How Do Darwin and Lamarck’s Theories Compare?

Evolution What is evolution? A change over time.

Examples of Evolution

Two Main Theories of Evolution 1. Acquired Characteristics 2. Natural Selection

Acquired Characteristics Introduced by Jean-Baptiste Lamarck(1744-1829) Believed living things on Earth had changed gradually over time, were still changing, and would keep changing – not believed by most! Living things change so they have a better chance of surviving in the environment. Said animals were “selecting themselves” to survive. Species never went extinct; they just kept changing.

Theory of Acquired Characteristics States that if an individual wanted to change something about the way its body worked, it could. When that individual reproduced, the changes that it had made during its lifetime would be passed on to its offspring.

Examples of Lamarck’s Theory of Acquired Characteristics Giraffes’ long necks and elephants’ trunks Giraffes that needed longer necks would use it more and stretch it out. Their babies would then have longer necks too, and they would then stretch them even more and pass on even longer necks to their babies.

Why Lamarck’s Theory Is Wrong Physical injuries are not passed to offspring Skills are not passed to offspring Fossil evidence shows organisms have gone extinct GENETICS!

Theory of Natural Selection Introduced by naturalist (person who studies plant and animals by observing them) Charles Darwin (1809-1882) Studied animals, especially finches and tortoises, in the Galapagos Islands Also believed living things continuously change to increase their chance of surviving in their environment. Believed nature selected organisms with the best traits to survive and organisms could become extinct if they were not well adapted to their environment.

Theory of Natural Selection Darwin believed organisms only pass on the traits they themselves are born with. All organisms, even of the same species, are slightly different from one another. These differences are called variations. Certain variations make some organisms better suited to their environment than others. Since the ones that are better adapted have a survival advantage, they also live longer and are able to reproduce more. Every time they reproduce they pass their successful traits down to their offspring. “Survival of the Fittest”

The Principles of Natural Selection 1. Organisms produce more offspring than can survive. 2. Variations occur among individuals of a species. 3. Some variations are passed to offspring. 4. Some variations are helpful. Individuals with helpful variations survive and reproduce better than those without these variations. 5. Over time, the offspring of individuals with helpful variations make up more of a population and eventually may become a separate species.

Conclusion