Descent With Modification A Darwinian View of Life

Descent With Modification: A Darwinian View of Life

Warm-Up 8/24/2016 Explain the process of natural selection. Identify one example of evolution that you are familiar with.

What Evolution Is • Descent with modification • Change in genetic frequencies over time Change with inheritance • From http: //evolution. berkeley. edu/evosite/evo 101/IIntro. shtml

What’s a theory? • In your own words, describe the concept of a theory. Give another example of a theory in science?

History of Evolution • Aristotle (384 -322 BC) l l Scala naturae- life forms can be arranged on a scale of increasing complexity. Life was fixed, perfect, and permanent • Natural theology (1700 s) l Perfect species were individually designed by God. • Linnaeus (1707 -1778) l l Taxonomy: grouping and naming of organisms that are similar; binomial nomenclature Nested, not linear

What Lamarck proposed • 1744 -1829 • The environment gives rise to changes in animals • Use and Disuse theory: animals could adapt to their environment

Inheritance of Acquired Characteristics • Modifications acquired during an organism’s lifetime could be passed on to their offspring.

Charles Darwin

Where Darwin Went He was gone for 5 years!

What Darwin saw

Development of Theory of Natural Selection • Darwin observed 12 different species of finches collected from Galapagos islands • Beaks were different. . . why?

Thomas Malthus “An Essay on the Principle of Population”

Descent with Modification • Darwin’s famous “Tree of Life” sketch from his notebooks • Proposed that there were common ancestors for living things • Current forms were descended • from ancient forms, and that ancient forms had to have experienced extinction Proposed that this change that occurred took place over long periods of time; gradual changes added up to more significant ones

Observation #1 • Variation exists among members of a species.

Observation #2 • This variation is inherited.

Observation #3 • There are limited resources in the environment. There is a struggle for survival.

Observation #4 • Organisms with favorable traits are more fit, thus they leave behind more offspring than those who are less fit.

Observation #5 • These favorable traits persist in the population and will become more frequent.

Result: • Differential reproductive success leads to change in favorable traits among generations

In sum… Genetic Variety + Environmental factors Natural Selection