Download Chapter 16

Chapter 16
Darwinian Evolution
What is evolution?
A theory that states species slowly change
over time through the process of natural
selection.
What is a theory?
A hypothesis that is supported with a lot of
scientific evidence.
Who was Charles Darwin?
1.
British
2.
Lived in the 1800s
- born on same day as Abe Lincoln
3.
Born into a reasonably wealthy family
- dad was a doctor & very overbearing
4.
Originally went to college to be a doctor, but
didn’t like the blood & screaming of 19th
century surgery (no anesthesia)
5.
Dad forced Charles to become a minister, but
Darwin really wanted to be a naturalist
- he continued to study nature on the side
while in theology school
6.
When Charles graduated, he took a job as a
naturalist on the H.M.S. Beagle which was
taking a 5-year voyage around the world.
- Dad was not happy
Darwin’s Journey on the Beagle:
Darwin’s Journey on the Beagle:
1. Charles was a good scientist
- he collected lots of specimens
- he wrote down a lot of notes
2.
3.
4.
What 3 patterns of biodiversity did Darwin observe on his voyage?
Species Varied Globally
Different, yet ecologically similar, animal species
inhabited separated, but ecologically similar
habitats. He wondered, how this could happen?
Species Varied Locally
Different, yet related, animal species often
occupied different habitats within a local area.
Species Varied Over Time
Some fossils of extinct species were similar to
living species.
The Galapagos Islands
- Located 500 miles off the coast of South America near the equator
- Each island has different climates & habitats
- Darwin noticed that similar species on different islands had special
adaptations to survive in those habitats
- His studies of their finches & tortoises impacted him greatly
Based on observations made on this trip, Darwin came up with his theory of
evolution by natural selection
1.
Bishop Ussher (1581-1656)
- using the Book of
Genesis, he calculated
that the universe was
created on October 23,
4004 B.C.
- later theologians
calculated that this
began at 9:00 am London
time; midnight Garden of
Eden time
- in Darwin’s day, most
Europeans believed this.
2.
James Hutton & Charles Lyell
- Both were geologists
- Hutton stated that the Earth is much older
than Ussher believed (deep time), and that
there were different processes that shaped the
earth as we know it.
- Lyell stated that the phenomena that shaped
the world millions of years ago continue to
occur today. He also stated that the laws of
nature are constant & that we must explain
past events through observations made in the
present. Lyell called this concept
uniformitarianism.
- Darwin felt that if geology could change like
this, life could too.
3.
Jean Baptist-Lamarck
- French naturalist
- proposed a theory of evolution
- His mechanism was wrong:
A. Tendency towards perfection
- organisms are continually
changing that help them live better
B. Selective use & disuse
- this is what allows the organism to
change
C. Inheritance of acquired traits
- a body builder could pass on his big
muscles to his son
4.
Thomas Malthus (1766-1834)
- English economist
- In a 1798 essay, he stated
that if the human
population continues to grow
unchecked, we will eventually
run out of resources.
- Darwin recognized that this
would be even more true in
nature because nature
produces more young and
resources are even more
limited.
What is a theory?
A hypothesis with lots of empirical (scientific)
evidence. It may also be to as a statement that
unifies many related hypotheses into a single
statement.
What is evolution?
1. Change in the genetic makeup of a species over
time
2. This can lead to the creation of a new species
1.
2.
3.
Why did Darwin wait 23 years to present
his idea?
It challenged fundamental scientific
beliefs.
As a trained theologian, he was stunned &
disturbed by them.
He knew it would create a firestorm of
opposition.
What prompted Darwin to publish his idea?
1. He received a letter from a fellow scientist named
Alfred Wallace.
2.
Wallace was proposing a similar hypothesis.
3.
Darwin wanted to make sure he would get the
proper credit for his work.
What is the name of Darwin’s famous book?
Origin of Species by Means of Natural Selection
- Origin of Species for short
- published in 1859 (151 years ago)
- 1st printing sold out in the first day
- current Amazon.com rank:
2300/420000+ (inside the top 1% in sales)
What is inherited variation?
The natural variation of phenotypes within a
population.
What is artificial selection?
1.
Humans choose which of the natural variations
are to be passed on to the next generations.
2.
These traits may not actually improve fitness.
(Fitness = survive & reproduce)
Evolution by Natural Selection:
1.
Struggle for Existence
- high birth rates &
limited resources
lead to competition
- this concept shows
the influence of
Malthus
Evolution by Natural Selection:
2.
Survival of the Fittest – those with the best
adaptations survive &
reproduce
Fitness – ability to survive & reproduce
Adaptation – inherited characteristic that increases
fitness
Adaptations can be:
A. Anatomical/Structural
B. Physiological (life’s chemical processes)
C. Behavioral
What is the relationship between adaptations &
fitness?
Adaptations increase fitness
Evolution by Natural Selection:
3. Descent with Modification
A. Natural selection, over time,
produces organisms that have
different structures, occupy
different niches, & live in
different habitats.
B. Implies that all organisms are
related to each other because
they inherited the
adaptations from their ancestors.
Evolution by Natural Selection:
4.
Common Descent
- All species arose from a common
ancestor.
- a.k.a. the “Tree of Life”
1.
The Fossil Record
- Fossils show the
transitions of
species during
evolution
2.
Similarity in Anatomy – related species
have similar anatomy
Man-Gorilla-Chimpanzee-Orangutan-Gibbon
2.
Similarity in Anatomy continued:
What is a homologous structure?
A. Developed from the same
embryonic tissue.
B. Created by divergent
evolution.
* The only way that this could happen is that the
species must be related.
2.
Similarities in anatomy continued:
What are analogous structures?
A. Similar structures that don’t come from
the
same embryonic tissue.
B. Created by convergent evolution.
C. Similar habitat created the evolutionary
pressure that led to the similar structures.
* For example, the analogous structures of
sharks & dolphins suggests that they are not
closely related.
2.
Similarities in anatomy continued:
What are vestigial organs/structures?
A. Homologous structures that are small
unused.
B. They are evolutionary leftovers &
they give a hint to what the common
ancestor was like.
&
3. Similarities in
Embryology
Closely related species share
common embryology.
4.
Similarities in DNA bases
sequences & amino acid
sequences
more similarities = closely related
* diverged from common ancestor
more recently
fewer similarities = less closely related
* diverged from common ancestor
a long, long time ago
H = Human
C = Chimp
The DNA of chimps and
humans is 98.4% identical.