Download Theory of Evolution

Aim #73: How do scientists explain the
development of life on earth?
1) What were the conditions on
earth 4.5 billion years ago?
1)Hot
2)Little Oxygen
3)Abundant Lightning
4) Volcanic Activity
Harsh Early Earth
2) Primitive Earth’s Energy Source
• As earth cooled,
thunderstorms drenched
the earth with water and
the oceans formed.
Lightning provided an
energy source for life to
begin.
3) How did life begin on earth?
Formation of Organic Compounds
• Inorganic
compounds
formed organic
compounds.
Amino Acids,
Nitrogenous Bases,
Monsaccharides,
Fatty Acids
Experiment by Stanley Miller & Harold Urey
4) Formation of Organic Polymers:
Scientists have proven that polymers of organic compounds
like polysaccharides, polypeptides, lipids and nucleic acids
could have formed during the conditions of early earth.
“RNA World”
Scientists hypothesize that the first genes were RNA. RNA
served as the both the molecule that stored the genetic info.
& the molecule that directed protein synthesis.
6) Formation of Pre-Cells:
Experiments show that membranes can form around
organic polymers in a solution if certain kinds of lipids
are present.
**The simplest living organisms are far more complex
than these “pre-cells”
7) Where did life begin?
Today’s deep sea vents are
populated with simple unicellular
organisms that may resemble
some of the earliest living cells.
8) First organism on Earth
Anaerobic
prokaryote cells
heterotrophs
The first organisms on earth
were simple unicellular
organisms.
9) Where did the oxygen come
from?
• Some of these early forms of life developed into
unicellular autotrophs (they got their energy
from the sun and produced oxygen)
10) Aerobic Organisms
Now, that the new atmosphere had
OXYGEN, organisms that could use oxygen
to do cell respiration slowly developed.
12) How do scientists explain this change
from simple to more complex organisms?
Theory of Evolution
1) The process by which
species change over time
(simple to complex).
2) Present day species are
related to ancient species.
12) What is a theory?
Theory of
Evolution
Is an explanation, supported by observations and/or
experiments, that can be used to explain related
occurrences.
13) 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
3) Similarities in Development (Embryology)
4) Molecular Biology (DNA & Proteins)
14) How do we know that we have
evolved from ancestors distinctly
different from us?
FOSSILS
Hint: How do we
know dinosaurs
existed?
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.
15) The fossil record shows…
• Life has evolved from simple to more
complex
Newer Organisms:
more complex
Older Organisms:
more simplistic
16) 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
Speciation
18) Evolution has lead
to the formation of new
species from different
ancient organisms
17) Species- a group of organisms that
share certain characteristics & can
mate with one another, producing
fertile offspring.
Similar to a family tree
• Descendents
Descendents
Common
Ancestor
19) Evolutionary Tree
Species living at
present time (top)
Ancestral common
species (bottom)
Our Common Ancestor
Unicellular
Common
Ancestor
100’s of
Millions of
year ago
How closely related are they?
• Which organisms are
closely related?
• Those who have a
recent common
ancestor (a close point
of intersection in a tree
diagram)
• Which are distant
relatives?
• Those who have a
distant common
ancestor (a far point of
intersection in a tree
diagram)
20) What organisms are our
closest relatives? Why?
Summary of early evolution
Present day