ShabelEvol5 - Bio 1B Summer 2009 Evolution Lecture 5...

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Bio 1B, Summer 2009 Evolution, Lecture 5 Professor Alan Shabel Page 1 of 1 Updated on 29 June 2009 EVOLUTION, LECTURE 5: NATURAL SELECTION AND ADAPTATION (487–498, 523–525) The normal distribution in statistics describes a data set that clusters around a mean in a bell- shaped curve ( bell curve ), and many quantitative organismal traits are distributed normally within a population. Natural selection alters the distribution of heritable traits in a population in three main ways, depending on which phenotypes are favored: directional selection , stabilizing selection , and disruptive selection (see Figure 23.13). I gave examples of each of these modes of selection in lecture: an example of directional selection is the high mortality of small-bodied swallows after a frigid winter; an example of stabilizing selection is the higher mortality suffered by human newborns at the extreme ends of the body mass spectrum; and an example of disruptive selection is the relatively lower fitness of...
View Full Document

This note was uploaded on 07/04/2009 for the course BIO 1B taught by Professor Carlson,mischel,power during the Summer '07 term at Berkeley.

Ask a homework question - tutors are online