Look at these pretty birds - Sexual Selection

Sexual Selection is the reproductive advantage that some individuals have over other individuals of the same sex within the same species. Therefore, sexual selection can have a profound effect on the fitness of an organism. Organisms partake in sexual selection intrasexually by male-male competition or intersexually by female choice. In order for a male to find a mate, they will partake in endurance contests, fights, and even infanticide, all in order to increase access to mates any way they can. However, sexual selection can end up causing males to spend more time attracting a female mate rather than spending time on obtaining food and watching out for predators. Some of the adaptations male birds have do not always give a competitive advantage, but they can be directly selected for by females, which then ensures their reproductive success in passing on their genetic material. In this circumstance, sexual selection to find a mate becomes a trade-off.

Some of the most beautiful birds in the world live in eastern Indonesia, Papua New Guinea, and eastern Austrailia, and are called the Birds of Paradise. These birds are a great example of sexual selection. Watch this video below and think about how the birds partake in sexual selection, why they act the way they do, and how it might be considered a trade off.

https://www.youtube.com/watch?v=W7QZnwKqopo&feature=youtu.be

Why does this matter??

Why do people spend their whole lives studying evolution and natural selection? Studying evolutionary biology tells us a lot about where we came from, as well as where we are going, as a species. Additionally, it tells us a whole lot about how we got to the vast diversity of organisms we see today. Each organism didn’t just happen to show up by chance. They changed and kept on evolving over many years to get where they are today. By studying evolution, we can use this information in many practical ways such as to see how organisms react to environmental change, how we can most effectively manage conservation efforts, and to learn more about antibiotic resistance.

With all that being said, why does our misconception matter? By acknowledging the fact that the the fittest organisms in a population are NOT always those that are strongest, healthiest, fastest, and/or largest, we get to see how their populations have evolved over time, and how to study what factors are most important to that species in order to reproduce and survive throughout generations. This has many implications that will ultimately help us in conservation efforts of species that are threatened or endangered.

If you are feeling like you get this concept or want to learn more, there was a great article published in Nature Reviews Genetics called “Fitness and its role in evolutionary genetics.” This is just one example of why studying evolution and fitness is important. Follow the link here: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2753274/

Literature cited:

Orr H.A. Fitness and its role in evolutionary genetics. Nat. Rev. Genet. 2009;10:531–539

Natural Selection Is Not Perfect: Trade Offs!

Referring back to the Peacock example, a female peacock chooses her mate based on her attraction to the pattern and length of the male's tails.  However, the prettier and longer tails come with a reduced ability to camouflage and escape from predators.  Common predators are wild dogs, raccoons, and tigers.  The ability of a male to pass on their genes to offspring outweighs the ability of the male to escape predators, so the presence of the bright colored tails remains constant.

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.

Animals, World. "Do Peacocks Have Any Predators?" AnimalAnswerscouk Everything You Need to Know about Your Favourite Animals. World of Animals, 13 Aug. 2014. Web. 03 Mar. 2016.

https://www.pinterest.com/pin/559642691166212608/

https://fhaiddotcom.wordpress.com/category/pretty/

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
• 
• 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