Download Unit 5- Evolution Write your definition of Evolution. Scientist`s

Unit 5- Evolution
Write your definition of Evolution.
Scientist’s Comments What is Evolution?
• Common descent
• Organisms are descended from a common
ancestor.
• All organisms are related to a common
ancestor.
• Common descent of living forms
• With common descent things change
common ancestor and that more complex
forms of life descended from less complex
forms.
4. Jean-Baptiste Lamarck – Proposed that
changes in the environment caused an
organism’s behavior to change and that these
changes would pass on to their offspring. He
called this the inheritance of acquired
characteristics.
Early views of earth
• Before Darwin, it was believed that the earth
and its environment was the same now as in
the beginning.
• Change over time
• Evolution is the change in various
characteristics of organisms
• Read pages 298 – 301 in your Biology Textbook
• What beliefs influenced men’s opinions of the origin
of life on earth before Darwin came up with his Theory
of Evolution?
• What 4 scientists made contributions to our
knowledge of evolution before Darwin?
• What theory of geologic change set the stage for
Darwin’s theory?
Early Ideas Before The Theory of Evolution: Early Views
• Man’s early views were influenced by
teachings from the Bible.
• The Age of the Earth was a key issue in early
debates concerning evolution.
• The age of the earth was believed to be 6,000
years.
Darwin was not the first person to come up with ideas
about evolution. Four scientists in particular were
important:
1. Carolus Linnaeus – Proposed that plants
changed through hybridization.
2. Georges Leclerc – Proposed that species
shared ancestors. Also rejected the idea that
the earth was only 6000 years old.
3. Erasmus Darwin – Darwin’s grandfather
Proposed that all living things descended from a
• Man’s views of early earth was based upon 3
concepts:
1. Theory of Catastrophism –Natural
catastrophic events such as
volcanoes, floods and earthquakes
were responsible for mass
extinctions.
2. Gradualism – –Changes on earth
occurred by small steps over a long
period of time.
3. Uniformitarianism – Rock strata
( layers ) demonstrate that geologic
processes add up over long periods of
time to cause great changes in the
earth’s crust.
Pre-learning questions….
What does evolution mean?
A) When a monkey changes into a human
B) Caterpillar changes to a butterfly
C) Change in a species over time
D) When bacteria turn into viruses
Video Questions Origins of Earth
• Answer these questions after reading the textbook
pages 368-371
1. Describe the scientific explanation for the
origin of earth.
•2. Describe the conditions present during the
time earth was forming.
Evolution
Evolution -A change in species over time
Father of Evolution -Charles Darwin
-traveled to Galapagos Islands in 1800s to study
plants & animals
-He observed unique species and interesting
changes in their structure
STOP THINK AND REVIEW…
Name one organism that Darwin saw in the Galapagos
that had never been seen before
Examine the pictures in the slide presentation
1) What do you see?
2) What is this an example of?
3) How might the appearance of this insect help
it to survive?
How did Darwin justify his Theory of Evolution?
• Darwin began his voyage thinking that species
could not change.
• He knew that man had “forced” change
through artificial selection or what we call
selective breeding.
b) Sea iguanas
Darwin said nature “selected” those organisms who
would survive to reproduce and make offspring better
suited to survive their environments. This was how
Darwin proposed that organisms evolve.
c) Turtles
Natural Selection
a) Peacocks
d) Duck billed platypus
Darwin’s Book -Data gathered from journey led him to
write a book in 1859 -“Origin of Species By Means of
Natural Selection”-most famous science book ever
written -it was extremely controversial because it was
proposing the idea that species evolve, which
contradicted the Bible
Scopes Trial
• In 1925, a school teacher – John Scopes was
prosecuted for teaching Darwin’s theory of evolution to
his students
• Nick named “The Monkey Trial” • William
Jennings Bryan vs Clarence Darrow
• Scopes lost and was found guilty. Ordered to
pay $100 fine.
• Organisms well suited to their environment
survive longer and reproduce in greater
numbers than those less suited. In other
words…
• Individuals that have inherited beneficial
adaptations produce more offspring on average
that other individuals.
Which of the following would be an example of an
organism being well suited to its environment?
a) Bird with wings that can’t fly
b) Lizard blending in with the leaves
c) Brightly colored moth on a tree
d) Animals with extra fur in the summer
• 5 Factors that make Natural Selection Work
STOP THINK AND REVIEW…
1. Variation- all species have genetic differences
What made Darwin’s book so controversial?
2. Struggle for Existence -All species compete
for survival
a) It proposed that organisms change over time
b) It went against the common belief in God
and creationism
c) It contradicted the Bible
d) All of these
3. Only some survive -some survive life’s
challenges better than others
4. Genetic change -offspring are the result of
successful parents.
5. Adaptation- some organisms can make
changes to be bette suited to their
environment. Ex: camouflage, thicker fur,
burrowing in the desert
Evidences of Evolution
• Fossil Records - Preserved or mineralized
remains or imprint of an organism that lived
long ago. (formed by time, heat, pressure)
• Fossils show change in body structure over
time.
Vestigial Structures
-Organs that no longer serve a useful purpose
or function.
-EX: Wisdom Teeth, Tail bone Pelvic bone in
Whale
Homologous Structures
The more similar an organisms _____, the more closely
they are related.
a) DNA
b) Limbs
c) Bones
d) Head structure
A structure that no longer serves a useful purpose or
function is called:
a) Homologous
b) Fossil
c) Vestigial
d) Embryonic
An example of a structure that no longer serves a
purpose would be:
• Parts that are similar in structure – show
possible common ancestry
a) Tailbone
• EX: arm of human, wing of a bird, fin of a
dolphin
c) Pelvic bone on a whale
b) Wisdom teeth
d) All of these
DNA Similarity
• Scientists look at DNA to see evolutionary
relationships (similarities)
Homologous structures (parts that are similar in
structure but different in function) may show…
a) Incorrect fossil records
• More similar the DNA, the more closely they
are related
Embryo Studies
-embryos with similarities show possible
common ancestry
-EX: humans, chickens, fish all have gill slits &
tails
b) 2 organisms may have come from a common
ancestor
c) Similar function in organisms
d) That organisms are unrelated
Left Side Output Create a “Tree Map” Evidence for
Evolution
STOP THINK AND REVIEW
Draw a picture to represent each one
Scientist can analyze these to see how body structures
have changed over time:
Other Mechanisms of Evolution Translation: What are
some other causes of Evolution?
A) Vestigial structures
B) Homologous structures
C) Fossils
D) Limb structure
1. Gene Flow
• the movement of alleles between
populations.
• occurs when individuals join new
populations and reproduce.
• keeps neighboring populations
similar.
• Low gene flow increases the chance
that two populations will evolve into
different species.
2. Gene Drift
• a change in allele frequencies due to
chance.
• causes a loss of genetic diversity.
• most common in small populations.
• Causes of Genetic Drift
• A population bottleneck event. –
occurs when an event drastically
reduces population size.
• The founding of a small population –
occurs when a few individuals start a
new population –
Genetic drift has negative effects on a population
•
•
less likely to have some individuals that
can adapt
harmful alleles can become more
common due to chance
3. Sexual Selection
• What would you use to measure the changes
if they were taking place?
The Hardy-Weinberg Model
• 2 scientists ( Hardy & Weinberg ) developed
an ideal model to use to compare with any
population.
• Their model showed that:
1. genotype frequencies ( how often a
trait occurs ) in a population stay
the same over time as long as
certain conditions are met.
2. Future genotypic frequencies could
be predicted.
• The model identified the 5 conditions needed for a
population to remain at equilibrium.( to stay the same )
• HWB Criteria
• It must be a large population
• It must be a large population
• No immigration or emigration
• No mutations
• Must have Random Mating –( no
sexual selection )
• No Natural Selection occurring
Summation of Evolution
Summation of Evolution
• occurs when certain traits increase
mating success.
• There are 5 factors that lead to evolution…
• occurs due to higher cost of
reproduction for females.
1. Genetic Drift
Changing gene frequencies due to
chance.
2. Gene Flow
Two types of sexual selection.
–intrasexual selection: competition among
males
–intersexual selection: males display certain
traits to females
Hardy-Weinberg Equilibrium
Think about it…
• If you were studying a population of animals
to see if they were evolving…
• How would you know how they were
changing?
Movement of alleles from one
population to another.
3. Mutation
New alleles form due to mutations in
the DNA.
4. Sexual Selection
Certain traits may improve mating
success.
5. Natural Selection
Certain traits may be an advantage for
survival.