Lecture 15 - Bio 121 Lecture 15 adaptive evolution the role...

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

View Full Document Right Arrow Icon
Bio 121 Lecture 15 – adaptive evolution: the role of natural selection A. Introduction a. Natural selection is always operating in a population b. Selective pressure always operates to disturb hardy-weinburg c. Depends on mode of selection and strength of selection B. Modes of selection a. Directional selection a.i. One extreme phenotype is favored over the other a.ii. Shifts phenotype distribution of survivors in one direction a.iii. Could lead to gradual replacement of one allele out of the gene pool a.iv. Practiced by plant and animal breeders b. Disruptive selection b.i. Both extremes are favored over the intermediates b.ii. Selection divides the population into 2 types and intermediates have lowest frequency b.iii. Juvenile black bellied seed crackers. Long beaks and short beaks, no medium c. Stabilizing selection c.i. Intermediates are favored over extreme c.ii. Increases frequency of average phenotype and reduces variation around that phenotype c.iii.
Image of page 1

Info iconThis 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