Transcript Picture

Everything must evolve…
Charles Darwin
• Father of Evolution
• Proposed a way how
evolution works
– How did creatures
change over time?
– by natural selection
• Collected a lot of
evidence to support his
ideas
– 1809-1882
– British naturalist
Voyage of the HMS Beagle
• Invited to travel around the world
Voyage of the HMS Beagle
• Stopped in Galapagos Islands
– 500 miles off coast of Ecuador
Darwin found… many unique species
Many of Darwin’s observations made
him wonder… Why?
Darwin asked:
Why were these creatures found only on the
Galapagos Islands?
Darwin found… clues in the fossils
Darwin found:
Evidence that creatures have
changed over time
present day Armadillos
Darwin asked:
ancient Armadillo
Why should extinct
armadillos & modern
armadillos be found on
same continent?
Darwin found:
Different shells on tortoises on different islands
Darwin asked:
Is there a relationship
between the environment
& what an animal
looks like?
The finches clinched it for Darwin
Darwin concluded:
Each species has descended, with changes, from other
species over time.
Darwin called this…
Descent with modifications
or
(change in population over time)
Data supports
Evolutionary Theory
Darwin’s Theory of Evolution by
Natural Selection
• Species have changed through time and
are related by descent from a common
ancestor
• The primary mechanism of Evolutionary
Change is Natural Selection
Fossil Record - the history of life recorded by
remains from the past. Most fossils are at least
10,000 years old.
1. Body Fossils
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2. Trace Fossils
What is found?
- Fossils exist and fossil forms are unlike species living today
1. Fossil Sequence?
When fossils are arranged according to
their age, they show successive
evolutionary change
2. Fossil Intermediates?
Transitional fossils have been found between:
Amphibians & reptiles, reptiles & birds,
reptiles & mammals, apes and humans
The Evolution of Horses
A particularly well-documented case of evolution within a group
The Fossil Record is Incomplete
At the time of Darwin, the fossil record was VERY scanty. A
great deal of progress has been made since, but it is far from
finished.
The fossil record is relatively incomplete for several reasons:
1. Soft tissues are rarely preserved
2. Movement of the earth's crust has obliterated and/or
covered many fossils
3. Fossilization takes place only in certain types of
habitats and favorable environments
4. Paleontologists have not dug up every place on earth
Even if there were no fossil
record, the evidence from living
organisms would be more than
sufficient to demonstrate the
historical reality of evolution
Vestigial Structures
• Features that have no apparent function
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• Typically have an important function in related species
Vestigial structures
Ex: Hindlimb
joints in whales
and snakes
Vestigial Structures in Humans
Tailbone
Wisdom Teeth
Appendix
Evidence for the relatedness of life
forms?
• Hypothesis: all living organisms have
descended from a common ancestor
• Prediction: we should also be able to see
evidence of relatedness of species
-Homology
-Geographic distribution
Homology
• Homology: a similarity between species that
is the result from the inheritance of traits from a
common ancestor
•The features of every creature reflect history
as well as adaptation
• 3 types of homologies
- structural
- developmental
- genetic
Analogous Structures
 Different structures, same function
 Suggests that organisms do not share a close

common ancestor
Ex. Hawk, butterfly, & bat can all fly but have
different wing structure
Homologous Structures
• Same structure in different animals
• Suggests that organisms share common ancestor
• Ex. Forelimbs of human, cat, whale, & bat
Same bone
structures
Homology vs. Analogy
Natural selection appears to have favored similar adaptations
in unrelated organisms in similar environments-->
these structures are analogous
Whereas homologous structures
share structural similarity, but not
function, analogous structures
share function but not structural
similarity since they evolved
independently
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display
Embryos show evolutionary history
Homologous structures in adults develop from homologous groups
of cells in embryos --> they share developmental pathways
Comparative Embryology
• Analyzing embryos with similar structures to show
common ancestor
Dog
Fetus
Human
fetus
Bat Fetus
Genetic Homologies
All living organisms share the same
genetic code
Chromosome and gene similarities between
species match evolutionary similarities
This is true for both coding regions and
“junk DNA”
Molecules reflect evolutionary divergence
Geographic Distributions
Species that are extremely similar to one another tend to be
clustered geographically (Ex.: Darwin’s finches)
Living species are more similar to fossil species in the same area
than they are to living species in other areas
•The law of succession
–general correspondence between fossil and
living forms in same geographical area
Darwin used this observation to predict that fossils
of ancient humans should be found in Africa
That Evolution Has Occurred Is
A Fact
Fossil Record Evidence of Evolution
How to estimate how old:
1) the deeper the layer that the fossil is found in, the older it is
2) the fossils near the surface are younger and more complex
5
4
3
2
1
Which rock layer is
the oldest?
Which fossil is
older: a fossil in
layer 4 or a fossil in
layer 2?
What observations
did you make about
the organisms in
layers 1-3 and 4-5?
What does this tell
you about the type
of environment?
• Although scientists have a found a lot of fossils (and still continue to find them!), they
still have missing pieces in the fossil records of species.
• The camel however, has a nearly complete fossil record of it’s evolution
Change by Chance Activity
Procedures:
1. You will need a pencil for this activity. You will be working with a group of students and drawing a
picture. You cannot look at anyone else’s drawing.
2. The drawing should be face down until the signal to begin is given.
3. I will signal the beginning and end of each 15-second interval.
4. I will give the first student in each line 15 seconds to draw, not trace, the image on the colored paper
onto their blank paper.
5. The first student will then pass their drawing to the next person. The second student in each row 15
seconds to draw, not trace, the first student’s drawing on his or her own paper.
6.
At the end of the 15 seconds, the second students pass their drawings to the third students, and
so on until all students in a group have had a chance to draw the reptile.
7. Have each group label all of their drawings with a group name, mix the order, and place them
together.
8.
I will collect each group’s drawings and redistribute each set to a different group. In groups,
sequence the order of the drawings and then tape them on the wall.
9.
Choose one person from the original group confirm the accuracy of the sequencing.
• Why was sequencing the drawings difficult?
• How was this experience similar to sequencing
fossil records?
• How was this experience different from
sequencing fossil records?
Turn to an elbow partner and answer
the question below. Discuss how to
determine the correct answer.
With the same elbow partner describe the
changes in the fossils you see in each layer
and what they tell you about that time period.
Turn to a different partner. Compare layer C to
layer F in the diagram below. What evidence
do these fossils provide of changes on earth?
Living or once living things share
common ancestors and fossils
provide evidence for common
ancestry.
Changes in fossil
records…. What do
they mean?
Stasis •
In this picture, the color of the moths
changes very little.
Punctuated equilibrium is a
evolutionary theory which proposes
that once species appear in the fossil
record they will become stable,
showing little net evolutionary change.
Gradualism - suggest that organisms evolve
through a process of slow and constant change.
• For instance, an
organism that shows a
fossil record of
gradually increased size
in small steps, or an
organism that shows a
gradual loss of a
structure.
In the case of the moths above, they
gradually change color over time.
Physical
characteristics of
organisms change
over time and fossils
provide evidence of
change.
Summarizing Strategy: 3 – 2 – 1
Describe three ways in which scientists support
the theory of evolution.
Identify two ways in which scientists know the
physical characteristics of organisms change
over time.
Describe why the fossil record is important.