APBI 200 Lecture : Biol 121- 2010.03.12- Evolution- Natural Selection (Ch. 24).docx
Document Summary
Summing up the 4 steps in only 2. Credit for natural selection" is given to darwin. Individuals with certain heritable traits are more likely to survive + reprod. Natural selection occurs when indiv with certain char produce more offspring than do indiv w/o those characteristics. Evolution change in genetic char of a pop over time is the outcome of these four steps. Populations must change over time for evolution to occur. Evolution by natural selection occurs when: heritable variation leads to , differential success in survival and reproduction. Evolution can be defined as a change in allele frequencies in a pop over time. Two alleles for a gene for wing colour, one producing dark and other light. Predation by birds they eat dark-winged individuals much more readily than they can find and eat light-winged individuals if have light-coloured bark. Therefore, predation by birds causes natural selection on wing colour leading to differential success.
