Transcript Evolution Power Point 2

Intro to Evolution…
Take out a sheet of blank notebook
paper and a pen/pencil!
Introductory Activity…
*You will be working in your rows for this activity.
*I am going to hand a picture to the student at the end of
the row. He or she will copy what they see in 30
seconds.
*When I call time, he or she will pass their own drawing
to the person in front of them.
*The next person will draw what they see from the
student behind them in 30 seconds.
*When I call time, pass it along and repeat the process.
Let’s talk about the activity…
• What happened as the drawings
progressed to the front of the row?
• What theory does this demonstrate?
• What is a theory?
• What are some causes of changes in
the drawing from the original?
The Theory of Evolution –
Change Over Time
EVOLUTION:
the process of change over time
Evolution is the idea that new species
develop from earlier species by
accumulated changes. This is also
referred to as “descent with
modification”.
Evolution is NOT…
It is NOT a fact...it's a theory:
a well supported testable explanation
of something that occurred in the
natural world.
How do these organisms move?
These differences helped Darwin come up with
his theory of evolution.
Jean Baptiste Lamarck
*Use and Disuse Hypothesis (1809)
*Inheritance of Acquired Traits
No longer acceptedBehavior does NOT
affect inheritance.
Lamarck’s Theories
• Tendency Toward Perfection – acquiring features
that help them live more successfully in their
environment
– Ex: birds and flying
• Use and Disuse – Alter size and shape of their
bodies
– Ex: birds transform front limbs to wings
• Inheritance of Acquired Traits – pass on traits to
offspring
– Ex: weight lifter
Evaluation of Lamarck
• Is he on target?
• If not, where did he go wrong?
Charles Darwin
1831 Traveled to the Galapagos Islands
where there was a variety of climates
among the islands
He observed much diversity
in living things and how well
suited they were to their
environments.
Different Land Tortoises on Islands
Hood Island – long neck – sparse vegetation
Isabela Island – short neck – vegetation close to the
ground
Pinta Island – intermediate neck – What could this
say about the environment?
Darwin observed variety within species and also
studied artificial selection
Led him to the theory of evolution by
natural selection
What is natural selection?
Struggle for existence leads to
survival of the fittest
(Natural Selection)
The “fittest” are those with an inherited characteristic
that makes it better suited to survive and reproduce.
These characteristics are called Adaptations.
Adaptations!
Inherited characteristic that increase
an organism’s chance of survival
• Why are most animals in the artic white?
– So they blend in with the snow and avoid being seen!
• Why do sharks have such sharp
teeth?
– It allows them to catch their prey!
• Why do elephants have such big ears?
– To let heat escape their bodies so they can
– stay cool!
Natural Selection results in changes in inherited
characteristics of a population due to the
environment, increasing the species’ fitness in that
environment.
These changes are observed over long periods of time
and many generations.
Natural Selection Make-Believe Scenario
Choose an animal and explain
how its species might evolve over
the next 1000 years as the earth
changes.
Hutton and Lyell
• Studied geology and geological change
• Discovered that the Earth is millions of
years old
• The process that changed Earth in the past
are the same processes that operate in the
present
– Weathering of rock
– Uplifting to form mountain ranges
Lyell’s Influence on Darwin
• If the Earth can change over time, might life
change as well?
• Realized it would take many, many years
for life to change in the way he suggested
– This would only be possible if the Earth were
extremely old!
Population Growth
• Malthus reasoned that if the human
population continued to grow unchecked,
sooner or later there would be insufficient
living space and food for everyone.
• Darwin asked a couple of questions:
– What causes death of so many individuals?
– What factors determine which ones survive and
reproduce and which ones do not?
Publication of “Origin of Species”
• Received a short essay from Alfred Wallace,
which summarized the thoughts on
evolutionary change that Darwin had
• NOW DARWIN HAD AN INCENTIVE
TO PUBLISH HIS OWN WORK!
• He proposed a mechanism for evolution –
called it natural selection!
Natural Selection Occurs Because of:
1. The Struggle for Existence
2. Survival of the Fittest
3. Descent with Modification
4. Genetic Variation
5. Overproduction of Offspring
INTRODUCTION TO EVOLUTION VIDEO
http://www.pbs.org/wgbh/evolution/library/11/2/e_s_4.html
5 parts of Darwin’s Theory of
Natural Selection
• Genetic Variation – Ultimate source =
MUTATIONS!
• Overproduction of Offspring
• Struggle for Existence
• Survival of the Fittest
• Descent with Modification
Organisms produce more
offspring than can survive.
• Example: A frog can lay 200
eggs, yet not all eggs
will survive to become
adult frogs.
Struggle for Existence
• Members of each species compete regularly
to obtain food, living space, ect.
• Prey – faster, better camouflaged, or better
protected
Survival of the Fittest
• How well an organism is suited to its
environment
• **Fitness – ability to change (adapt) in
order to be able to survive and reproduce
• Is this always the strongest or the biggest
organism????
Descent with Modification – Common
ancestor and change over time in a population
All living things are related due to common ancestorsPrinciple of “Common Descent”
Results of Evolution -- Speciation!!
• Speciation is the process that creates new species!
• A species is a group of organisms that can naturally
interbreed and produce fertile offspring.
• The Liger--the offspring of a tiger and a lion.
• Tigers and lions are still considered separate species, because
although they can produce
offspring, the offspring
is not fertile.
Evidence of Evolution
A. Fossils – Mineralized remains or imprints of organisms
from the past
“Missing Links” – Intermediate fossils between groups
of organisms
Fossil record is not complete!
B. Geographic distribution of living species
Species evolve differently in
different environments
Different species evolve similarly in
the same type of environment
C. Amino Acid Sequences (DNA Evidence)–
More closely related, more aa sequence similarities
should be seen
D. Anatomy–
Similar body structures that
don’t necessarily have
similar functions
(Homologous Structures)
Similar structures with
reduced size and lesser
function or no function
(Vestigial Structures)
Evidence of Evolution -Anatomical/Physiological Similarities
• Notice how there are similar bones and similar
structures in humans, birds and whales!
– Can you tell which is the bird and
which is the whale?
Analogous Structures
• Serve the same function but are
anatomically different. Serve as evidence
that the organisms evolved independently
Vestigial Organs
organ that serves no useful function
over generations, they reduce in size
Evidence of Evolution -Embryology!
• It is believed that all vertebrates evolved from a
common ancestor. The genetic
information that guides their
development is nearly the same.
• That's why scientists can learn about human
development by studying other organisms-including zebrafish.
E. Embryonic
Development –
Similarities in development
of embryos of organisms
Extinction!
• Extinction occurs
when there
are no members
of a species
left alive.
Evaluate the theory of evolution
Strengths
Weaknesses