Lamarck vs. Darwin

1. Lamarck vs. Darwin

2. Theories of Evolution: Lamarck & Acquired Characteristics • Jean Lamarck-French naturalist, challenged the idea of fixed species (1809) • Proposed that organisms evolved in response to their environment

3. Lamarck (continued) • Hypothesis tried to explain: • A. The fossil record showed that organisms in the past were different from those alive today • B. Each organism seemed well adapted to its environment

4. Lamarck (continued) • Lamarck suggested that acquired characteristics explains how evolution occurs: • Acquired characteristics-traits an organism develops during its lifetime • Lamarck thought organisms recognize the need to acquire a trait • Ex: antelopes understand the need to run fast; swimming birds understand the need to have webbed feet; wading birds understand the need to have long legs

5. Lamarck (continued) • Lamarck thought that by using particular body parts organisms could develop the required characteristics. • Ex. The long neck of a giraffe • Lamarck thought the acquired characteristics would be passed on to offspring which changes the population from one generation to the next.

7. Charles Darwin and Natural Selection • Charles Darwin supported evolution • 50 years after Lamarck • Published “Origin of Species by Means of Natural Selection” • Traveled around the world on the British ship HMS Beagle—studied many organisms in the Galapagos Islands.

8. Darwin’s Observations • No 2 individuals in a population are exactly alike. • Organisms vary in size, color, behavior—variation, no acquired characteristics are inherited. • Individuals with traits better adapted to their environment have a greater chance to survive and pass on their traits to offspring • This process is called “Natural Selection”

9. Darwin—Natural Selection • Natural Selection (“Survival of the Fittest”)—those best adapted will survive. • 1. In any population, more offspring are produced than will survive and reproduce. • 2. There is competition for resources (space, food, mates) among offspring • 3. There is variation of traits within populations of organisms

10. Natural Selection--continued • 4. Some of these traits are more advantageous than others. • 5. Because organisms with adaptive traits have a greater chance of reproducing, their offspring tend to make up an increasingly larger portion of the population.

11. Show Camo PPT pictures…

13. Which population will most likely survive through major environmental changes? BIODIVERSITY!!!

15. Darwin’s finches each have different beak shape and size. • What does this tell us about them?

17. Natural Selection At Work • 1850’s in England, most peppered moths were light, speckled color • When they landed on light colored tree trunks, they blended • Since predators (birds) could not see them, they ate the dark colored moths (they were easier to see). • Early 1900’s—industrial air pollution covered tree trunks with soot, making the light moths easier to see • birds started to eat more light colored moths

18. Natural Selection At Work--continued • Pollution control has resulted in trees having light colored trunks • light colored moths are becoming more common again.

19. Lamarck vs. Darwin • Similarities • 1. Observed a wide diversity of life forms that are adapted to their environments. • 2. Proposed that species evolve gradually over time.

20. Lamarck vs. Darwin (continued) • Differences • 1. Lamarck-acquired characteristics-the environment produces needs which result in organisms directing their own adaptations. • 2. Darwin-Natural selection-random variation was already present and natural selection produces adaptation.

21. How does the following video demonstrate natural selection? • CLICK ME