IB31Lecture+3+Outline+Sp08 - IB 31 Sp 2008 Jan 29 2008...

Info icon This preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
IB 31, Sp. 2008 Jan. 29, 2008 Caldwell, Evolution and Natural Selection I Central to almost every aspect of Modern Biology is Evolution based on the concept of Natural Selection, as formulated by Darwin and Wallace, and substantiated and modified by later scientists. To understand modern behavioral biology, it is essential that you understand these processes. This will be old hat for some of you, but it is so important to understanding behavior that I want to make sure that the class starts on a solid foundation. Therefore, if you have had this before, please bare with me. If you are having difficulty with evolutionary concepts, try logging onto our UC Berkeley website, Understanding Evolution: . I. EVOLUTION, as we now understand it, is a change in the genetic composition of a population. (For our purposes, a population is a group of potentially interbreeding individuals.) Usually, the changes we are concerned with are in the relative frequencies of particular forms of a gene. Different forms of a gene are called ALLELES. For example, in humans, a particular gene may be one of many involved in the production of the skin pigment melanin. The normal genetic instructions at this locus promote melanin production. This is called the “normal” allele. A defective set of genetic instructions at this same locus might block pigment production and produce albinism. If you inherited two copies of this allele, you would be an albino. (Remember from your basic biology, we have two sets of genetic instructions carried on pairs of autosomal chromosomes. Each chromosome of a pair has one copy (allele) of a particular gene found at a particular location on that chromosome.) One normal allele is sufficient to produce melanin. Typically, the frequency of albino alleles is very rare in human populations - much less than 1%, and there are very few albinos. In fact, there may be some selection against this condition due to UV exposure causing skin and eye cancer. However, if for some reason albinos in a population were favored and were more likely to reproduce, the allelic frequency of the albinism form of the gene would increase (Cuna Indians of the San Blas – moon children), there would be more albinos and we would say that the population had evolved - there was a change in gene frequency! Evolution can also occur when there are changes in the structure of chromosomes and the arrangement of genes on them, affecting how genes are expressed and inherited or how genes are switched on and off, but for our purposes, we will be primarily concerned with changes in gene frequencies. II. Lets look at one well-documented case of evolution - a rare instance where we have been able to observe the process in action - INDUSTRIAL MELANISM. This is a classic example used in many text books, but I want to concentrate on how we deduce the mechanisms underlying evolutionary change.
Image of page 1

Info icon This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern