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Evolution
Evidence shows that living things have changed over time.
Evolution is the change in hereditary features of a species
over time.
Although many scientists have studied evolution, there are
two that we will study.
This is Jean Lamarck, a French
scientist from the early 1800’s.
He developed the first theory
of 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 organisms
that are better suited to their environments will survive. (“survival
of 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 suited
To its environment; caused by migration, isolation, mutations, etc.
Other evidence for evolution:
1. Homologous structures - body parts similar in origin and
structure; evidence of common ancestor
2. Vestigal structures - no longer used, but may have
had a purpose in the past; ex - tailbone, appendix
3. Embryology - study of similarities in embryos from
different species
4. DNA - can study and compare DNA to see how
closely 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 thumbs
2. Binocular vision
3. Flexible shoulders
4. 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