History of Evolution Chapter 9

Which came first?

Recall: Hutton & Lyell’s Contribution  Profound geologic processes of today are the same as in the past

Recall: Lamarck’s Contribution  Life evolves as environment changes  Acquired traits can be passed to offspring  Use and disuse – use it and it gets better/bigger, don’t and it gets worse/smaller  Thus, no extinction exists

Recall: Malthus’ Contribution  Populations produce more offspring than can possibly survive to reproduce  Remember carrying capacity?

Recall: Mendel’s Contribution  Traits are passed from parents to offspring  There is variation of traits within populations

Darwin Connects the Pieces  Collected thousands of plants & animals on Beagle voyage (ended October, 1835) Each had wondrous adaptations  On the Origin of Species published November, 1859

Observation  Members of a population vary extensively in their characteristics no two individuals are exactly alike (DNA)

Observation  Much of this variation is heritable

 For any species, population sizes would increase exponentially if all individuals that are born survived and reproduced successfully Observation

 Resources are limited

Big Idea #1  Production of more individuals than the environment can support leads to a struggle for existence among individuals of a population, with only a fraction of their offspring surviving

Big Idea #2  Differential survival and reproduction Survival depends on inherited traits; individuals whose inherited traits give them a high probability of surviving and reproducing are likely to leave more offspring than other individuals

Big Ideas 1 & 2 = Big Idea #3  This unequal ability of individuals to survive and reproduce will lead to a gradual change in a population  Favorable characteristics accumulate over generations

Natural Selection  Organisms better suited to the environment are more likely to survive and reproduce than organisms less suited to the environment

Natural Selection

Natural Selection Leads To Diversity

Therefore…  A non-chicken ancestor laid an egg in which a genetic mutation occurred and developed over many generations into Earth’s first chicken.  Video Video

 5 Fingers of Evolution 5 Fingers of Evolution