How was Darwin’s Theory Shaped by other scientists? Lamarck (1744-1829) Darwin (1809-1882)

Lamarck’s Theory of Evolution: Inheritance of Acquired Characteristics An organism will change during life in order to adapt to its environment. Those changes are passed on to its offspring. Change is made by what the organisms want or need. Body parts that are not used, gradually disappear. “pre-determined plan”

Lamarck Believed… Giraffes stretched their necks to reach food. Offspring and later generations inherited the long necks.

Lamarck’s Theory of Evolution: Recognized that all living things changed over time, and have descended from other species.

Lamarck’s Theory of Evolution: Laws of Use and Disuse: Organs / Structures used would remain strong and functional, while those not used would disappear.

Lamarck’s Theory of Evolution: Inheritance of Desired Traits: Traits acquired due to adaptations to the environment were passed on to offspring

August Weismann Cut off the tails of mice and allowed the mice to mate. The offspring were born with tails. DISPROVED Lamarck’s theory.

Considered the “father” of evolution. Darwin Considered the “father” of evolution. Charles Darwin traveled to the Galapagos island, an uninhabited environment, where he studied evolution (Darwin’s Finches)

Darwin Believed Organisms (even within species) are all different and those which happen to have variations that help them survive in their environments. Those that survive have more offspring. Offspring are born with their parents’ helpful traits, and they reproduce, and that trait makes up more of the population.

More on Darwin… Individuals that are not well adapted, die off. example: Some Giraffe’s had short necks, some had long necks. When lower food sources became scarce, giraffe’s with longer necks survived because they could get food. Ex2; Elephants and trunk size/water

Darwin’s Theory of Evolution Natural Selection: Individuals with favorable traits are able to survive and reproduce. Nature controls which traits are favorable.

How They Agreed Both thought life had changed gradually over time (and still changing) Living things change to be better suited (Adapted) to their environments All organisms are related Life evolved from fewer simpler organisms to many, more complex ones

Why we believe Darwin Weisman’s experiment. Other observations: people who exercise, run a lot, eat well and generally healthy and fit do not have children who are inherently healthy and fit, the children have to work at it. Gene sets that are in a population determine the traits there are. Genes sets are determine by which individuals die and which survive.