Lecture 15

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

Info iconThis 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. Baby weight in humans – too big or too small die, middle survives
Background image of page 1

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

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

This note was uploaded on 03/12/2012 for the course BIO 121 taught by Professor Minchella during the Fall '10 term at Purdue.

Page1 / 2

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

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online