Download Evolution – Just A Theory?

Evolution – Just A Theory?
The Selfish Gene by Richard
Dawkins
Quic k Ti me™ and a
T IFF (Unc om pres s ed) dec om pres s or
are needed to s ee t his pic t ure.
What did you think of the reading?
 Answer the questions in class…
 How can we make connections between this
reading and our previous units?
 Why would the idea of sexual reproduction
be important for evolution?

Whose the man?
 Charles Darwin
 Born 1809, 5th son
of wealthy physician

Studied medicine
and natural history
in Edinburgh

Studied to be a
clergyman at
Cambridge
Charles Darwin’s Theory

Charles Darwin – 19th century scientist

Famous for Theory of Natural Selection
– In a population, naturally occurring
variations affect which individuals
survive and reproduce
– Natural selection - the force which acts
on populations, and the best adapted
organisms survive
– Evolution - the process by which
populations change over time
What is all this controversy?

150 years of controversy
Competing Beliefs
Many people, even today, do not believe in the
theory of evolution, but instead, the idea of
creationism.
 Creationism is static and unchanging… but has
meaning and purpose.

Intelligent Design
Defined as "certain features of the
universe and of living things are best
explained by an intelligent cause, not an
undirected process such as natural
selection.”
 A “creator” was responsible for the design
of what exists on earth
 NOT a scientific theory/proposal due to
the “fact” that there is a lack of evidence
and should NOT be taught in science
classrooms!

The Theory of Evolution

The term theory in colloquial use is closer to the
concept of a “hypothesis” in science (an educated guess
or hunch).

In science, a theory  hypothesis. A Theory is more
comprehensive than a hypothesis.

National Academy of Science:
“a well-substantiated explanation of some aspect of
the natural world that can incorporate facts, laws,
inferences, and tested hypotheses.”
Evolution in the news
1925: Scopes “Monkey” Trial
– science teacher charged with contravening
Tennessee’s Butler Act, which forbade the
teaching of "any theory that denies the story
of the Divine Creation of man as taught in the
Bible, and to teach instead that man has
descended from a lower order of animals."
 1980s: Alabama and Louisiana laws mandating
teaching of “creation science” found to be
unconstitutional
 Right now: Challenges to teaching of evolutionary
theory versus “Intelligent Design” in Kansas,
Michigan, Pennsylvania

Evolution in (some) schools…

Disclaimer put into biology textbooks in
Georgia- this is now found to be
unconstitutional!
Darwin’s Theory


Darwin published his findings from his trip around
the southern hemisphere in a book called On the
Origin of Species
– Darwin visited the Galapagos Islands, a group of
very small islands off the coast of Ecuador.
– Even though the islands are close together,
each island has a unique climate.
Darwin proposed that evolution worked by way of
natural selection.
Voyage of the Beagle

1831: Joined the HMS Beagle on five year voyage
to South America
– Studied geology, paleontology, plants and
animals
Animals of the Galapagos
• Darwin could tell by the shape of the Giant
Tortoises’ shells and their neck length
which island they were from.
Darwin’s Theory
1.
Organisms differ, and some of this variation is
heritable.
– Some cows produce more milk, some apple
trees produce larger apples, etc.
–
People now use artificial selection: nature
provides the variation, but humans select for
the variations they find useful
• Ex. Only breed the dogs that lose the least
amount of fur.
Darwin’s Theory
2. Organisms produce more
offspring than can survive, and
many that do survive do not
reproduce.
Does Darwin’s 2nd part still apply to humans?

Many
countries are
prime
examples of
overpopulation
Darwin’s Theory
Because more organisms are
produced than can survive, they
compete for limited resources.
– Struggle for existence.
– In this struggle, predators that are
faster get more prey.
Darwin’s Theory
4. Natural selection causes species to
change over time.
– Survival of the fittest!!! (natural
selection)
– Adaptation is any inherited
characteristic that increases an
organism’s chance for survivial.
– Those individuals best adapted to their
environment will survive and reproduce.
Darwin’s Theory
5. Species alive today are descended with modification from
ancestral species that lived in the distant past.
All living organisms are
Related to one anothercommon descent.
 Single “tree of life” links
all living things (classification)
