Darwin vs. Lamarck

Lamarck Darwin

Jean-Baptiste LaMarck French, Early 1800’s Theory of Inheritance of Acquired Characteristics Two main points…

1. Principle of Use & Disuse: Most used body structures develop, unused structures waste away 2. Inheritance of Acquired Characteristics: Once the structure is modified, the new trait can be inherited (passed to offspring)

Explain the picture below as if you were LaMarck…

Why we don’t believe him… Genetics : Gregor Mendel discovered that traits are passed down through GENES (which aren’t affected by the outside world in that way) Experiments: show that changes that occur in an animal’s life are not passed on to its offspring

Charles Darwin “The Father of Evolution” sailed on the HMS Beagle to the Galapagos Islands. Studied many species of finches. Published book in 1845: “On the Origin of Species by Natural Selection”

Darwin’s Theory of Evolution (don’t copy all this it’s on your handout) “Survival of the Fittest” “Natural Selection”

Natural Selection Process by which favorable heritable traits become more common in successive generations of a population of reproducing organisms, and unfavorable heritable traits become less common.

Natural Selection

Four main points… 1. More organisms are produced than can survive…leads to COMPETITION OVER RESOURCES Ex’s of resources…  Water  Food  Habitat  Mates

2. Individuals within a population vary, and some of these traits are heritable.

3. Some variations are FAVORABLE (increase chances for survival/ reproduction) Male vs. Female Cardinals Male color attracts female= reproductive advantage

4.Better adapted individuals survive and reproduce These are the individuals that will pass on their genes to the next generation. This can change the GENE POOL: Includes all the genes of every reproductive member of a population

What The theory of evolution IS NOT!!! It does NOT occur in INDIVIDUALS…only populations! It does NOT happen quickly…the Earth has a Looooooong history! It does NOT explain how life came to be on Earth, just how it evolved after it was here. It does NOT have any driving force except the competition for limited resources.

Darwin’s Finches…p 558 Illustrate SPECIATION: when a species breaks into two (or more) The organisms in the two species can no longer… INTERBREED What could cause this to happen? Geographic barriers Occupy a new niche/habitat Reproductive Isolation-

Natural selection

What would Darwin say to explain why giraffe’s have such long necks? See pg. 553

Types of Natural Selection Stabilizing Selection Occurs when natural selection works against the 2 extremes of a trait to make the population more uniform.

Stabilizing Selection

Birth weight of babies Babies that are too big or too small might have less chance of being born healthy.

Natural Selection Directional Selection Selects the extreme of 1 trait.

Directional Selection In a population of plants, flowers with the brightest color might be selected for in order to attract the most pollinators.

Natural Selection Disruptive Selection Selects against the mean of the population.

Disruptive Selection If there are 2 types of seeds to eat for a population of birds, either of 2 different beak shapes (sharp or blunt) might be selected for, but a beak that’s the average of the 2 shapes might not be particularly good at eating either seed, so it would be selected against.

2 types of Evolution

Evolution Types Convergent Evolution Acquiring the same biological trait in unrelated lineages These traits may be a result of occupying similar environments.

Convergent Evolution

Evolution Types Divergent Evolution The accumulation of differences between groups which can lead to the formation of new species, usually a result of different groups of the same species adapting to different environments, leading to natural selection defining the success of specific mutations.

Divergent Evolution

Evolution- “Change Over Time” All of the changes that have occurred in living things since the beginning of life on Earth

History of the Earth 4.5 bya Earth forms 3.5 bya 1 st PROKARYOTES 2.1 bya 1 st EUKARYOTES

700 million years ago…

Evolution occurs over MANY generations Evolution occurs within POPULATIONS (NOT individuals) Evolution involves genetic changes in a SPECIES (Members of a species interbreed to produce healthy, fertile offspring)