Download Theory and Evidence of Evolution

AIM: How Do Scientists explain
and support the theory of evolution?
What is a theory?
Is an explanation supported by
observations and/or experiments, that
can be used to explain related
occurrences.
Theory of Evolution
Theory of Evolution
1)The process by which species change
over time (simple to complex).
2)Present day species are related to ancient
species.
Scientists use this theory to explain a
change in a species from simple to
more complex organisms?
What is the Theory of Evolution?
• The gradual change of different
organisms and species over time
that allows them to adapt to a
changing environment.
What is the evidence that supports
the Theory of Evolution?
1) Fossil Record - collection of fossils that
provides clues to the history of Earth’s
organisms. The fossil record spans much of
geologic time (billions of years of Earth’s
history).
2)Similarities in Structure (body structures)
3)Similarities in Development
(Embryology)
4)Molecular Biology (DNA & Proteins)
How do we know that we have evolved
from ancestors distinctly different from
us?
Hint: How do we
know dinosaurs
existed?
FOSSILS
The fossil record (remains of dead
organisms) have given scientists the clues
they needed to determine an organisms
ancestry by comparing them to present day
species.
The fossil record shows…
Life has evolved from simple to more
complex
Newer
Organisms:
more complex
Older
Organisms:
more simplistic
What do we learn from fossils?
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
• How did behaviors evolve?
• How long did individuals live?
• How do features evolve over time?
http://www.ucmp.berkeley.edu/education/explorations/tours/stories/middle/C7a.html
Evolutionary Tree
Species living at
present time
(top)
Ancestral
common species
(bottom)
Similar to a family tree
• Descendents
Descendents
Common
Ancestor
Our Common Ancestor
Unicellular
Common
Ancestor
100’s of Millions
of year ago
How closely related are they?
• Which organisms • Which are distant
are closely
relatives?
related?
• Those who have
• Those who have
a distant common
a recent common ancestor (a far
ancestor (a close point of
point of
intersection in a
intersection in a
tree diagram)
tree diagram)
What organisms are our closest
relatives? Why?