Evolution

Evidence shows that living things have changed over time.

Evolution is the change in hereditary features of a speciesover time.

Although many scientists have studied evolution, there are two that we will study.

This is Jean Lamarck, a Frenchscientist from the early 1800’s.

He developed the first theoryof evolution.

Lamarck’s theory is based on acquired characteristics.

Lamarck’s theory is often summarizes using giraffes.

For example,

All giraffes once had short necks. They ate all of the lower leaves on the trees and had to stretch their necks to reach the higher leaves.They passed this “acquired trait” on to their offspring, and now all giraffes have long necks.

Sounds simple, right? But does it make sense. At least one man did not think so.

Enter Charles Darwin, an English scientist from the mid-1800’s.

His theory of evolution is still used today.

His theory is based on natural selection, which states that organismsthat are better suited to their environments will survive. (“survivalof the fittest” )

How would Darwin explain why all giraffes have long necks?

Darwin would say that at one time, there were some giraffes with

long necks and some with short necks. The long-necked giraffes

were the ones that could reach more food, so they had a better

chance of surviving and passing the long-necked trait on to their

offspring.

Factors that control Natural Selection -

1. Organisms produce more offspring than can survive.

2. There is variation among individuals of a species.

3. Some variations help an organism to survive and reproduce.

4. Over time, offspring with more helpful variations make up more and more of the population.

Darwin published his theories in a book called

On the Origin of Species by Means of Natural Selection in 1859.

Variation - appearance of an inherited trait that makes an individual different than other of the same species

If enough variations occur, a new species could arise.

Adaptation - a variation that makes an organism better suitedTo its environment; caused by migration, isolation, mutations, etc.

Other evidence for evolution:

1. Homologous structures - body parts similar in origin andstructure; evidence of common ancestor

2. Vestigal structures - no longer used, but may havehad a purpose in the past; ex - tailbone, appendix

3. Embryology - study of similarities in embryos fromdifferent species

4. DNA - can study and compare DNA to see howclosely organisms are related

Ex. -dogs and bears are each other’s closes relatives

Primate Evolution

Monkeys, apes and humans are all primates. We all share:

1. Opposable thumbs2. Binocular vision3. Flexible shoulders4. Similar proteins (hemoglobin)

Hominids - human-like primates; walked upright; ex. Lucy(Ausralopithicus-3 million yrs. Old)

“Evolution of Man”

Homo habilis “handy man” - lived 1.5-2 million years ago

Homo erectus “upright man” - lived 1 million years ago

Homo sapiens “wise man” - 300,000 years ago

Early Homo sapiens included to diverse branches:

1. Neanderthals

2. Cro-magnons

Not really closely related