Transcript Lamarck
Lamarck • Early theory of evolution • Theory of “acquired characteristics” • He said: –the more an animal uses a body part the more developed that part gets –the characteristics an animal develops can be passed on to its offspring Lamarck • Problems with this idea? –Development does not affect genes –Only genes are passed on –What if an animal were to lose a leg? Charles Darwin • Worked on developing a theory of evolution for most of his life • Started as a naturalist on the HMS Beagle • Sailed to South America and the South Pacific Galapagos Islands • Especially important in his travels • Saw animals that were unique, but similar to animals elsewhere Darwin (cont’d) •He thought that animals could change over time but didn’t know how •Did lots of reading, studying, collecting and experimenting Thomas Malthus •A sociologist friend of Darwin’s •Figured out that the human population could grow faster than the food supply •Therefore, some people wouldn’t get enough food and would not survive An idea is born… •Darwin expanded Malthus’s idea to all living things An idea is born… •Darwin expanded Malthus’s idea to all living things •He said that all individuals must struggle to survive An idea is born… •Darwin expanded Malthus’s idea to all living things •He said that all individuals must struggle to survive •This must be true or we’d be overrun with creatures that produce large numbers of offspring The struggle •Food •Space •Shelter •Mates •Escape from predators The struggle •Food •Space •Shelter (Key idea!) •Mates •Escape from predators • Only those that are successful go on to produce offspring and NOT ALL ARE SUCCESSFUL Darwin’s Experiments • Pigeon breeding • Saw that there was variation in the populations Variation means individuals were different in their characteristics • He could create offspring with a certain trait by breeding two birds with that trait • This is artificial selection Darwin’s Theory •Hypothesis: there was a force in nature that worked like artificial selection Darwin’s Theory •Hypothesis: there was a force in nature that worked like artificial selection –It allowed only individuals with certain traits to reproduce and they produced offspring with those same traits Darwin’s THeory •Combining this with the idea of struggle you get natural selection: Darwin’s THeory •Combining this with the idea of struggle you get natural selection: –Organisms vary in their traits which makes them vary in their ability to be successful in the struggle Darwin’s THeory •Combining this with the idea of struggle you get natural selection: –Organisms vary in their traits which makes them vary in their ability to be successful in the struggle –Those traits that make you successful are passed on and are more common in the next generation Alfred Wallace • came to the same conclusion as Darwin after studying the islands of Indonesia Evolution is a theory •In science, this means there is overwhelming evidence to support it Evolution is a theory • In science, this means there is overwhelming evidence to support it • Very slow, so hard to observe because humans don’t live very long –Evolution can take thousands or millions of years –Though, for some organisms we can see it Evolution is a theory • Most scientists accept evolution as true • Some people disagree because of their faith and offer alternative interpretations of the data Evolution 1. 2. There is variation in the population More offspring are produced than can survive 3. Those individuals with the better traits survive and have more offspring 4. Those offspring inherit the good traits 5. The good traits becomes more common in the population What does evolution look like? •Let’s start with a population that is equally blue and green The green dots are more successful than the blue All the green reproduce and have 2 offspring then die Only 1/5 of the blue reproduce and have 2 offspring then die The next generation looks like this….. If the same thing happens again…the next generation looks like this….