evolution: evidence the saga continues… more evolution humour…
TRANSCRIPT
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Evolution: Evidence
The Saga Continues…
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More Evolution Humour…
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What does the picture show?
• The concept of evolution was conceived piece by piece
• It was not something that developed overnight!
• There are still pieces to be discovered
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Evolution is a Unifying Concept that has many “Puzzle Pieces”
It has taken 100’s of years for Evolution to become a strong Scientific concept
Copernicus and Galileo were shunned for their Scientific proposals that are currently understood as fact and truth
Just as Copernicus cast the earth out from the center of the universe, evolution has displaced humans as the epicenter of the natural world
Keep an open mind!
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Early Ideas About Evolution
Early thinkers could not ignore their observations of the life around them
Lamarck was the first Biologist to recognize the key role of the environment in evolution
Lamarck theorized that species can be self-sustaining as long as they are able to adapt to the changing environmental conditions
Let’s look at a couple of examples in the animal world
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Lamarck: If you want something badly enough…While Lamarck was on the
right track, he also was a little off!
He took the example of a giraffe
What is their main adaptation?
He believed that if a giraffe tried stretching their neck long and hard enough, it would lead to its elongation; this trait would then be passed on to its offspring
He tried
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Charles Darwin: He’s da Man!
Went on a boat called HMS Beagle in 1831 and developed one of the most influential theories in human history
The boat took him to the Galapagos Islands where he made his most famous discoveries
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Darwin’s Journey
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Darwin and his Finches
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Evidence #1: Biogeography
Darwin noticed that geographically close environments are more likely to be populated by related species
Animals found on islands resemble those found on the closest continent
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Darwin and his Finches
Looking at the diagram, what do you think caught Darwin’s attention?
Darwin noticed that Finch species differed in beak size
He tried to devise a theory that would explain the diversity of the finches
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Structure fits Function!
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Evidence #2: Anatomy Homologous features are shared by two species that
is similar because of common ancestry For example, forelimbs of the following organisms are
adapted to carry out very different functions but have very similar bone structure
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Analogous FeaturesA feature/structure that serves the same function in
two species, but is NOT derived from a common ancestral structure is said to be analogous
For example, the wings of bats, insects, and birds allow these animals to fly but they do not share a common ancestor
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Vestigial Features and Anatomical Oddities
Ever wonder why people get their appendix removed?
Tonsils?Why do you think this is possible?
We do not need all the structures in our bodyThey do not serve any useful function These are called vestigial features:
rudimentary and nonfunctioning structures that are homologous to fully functioning structures in closely related species
Examples?
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Vestigial Features
Actually, now it’s believed that the appendix is part of the immune system, strategically located at the entrance of the almost sterile ileum from the colon with its normally high bacterial content
Originally, scientists believed they were evolutionary “left-overs”
Hmmm…
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What about the tonsils?
The tonsils have a similar function in the entrance to the pharynx (possible immune function)
Doctors have found higher occurrences of respiratory issues in patients who have had their tonsils removed
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Vestigial Structures in Whales
Hipbones are used to transfer body weight to the hind legs
What use do whales have for these?Whales are also mammals - perhaps they
are descendents of ancestral mammals that possessed hind legs
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More Vestigial Organs
Pelvic elements in pythonid snakes and cetaceans
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Vestigial Toes
Dogs, pigs, and horses have a digit that serves no present purpose
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Goosebumps – vestigial?
What is the purpose of goosebumps?
Why would they be vestigial?
The function in human ancestors was to raise the body's hair, making the ancestor appear larger and scaring off predators
Raising the hair is also used to trap an extra layer of air, keeping an animal warm (this function is not vestigial of course) but the reflex to form them under stress is
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Anatomical Oddity
Why does the spermatic cord go all the way around and not directly?
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Evidence #3: EmbryologyMatch the Animal with its Embryo!
Your choices:
• Human
• Chicken
• Pig
• Cow
• Rabbit
• Fish
• Salamander
• Tortoise
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Evolution has been Constructed with a lot of Help!
It was NOT only Biologists that contributed to the current understanding of Evolution
Paleontologists and Geologists have provided what some consider as the best evidence
This evidence is referred to as the fossil record
What are fossils?Any preserved remains or traces of an organisms or
its activity
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Evidence #4: Fossils
Most easily recognized by hard body parts like shells, bones, and teeth
Can include footprints, impressions of burrows, and chemical remains
How do they form?Remains of dead organisms become trapped in
sediments (particles of dirt and soil) which become compressed by gravity and pressure from layers above
These layers eventually become sedimentary rock which preserves many specimens from our past
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Archaeopteryx – A prime example!
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Based on its Fossil…
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Dangerous Ideas…
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Evidence from the Fossil Record
Fossils appear in chronological order in the rock layers
Paleontologists can trace back ancestry based on the physical similarities and age of the fossils
Horse toe evolution based on fossils
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How do we know the age of fossils then?
Absolute age of fossils can be determined through a technique called radiometric dating
This theory is based on radioactive decay (elements break down over time and release radioactive energy that can be measured) and the half-life of radioisotopes
How old is the Earth? About 4.6 billion years old!
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Evidence #5: DNA
Two closely related species will share similar DNA sequences
All living things undergo protein synthesis using RNA
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Junk DNA?
Much of our DNA does not code for anything – why is that?
95% is “junk!”
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It all comes down to Survival
Those organisms better suited to their environment will live to reproduce and leave offspring behind
Therefore, favourable variations are preserved and unfavourable ones are lost
What is the basis for variation? GENES! (Genetics &
DNA) & mutations