Sexual Selection

I think that sexual selection is one of the most interesting topics in all of biology. First, studyign this topic helps to illustrate that natural selection is much more than "survival of the fittest". Second, many of the traits produced by sexual selection are particularly bizzare. Finally, I think that it is fun to use what we have learned about mate choice in animals to helping us to understand human behavior.

Expected Learning Outcomes

By the end of this course a fully engaged student should be able to

- discuss the critical difference between males and females and discuss how this difference influences differences in behavior and morphology between species.

- discuss why sexual selection is just a subset of natural selection

- discus why females should be choosier about who they mate with than males

- discuss why males often compete with other males to fertilize eggs of females

- compare and contrast male-male competition in species with internal fertilization and species with external fertilization

- describe the studies used by scientists to see if females are capable of choosing the best males

- discuss how females can determine which is the best male

- discuss why the variation in female reproductive success is much less than the variation in male reproductive success

- discuss how you would use sexual selection to help you understand human behavior

Past Exam Questions (answers at the bottom of the post)

1. Why are females choosier than males about who they mate with?
(a) female gametes are much more expensive than male gametes
(b) male gametes are much more expensive than female gametes
(c) in some species, males are larger than females
(d) in some species, males compete to mate with the female
(e) c and d

2. Why should females prefer to mate with the oldest males?
(a) because they can pass on good mating genes to their daughters
(b) because they can pass on good survival genes to their sons
(c) because the can pass on good survival genes to their daughters
(d) a and c
(e) b and c

3. Why might females sometimes cause male-male competition to occur?
(a) to assure that she mates with the oldest male
(b) to assure that she mates with the most symmetric male
(c) the male who wins the fight is likely to have “good genes”
(d) a and c
(e) a, b, and c

Further Reading

Here is a link to a website that a student sent to me last year called "The 30 Strangest Animal Mating Habits" http://www.neatorama.com/2007/04/30/30-strangest-animal-mating-habits/

Take a look at this and see if you can relate what the animals are doing to some of the theories that we have talked about in class.

Here is a link to a youtube video showing the mating display of lyrebirds. I was lucky enough to see a lyrebird doing its mating display when I was a kid living in Australia. There was a professional nature photographer who had been hiking around the bush for a couple of weeks waiting to see the display and he was pissed that my Dad and I were able to see the display after spending only about an hour in the woods. What do you think is going on with the lyrebirds?

http://www.youtube.com/watch?v=VjE0Kdfos4Y

Here is a link to the Powerpoint Presentation I prepared for this topic.

http://www.slideshare.net/secret/CG2HHvtrLA1KwL

Answers. 1. a, 2. e, 3. c

Here is a link to an interesting article that I just discovered on an ex-student's Facebook page. Biology is Cool!!!!!

Male spider snaps off own genitals inside female to fertilise her remotely, while being eaten.

http://blogs.discovermagazine.com/notrocketscience/2012/02/01/male-spider-snaps-off-own-genitals-inside-female-to-fertilise-her-remotely-while-being-eaten/