Transcript Topic: Evolution

Topic: Evolution
Aim: How did life evolve on Earth?
When did the Earth form?
• 4.6 billion years
ago
• Atmosphere: (air)
little O2, mostly
poisonous
chemicals
• Oceans: “soup” all
different chemicals
How did cells form?
• Chemicals in the ocean combined →
• Formed the building blocks of life →
• CELLS (3.5 billion years ago)
What did the first cells look like?
1. Anaerobic: no oxygen needed; heterotrophs
evolved
2. Cells that carry out photosynthesis;
autotrophs
evolved
3. Aerobic: uses oxygen
evolved
4. Multicellular organisms
Topic: Evolution
Aim: How do fossils support the theory of
evolution?
Do Now: Read the article. How does the article relate
to evolution? What is your reaction to the article?
What is evolution?
• Change in a species over time
• Species: group of organisms that share
similar characteristics and can interbreed
with one another to produce offspring
• Geologic time scale: calander of Earth’s
history
• PRECAMBRIAN – first 4 billion years (few
fossils)
What evidence is there for evolution?
•
•
•
Fossils: remains/evidence of a living
thing (bones, shells….)
Fossils form when organisms die → get
buried in sediments (particles of soil and
rock)
Some fossils become petrified – remains
change into rock
What is the fossil record?
• All the fossils scientists have collected
• Most complete biological record of life on
Earth
* Evidence that generations of species go
through changes *
What is an adaptation?
• Change that increases an organism’s
chances of survival
• May be caused by a mutation
Topic: Evolution
Aim: What other pieces of evidence besides
fossils support the theory of evolution?
Evidence of Evolution
1. Fossils
2. Anatomical evidence
• Homologous structures: body parts from
different organisms are similar in structure
(shape and arrangement)
• Examples: human arm
Suggest that all
bat’s wing
evolved from a
whale’s flipper
common ancestor
dog’s leg
Homologous structures
Evidence of Evolution
3. Embryological evidence
• Embryos of vertebrates are very
similar suggesting that they are
closely related (common ancestor)
Embryological evidence
Evidence of Evolution
4. Chemical evidence
• Similarities in DNA suggests closely
related organisms
5. Molecular evidence
• Similarities in the structure of proteins
suggests closely related organisms
What do all of these various types
of evidence tell us?
• LIVING THINGS HAVE DESCENDED
(EVOLVED) FROM A COMMON
ANCESTOR!!!
Topic: Evolution
Aim: How can the age of fossils be
determined?
How can the age of fossils be
determined?
1. Absolute dating (radioactive decay)
• Determines actual age
• Rocks that fossils are found in contain
radioactive elements
• Half-life analysis determine age of rock
How can the age of fossils be
determined?
2. Relative dating
• Which of 2 fossils is older?
• Sedimentary rock: layers of sediments that
pile up on top of each other over time (may
contain fossils)
• Law of Superposition: younger rocks/fossils
lie on top of older rocks/fossils
(young fossils → top layers
old fossils → lower layers)
Law of Superposition
Law of Superposition
1. Which layer is the
I
youngest?
2. Which layer is the
oldest? A
3. Which is older
layer C or F? Why?
C – lower layer
4. A fossil found in
layer G would be
Older
______
than a fossil
found in layer I.
Who is Charles Darwin?
• Explored/observed the Galapagos Islands
• Book: On the Origin of Species
• NATURAL SELECTION – idea used to
explain how evolution occurs
What is natural selection?
• Survival & reproduction of those organisms
best adapted to their surroundings
Causes of Natural Selection
1. OVERPRODUCTION
• Overproduction: when a species produces
more offspring than can be supported by the
environment
• Results in competition
• “Survival of the Fittest”: only the bestadapted members of a species survive
(nature selects the fittest = natural selection)
Causes of Natural Selection
2. VARIATIONS
• Variations: differences between organisms
of the same species that will allow them to
adapt and survive
• May be caused by mutations
Summary: Natural selection is based on the
two ideas – OVERPRODUCTION &
VARIATION
How long does it take evolution to
occur?
• Two theories
1. PUNCTUATED EQUILIBRIUM
• Evolution occurs
in rapid and sudden
changes in a species
after a long period
of little or no change
(usually after a mass
extinction)
How long does it take evolution to
occur?
2. GRADUALISM
• Evolution occurs gradually over time
Comparison: Punctuated Equilibrium &
Gradualism
Gradualism
Punctuated Equilibrium
***Both theories seemed to have
occurred during Earth’s History***