“A change in the frequency of an
allele within a gene pool.”
-Wikipedia
Evolution
Notes
What does this unit (“change over
time”)cover?
In this unit we will study:
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Geologic Time Scale
Fossil Formation
Animal Behaviors (based on fossil evidence)
Hypotheses' and theories about the origins
of life
▫ Structures, DNA, and embryology!
▫ Chapters 14 and 15 in your book!
To understand evolution, we must
first understand…
•Evolution is based on Science.
• Science only attempts to explain
the natural world – not the
supernatural world.
• In science, evolution is the best
explanation we have right now as
to how life has changed on earth
over the last few billion years.
•Evolution is not a debate in
the scientific community.
• Evolution is a well researched
scientific theory supported by
thousands of scientific studies and
many different types of evidence.
• The word “theory” in science is synonymous
with the word fact. It means the idea must be
supported by hundreds of thousands of pieces of
evidence, gathered by many different scientists,
whom over many years, reach the same
conclusion.
• When scientists label an idea a theory, they are
saying they are 99.9% sure this is the way it is!
• We don’t “BELIEVE” in evolution, we
study it… just like photosynthesis,
mitosis or any other biological
process.
• Do you BELIEVE in mitosis?
So, what is evolution?
• Evolution means “change over time”.
• Organisms must adapt and change over time to
become better suited (live longer) to their
environment.
• The key is to live long enough to pass down the
“good genes” to their offspring!
• All living organisms evolve – from bacteria to
humans!
How do we know evolution occurred?
• Fossils
• Structures in modern animals that are no longer
useful
• Embryological comparisons
• DNA and comparative biochemistry
• Skeletal structures (comparative anatomy)
• Geographic distribution
• Adaptations
Chapter 14 (Fossils)
• Fossils:
▫ Trace fossils (left by a soft part like a footprint) vs.
cast and mold fossils (left from a hard part like a
shell or bone) Both important!
▫ Types of dating:
 Relative – general idea (older than or younger than
another fossil)
 Absolute – specific date, done by carbon dating or
radiometric dating
▫ Law of Superposition – older fossils are lower in
the rocks, younger fossils are closer to the top
layer of soil
▫ Strata or Stratum – layers of rock,
usually different colors or made of
different types of rock
▫ Type of rocks fossils are found in –
sedimentary
▫ Whale skeletons and horse skeletons as
evidence of evolution
Fossils
•
What is a fossil?
▫
•
Preserved evidence of an organism
How is a fossil formed? (page 394)
1. Organism dies and is buried in sediment
2. Sediments build up and cover remains
3. Minerals in water fill empty pores in hard parts
that remain
4. Organism’s soft parts decay, leaves its
impression (or mineralized hard parts)
5. Sediments eventually harden into rock
• Mold – impression in the rock
• Cast – hard part that is mineralized (fills up the
mold)
• 2 types of fossils we will see in our lab
▫ Trace fossil: footprints, burrows, indirect evidence
▫ Cast and Mold fossil: impression/hard part that is
fossilized
• 4 more are found on page 393
• Geologic Time Scale – A record of what
fossils showed up at what time in the past.
•
•
•
•
Eras from oldest to most recent
Longest era? Precambrian
Current era? Cenozoic
Cambrian Explosion (many life forms emerge,
what era? Paleozoic Era)
• KT Boundary provides possible evidence of a
meteorite strike (what era? Cenozoic)
• Many other important events, check out pages 397
in your book!
End of Day 1 of Guided Notes
• Handout: Geologic Time Scale WS
History of the Earth
• Estimated age of the Earth – 4.6
billion years
• Earth’s early existence – what did it
look like?
Perhaps like this?
• Origins of life
▫ Spontaneous generation, disproved by Redi
▫ Biogenesis, evidence provided by Pasteur
▫ Primordial soup – this is an old idea and scientists have
new ideas now. They used to think lightening hit and
caused the fusion of organic compounds and that was
how life started.
▫ Hydrothermal vents – this is the more current thinking.
Life could have begun under the oceans by small bacteria
that “chemosynthesized”. We have found similar
organisms in the modern day.
Once life started… Cellular Evolution
• Earliest fossils found, 3.5 billion years ago
• First cells – prokaryotes – like modern day Archaea
(live in hot springs and harsh environments, need no
oxygen or sunlight)
• Oxygen present in early Earth bonded to iron until
the iron was “full” or saturated. Then it began to
accumulate in the atmosphere.
• Next to evolve – photosynthesizing prokaryotes, like
cyanobacteria, these we have fossils of (3.5 bil. Yrs.
Ago)
• The cyanobacteria eventually produced enough
oxygen to make the ozone layer
• Once that was done, eukaryotic cells started to
appear!
• Then we see many types of life forms starting to
appear in the fossil record.
• Endosymboyant Theory – Margulis 1966
▫ States that the ancestors of eukaryotic cells lived
in close association with prokaryotic cells or even
inside of each other. This was a mutualistic
relationship!
• 2 organelles involved (evidence)
▫ Chloroplast and mitochondria, why?
 These organelles both have their own DNA (which is
in the same shape as prokaryotic organisms), have
ribosomes that are like those of prokaryotes, and
they reproduce by fission (like prokaryotes).
Chapter 15
• Examples of topics scientists study and use as
evidence of Evolution:
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Embryology
Comparative Biochemistry (Macromolecules)
Biogeography
Vestigial Structures
Homologous Structures
Analogous Structures
• Acquired Traits – things you acquired and are not genetically passed
down to you (like large muscles or good handwriting skills)
▫ These are NOT examples of evolutionary genetic changes.
A man named Charlie D…
• Background about Charles Darwin…
One of Charles Darwin’s most famous studies was
on the Galapagos Islands (I’ve been there!!!).
He collected a lot of information on Finches.
• Darwin’s 2 Conclusions
▫ Decent with Modification: The newer forms
appearing in the fossil record are actually the modified
descendants of older species.
▫ Modification by Natural Selection: The process by
which organisms with favorable variations reproduce at
higher rates than those without such variations.
• Darwin info…
▫ Beagle (his ship), Finches (the birds he studied),
Galapagos (famous islands), his book (The Origin of
Species), his life (we will watch a video about it!)
Definition:
• Biological Fitness – high fitness means you can
create a high number of viable offspring (they
don’t die)
• Divergent Evolution – one species looks more
and more different (finches)
• Convergent Evolution – 2 species look more
and more similar (shark and dolphin)
• Types of Selection
▫ Artificial - breeding organisms on purpose, done
by humans – dog breeders
▫ Natural - 4 contributing factors: Variation,
Heritability, Overproduction, and Reproductive
Advantage. (page 421)
▫ Sexual – the male and female organisms look
drastically different (peacocks)
• Camouflage – blending in (Chameleon)
• Mimicry – looking like another organism (snakes)
• “Favorable Traits” – things that are helpful traits
that have evolved from our ancestors
• Bacterial Evolution
▫ Mutations are “mess ups” in the DNA
▫ Cause bacteria to change and become resistant to
antibiotics
▫ Also seen in virus’ like HIV which can evolve in
minutes or hours!
• Cladograms – diagrams that show evolutionary
relationships
Cladogram - Example
End of Day 2 Guided Notes
Now let’s look at…
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Embryology
Comparative Biochemistry (Macromolecules)
Biogeography
Vestigial Structures
Homologous Structures
Analogous Structures
Embryology
• Scientists can look at the very beginning stages
of development for an organism and compare it
to other organisms to determine how similar
(closely related) those organisms are to each
other.
• Let’s take a look!
Can you tell what is what?
Can you identify
the:
Chicken
Rabbit
Fish
Human
Tortoise
Cow
Salamander
Pig
How about now?
Can you identify
the:
Chicken
Rabbit
Fish
Human
Tortoise
Cow
Salamander
Pig
Ok, here’s the last one!
Can you identify
the:
Chicken
Rabbit
Fish
Human
Tortoise
Cow
Salamander
Pig
Answers!
Comparative Biochemistry
(Macromolecules)
• Scientists now know the DNA sequence of
humans (and many other living organisms)
• We can compare our DNA or other biological
molecules to see how closely they match up with
other organisms. The closer the match, the more
recent the common ancestor.
• Let’s see an example…
Human Cytochrome C
http://bioweb.cs.earlham.edu/9-12/evolution/HTML/live.html
• Biochemistry also reveals similarities between
organisms of different species.
• For example, the metabolism of vastly different
organisms is based on the same complex
biochemical compounds. The protein cytochrome c,
essential for aerobic respiration, is one such
universal compound.
• The universality of cytochrome c is evidence that all
aerobic organisms probably descended from a
common ancestor that used this compound for
respiration.
• Certain blood proteins found in almost all
organisms give additional evidence that these
organisms descended form a common ancestor.
• Such biochemical compounds, including cytochrome c
and blood proteins, are so complex it is unlikely that
almost identical compounds would have evolved
independently in widely different organisms.
• Further studies of cytochrome c in different species
reveal variations in the amino acid sequence of this
molecule. For example, the cytochrome c of monkeys
and cows is more similar than the cytochrome c of
monkeys and fish.
• Such similarities and differences suggest that monkeys
and cows are more closely related than are monkeys
and fish.
• Scientists have similarly compared the biochemistry of
universal blood proteins. Their studies reveal evidence
of degrees of relatedness between different species.
This evidence implies that some species share a more
recent common ancestor than other species do.
Biogeography
• Some animals look similar to other animals in
different parts of the world
• Migration!
• Evolution is linked with climate and geological
forces (plate tectonics).
Vestigial Structures
• “Stuff we don’t need anymore but we must have
needed it way back in the past”
• Definition: Structures that are reduced forms of
functional structures in other organisms.
• Gives us a clue as to how that organism has
changed over time!!!
• Examples:
Examples of Vestigial Structures
• Snakes have tiny pelvic
bones!
• Whales have tiny pelvic
bones, even today!
▫ Why?
• Kiwi wings – much to small,
can’t fly.
▫ Why would a bird have wings
if it can’t fly?
• Appendix – important in
digestion for many
mammals, but not humans!
Human Vestigial Structures
Homologous Structures
• Anatomically similar
structures inherited
from a common ancestor
• “Same setup” – the
limbs of many
organisms have the same
basic anatomy
Analogous Structures
• Anatomically similar but not evidence of evolution
• Can be used for the same purpose and similar in
construction but not inherited from a common
ancestor