Transcript CB-Evolution

Evolution
I.
Origins of Life on Earth
A. Oparin Model of Life
1. In 1924, Russian scientist Aleksander
Oparin proposed that Earth is
approximately 4-5 billion years old and
that the ancient atmosphere contained:
a.
b.
c.
d.
ammonia (NH3)
water (H2O) vapor
methane (CH4)
hydrogen (H2)
 Which important gas(es) is/are
missing?
2. Energy from the sun, lightning and heat from
the earth broke apart these molecules.
3. The atoms randomly bonded together to form
amino acids, sugars and fatty acids, which
accumulated in the oceans.
 What are proteins made of?
4. Over millions of years these organic
compounds combined to form simple cells that
filled the Earth’s primordial oceans.
B.
Miller & Urey’s Experiment
1. In 1953, Stanley Miller and Harold Urey
showed that you can make organic
compounds from inorganic molecules.
2. The experiment:
a. Miller electrocuted a mixture of water vapor,
methane, ammonia and hydrogen gas.
b. He collected the liquid and found amino
acids, simple sugars and simple fats!
c. However, as of today, no one has produced
a living cell from nonliving materials.
Miller & Urey’s Experiment (1953)
II. General Info
A. Evolution means “change over time”
B. Process by which modern organisms have
descended from Earth’s earliest forms of life
C. It is a scientific theory
 What is a scientific theory?
 It is a well-supported, testable explanation
of events that occur in the natural world
Just a Theory? Movie
D. Foundation of modern biology that unifies many
different branches of science
III.
Darwin’s Theory of Evolution
A. Background Info
1. Most Europeans in the 1700-1800’s
believed:
a. Earth was only several thousand years old
b. Since their creation, neither plants nor
animals had changed
 Approximately how old is Earth?
B. Ideas that Shaped Darwin’s Thinking
1. In 1795, James Hutton proposed that layers
of rock form over millions of years; therefore
Earth had to be more a few 1000 years old
2. In 1841, Thomas Malthus predicted in his
Essay on the Principle of Population that the
human population will grow faster than the
space and food needed to sustain it
 What happens to populations of
organisms that exceed their resource limits?
3. Hypothesis of Acquired Traits
a. In 1809, Jean Baptiste de Lamarck proposed
that traits developed during a parent’s
lifetime are inherited by their offspring
 Is this a supported hypothesis?
My, How You’ve Changed!
Prior to the 1800s, life scientists knew
that living things changed over
generations. They just didn’t know how
these changes were brought about.
1. Make two columns:
Inherited Traits
Acquired Traits
2. 1st column, list the traits that you believe you have
always had. Ex: brown eyes, curly hair
3. 2nd column, list your acquired traits.
Ex: playing a musical instrument
4. Which of the items in your lists do you think you
might pass on to your children?
4. In 1830, Charles Lyell explained in his book
Principles of Geology how geological events
(volcanoes, earthquakes) build up or tear down
the Earth over millions of years
a) Explains how marine fossils can end up on
mountain tops
C. Evolution by Natural Selection
1. Voyage Around the World
a. In 1831, Charles Darwin set sail from England on
the HMS Beagle for a voyage around the world
Voyage of the HMS Beagle
b. As the ship’s naturalist, Darwin recorded
observations and collected specimens of the
many plant and animals species he saw
c. Galapagos Islands
i.
ii.
Group of islands 1,000 km off the coast of Central and
S. America that are close together but have very
different climates and an amazing variety of species
(iguanas, finches, tortoises)
Diverse animals and plants seemed very well suited to
their island’s environment
iii. Beak shape of each species of Galapagos finch is
related to its eating habit
iv. Based on his observations, Darwin hypothesized that
the Galapagos plant and animal species evolved
from ancestors from Central and S. America
2.
On the Origin of Species (book)
a. 1859, Darwin published his findings
b. Species are not perfect and unchanging
c. Proposed a mechanism for evolution called
natural selection

organisms with traits best suited to their
environment are more likely to survive and
reproduce (“survival of the fittest”)
d. Survival of the fittest
i. Fitness = ability of an organism to survive
and reproduce in its environment
ii. Adaptation = inherited characteristic that
increases the chance of survival (write
examples)
iii. Over time, natural selection results in
changes in the inherited traits of a
population, increasing that species’
fitness.
Natural Selection Movie
3. Summary of Darwin’s Theory
a. Organisms produce more offspring that can
survive (think mice, bunnies, etc)
b. Individual organisms of the same species
differ, and some of this variation is
inheritable.
Homo sapiens
Drosophila polymorpha
i.
Today, we know these variations are the result of
mutations.
ii. Mutations occur by random chance and if favorable, it
will be inherited by organism’s offspring (e.g. Peppered
moths, antibiotic resistant bacteria or insecticide resistant
insects)
c.
Organisms struggle to survive
 Why?
i. Individuals of each species compete for resources
(food, space, mate, etc)
d. Species alive today have descended with
modification from ancestral species of the past. This
process unites all organisms on earth into a single tree
of life.
A.
IV. Evidence for
evolution
The Fossil Record – provides evidence about the
history of life on Earth
1. Fossils are preserved impressions or physical
remains of an organism that once lived.
Petrification
Impression
Cast/Mold
Amber
Cast/Molds
Baby mammoth
found frozen in
Russia in 2007
Iceman found
frozen in the
Alps, Italy in
1991
2. Fossils occur in a particular order; simpler forms
existed before more complex forms (e.g. the
oldest known fossils are prokaryotes)
3. Fossil dating techniques
a. Relative Dating - layering of sediment results
in the oldest and simplest fossils usually
further down
b. Absolute/Radiometric Dating
i.
Some rocks contain elements that are
radioactive and will decay (break down) at a
constant rate over time
ii. Half-life = length of time required for half of
the radioactive atoms in a sample to decay
iii. Scientists can calculate the age of a sample
by measuring remaining amount of
radioactive isotopes like carbon14
4. Transitional Forms
a. Intermediate forms of life appearing in the fossil
record that are "in-between" existing types of
organisms found today or in the past
b. Many examples of transitional forms exist in the
fossil record
The Aetiocetus nostril placement is an intermediate form
between the ancestral form Pakicetus and the modern
beluga.
Evolution of
Horse Feet
 sampling of horse
fossils leading to modern
horses
 the diagram shows
transitional stages
whereby the four-toed
foot became the singletoed foot of Equus
 shows the reduction of
toes through time
Archaeoptryx
A model of Tiktaalik
roseae, a fish in transition
to becoming a land
animal.
Early transitional form
between fish and
amphibians.
Limb Evolution
How do we know
evolution happens?
MOVIE
B. Biogeography
1. Geographical distribution of species
2. Species living on different continents who descended
from the same ancestor, look slightly different because
they were exposed to different ecological conditions
(e.g. armadillos and anteaters, lions and tigers)
3. Consistent with plate tectonics
C. Comparative Anatomy
1. Homologous structures – made of the same
types of bones, but the function or structure
may be different
a. Example: basic bones in the arms of a
human, wings of a bird and fins of a whale.
2. Vestigial Structuresinternal structures that
serve no known
purpose.
3. Atavism - rare reappearance of a lost
characteristic specific to an evolutionary
ancestor (gene is turned back on)
a. Ex: whales with legs, human babies with true tails
The hind-flippers of
a bottlenose
dolphin found in
Japanese coastal
waters in 2006.
Yellow arrows
indicate the location
of a well-formed
atavistic set of hind
limbs.
(photos from the
Taiji Whaling
D. Comparative Embryology- closely related
organisms pass through similar stages as
embryos -> shows common ancestry
E. DNA
1. Scientists can compare the DNA of different
species to determine their relatedness
2. Closer similarities means more likely to have a
common ancestor
3. Example: a human’s DNA is ~ 97% similar to that
of a chimpanzee.
Genetic relatedness
Number of amino
acid differences
in hemoglobin