Chapter 15 Darwin’s Theory of Evolution. Charles Darwin Born February 12, 1809 – Died April 19,...
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Transcript of Chapter 15 Darwin’s Theory of Evolution. Charles Darwin Born February 12, 1809 – Died April 19,...
Chapter 15
Darwin’s Theory of Evolution
Charles Darwin Born February 12, 1809
– Died April 19, 1882 English Naturalist Sailed the world in 1831
on a 5 year voyage aboard the H.M.S. Beagle
Galapagos Islands!!!! Began the modern
perspective on the theory of evolution
Origin of Species (1859)
The Descent of Man (1871)
15-1 The Puzzle of Life’s Diversity
Charles Darwin collected over 3,000 different species of plants and animals
The species varied per island Insects, reptiles and birds were the most
influential to Darwin Many species showed evolutionary diversity
varying from fossil records Provided evidence which would forever
change Biology
“I have called this principle, by whicheach slight variation, if useful, is preserved, by the term Natural Selection.”
—Charles Darwin from "The Origin of Species"
Monkeys to Man?
The Descent of Man challenges the scientific community to believe man has evolved from a preexisting form, primates.
Like other species, man has evolved from primitive unicellular organisms through primates to what we now recognize as humans beings, Homo sapiens.
What does Darwin mean?
In the random shuffle of heredity, all organism’s of the same species are born slightly different.
This slight difference gives them the “edge” to survive
The cruelty of nature challenges species’ to struggle for survival
Nature selects the “better” organism to survive
Darwin’s theory of Natural Selection was born
15-2
Ideas That Shaped Darwin’s Thinking
Hutton and Lyell:
(1700’s) James Hutton & Charles Lyell first suggested the Earth was changing over time.
Recognized the Earth was millions of years old.
They believed the same “Earth changing processes” were always in effect.
1795 James Hutton published his theory of geological forces which changed Earth.
Proposed the Earth was more than a few thousand years old.
Charles Lyell published Principles of Geology. Theorized that processes occurring now have
shaped the Earth’s geological features over very long periods of time.
BOTH Hutton and Lyell influenced the way Darwin thought about the ever changing Earth.
Jean-Baptiste Lamarck
One of the first to recognize that living organisms changed over time.
1809, Lamarck published his theory on how organisms changed.
He proposed that by selective use or disuse of organs, organisms lost or gained certain traits during their lifetime. Over time, the changes led to a change in an entire species.
Proposed all organisms wanted their species to be perfect.
Was Lamarck correct?
He was incorrect in several ways. An organism’s behavior has no effect on its
inheritable characteristics. YOU have NO control over the traits you
inherit. Lamarck was one of the first to develop a
scientific theory of evolution.
Thomas Malthus
1798, an English economist named Thomas Malthus realized that people were being born faster than they were dying.
He realized that limiting factors were a major concern for population growths
He theorized that war, famine and disease limited the growth of the human population.
15-3
Darwin Presents His Case
Natural Variation and Artificial Selection
Darwin argued popular belief by stating that natural variation was found in all types of organisms
Natural variation is the differences found among individuals of the same species
For example, zebra stripes milk production in cows
Through artificial selection breeders can alter natural variation
With artificial selection, humans interfere with the natural process to select the “best.”
Humans select the naturally occurring variation
Natural Selection
Darwin believed in the process of natural selection results in changes of a species over time to better adapt to their environment.
He referred to this as the survival of the fittest, individuals more suited to their environment will survive and reproduce more successfully.
He believed fitness was a result of adaptations. Also believed that a species must overcome a
struggle for existence by obtaining food, living space, and other life necessities like shelter.
Ancestors?
Darwin proposed that all species had ancestors He referred to this as descent with modification Each species had descended with change over time Darwin theorized that if we looked back far enough,
we could find evidence of a common ancestor among all species.
Known as common descent In early stages, chickens, turtles and rats look similar
providing they shared a common ancestor These are known as homologous structures