsurance.files.wordpress.com/2012/08/strong-vs-weak-cultures.jpg

There is a significance difference between the two definitions of fitness, and understanding how they differ is crucial to one's understanding of natural selection. Biological fitness is what is referred to in natural selection so let's keep that in mind as we move forward in our quest for knowledge.

Natural Selection:

• Definition: Variation in the genotype that increase an organism's chance of survival and procreation are preserved and multiple from generation to generation at the expensive of less advantageous ones
• The Editors of Encyclopedia Britannica. "Natural Selection | Biology." Encyclopedia Britannica Online. Encyclopedia Britannica, 15 May 2014. Web. 03 Mar. 2016.
• In common terms: Heritable differences in an organism (appearance, behavior etc) that increase its ability to reproduce become more common in each subsequent generation