An understanding of the process of natural selection helps us to understand the amazing diversity of life on the earth.
Expected Learning Outcomes
By the end of the course a fully engaged students should be able to
1) define the process of natural selection
2) distinguish between the patterns of stabilizing, disruptive, and directional selection and provide examples of each pattern
3) describe how the process of natural selection has produced a trait that is an adaptation to a particular environmental condition.
4) explain why organisms are not expected to be perfectly adapted to their environments
5) discuss the conditions that would cause natural selection to stop
6) explain why natural selection is expected to produce selfish traits
Readings
Natural selection http://www.eoearth.org/article/Natural_selection
Here is a link to a website from UC Berkeley that might be useful to take a look at-
http://evolution.berkeley.edu/evolibrary/article/evo_25
I know you haven't reviewed the syllabus in class yet (and as such, had the chance to formally amend this), but the syllabus actually lists your blog from last spring's 1404. That being said, I imagine not many of us have actually found the correct blog yet. I hope we weren't expected to complete the assigned reading before class tomorrow.
ReplyDeleteIn regards to the reading itself, from what I understand, both directional and disruptive selection are expected to occur due to prevalence of an extremity in a given trait. However, two different phenotypes will remain prevalent after disruptive selection occurs (the "normality" and an extremity, two extremities, whatever. Emphasis is on bimodality, yeah?), as opposed to just one after the shift from directional selection. Is it safe to say that it requires more "effort" on natural selection's part for two traits to remain phenotypically prevalent, thus making disruptive selection a more rare occurance that directional? Or am I just talking out my ass here, for lack of a better way to put it? If the former is true, then would it be expected for one of the traits brought about by disruptive selection to eventually give way to directional/stabilizing selection, or is this all entirely situational, able to go either way, completely dependent on what the environment calls for?
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ReplyDeleteHi Bobby, Thanks for your comment. Sorry I have been slow to respond.
ReplyDeleteDisruptive selection is by far the least common pattern of selection. Perhaps the best example is the evolution of oogametes from isogametes which is something that we will talk about later in the semeter. It is possible that disruptive selection can then be followed by directional selection taking the two new distributions farther away from each other. Does this make sense?
in one of the expected outcome we need to know how natural selection has produced a trait that is an adaption to a particular environmental condition. for my understanding, natural selection increases fitness of actor. therefore an individual with an advantageous trait will survive and reproduce more, passing on this trait to future generations. will this be an acceptable explanation to this expected outcome?
ReplyDeleteJennyfer, What I meant here was for you to be able to explain (1) why a particular trait provided a survival or reproductive advantage and (2) how the process of natural selection caused the genes coding for that trait to become most common.
ReplyDeleteFrom the lecture on sexual selection there are many examples- how did female frogs come to mate with males with the deepest croak, how did male elephant seals become so much larger than females, etc.