Does Natural Selection act on Does Natural Selection act on Phenotypes or Genotypes?Phenotypes or Genotypes?

http://fig.cox.miami.edu/cmallery/150/unity/c1x17b-finches.jpg

The Grant Finch StudyThe Grant Finch Study Peter and Rosemary Grant have Peter and Rosemary Grant have

studied and documented evolution studied and documented evolution of finch beaks on the Galapagos of finch beaks on the Galapagos Islands.Islands.

Changes in habitat and seed Changes in habitat and seed availability on the environmentally availability on the environmentally turbulent islands favored some turbulent islands favored some finches and not others. Successive finches and not others. Successive generations of the birds showed generations of the birds showed different beak shapes.different beak shapes.Columbiajournalist.org.science_reporting/2005/article.asp?...lid=606

Figure 1: Histogram of distribution of beak depth of medium ground finches on Daphne Major, before and after the drought of

1977 (Grant 1986). Reprinted by permission of Princeton University Press. http://fig.cox.miami.edu/cmallery/iso/unity/case_study.htm

Individuals within a population Individuals within a population vary in their traits:vary in their traits:

Some variable traits are heritable; Some variable traits are heritable; they are passed on to offspring:they are passed on to offspring:

http://scied.fullerton.edu/biol409/session4/elaborate_b.html

More offspring are produced than can More offspring are produced than can survive because of limited resources survive because of limited resources

such as food and nesting sites:such as food and nesting sites:

Figures 3a and 3b: Figure 3a shows the population of Geospiza fortis before and after the drought in 1977. Figure 3b demonstrates seed abundance on Daphne major before and after the drought. http://scied.fullerton.edu/biol409/session4/elaborate_b.html

Individuals with advantageous Individuals with advantageous traits will survive and reproduce:traits will survive and reproduce:

Figure 1: Histogram of distribution of beak depth of medium ground finches on Daphne Major, before and after the drought of

1977 (Grant 1986). Reprinted by permission of Princeton University Press. http://fig.cox.miami.edu/cmallery/iso/unity/case_study.htm

Review Time!Review Time!

Natural selection acts on phenotypes Natural selection acts on phenotypes rather than genotypes of an organism: rather than genotypes of an organism: it’s actions change the allele it’s actions change the allele frequencies in a population.frequencies in a population.

Variation within a species increases the Variation within a species increases the likelihood that at least some members likelihood that at least some members of a species will survive under changed of a species will survive under changed environmental conditions.environmental conditions.

The entire individual is the target of The entire individual is the target of natural selection:natural selection:

The of the individual is The of the individual is NOT the target of NOT the target of selectionselection

Columbiajournalist.org.science_reporting/2005/article.asp?...lid=606

Which Figure or Figures Would Which Figure or Figures Would Support These Statements?Support These Statements?

Individuals within a population Individuals within a population vary in their traitsvary in their traits

Diversity of species increases Diversity of species increases the chance that at least some the chance that at least some organisms of that species organisms of that species survive major changes in the survive major changes in the environmentenvironment

Internet Websites and Image Internet Websites and Image ResourcesResources

Columbiajournalist.org.science_reporting/2005/article.asp?...lid=606

http://fig.cox.miami.edu/cmallery/iso/unity/case_study.htm

http://fig.cox.miami.edu/cmallery/150/unity/c1x17b-finches.jpg

http://scied.fullerton.edu/biol409/session4/elaborate_b.html