SBI3U Evolution – Growing Evidence

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Transcript SBI3U Evolution – Growing Evidence

Evolution: Evidence
The Saga Continues…
More Evolution Humour…
What does the picture show?
• The concept of
evolution was
conceived piece by
• It was not
something that
developed overnight!
• There are still
pieces to be
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!
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 selfsustaining 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
Lamarck: If you want something badly
 While Lamarck was on the
right track, he also was a little
 He took the example of a
 What is their main
 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 
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
The boat took him to
the Galapagos Islands
where he made his
most famous
Darwin’s Journey
Darwin and his Finches
Evidence #1: Biogeography
 Darwin noticed that
close environments
are more likely to
be populated by
related species
 Animals found on
islands resemble
those found on the
closest continent
Darwin and his Finches
 Looking at the diagram,
what do you think caught
Darwin’s attention?
 Darwin noticed that Finch
species differed in beak
 He tried to devise a theory
that would explain the
diversity of the finches
Structure fits Function!
Evidence #2: Anatomy
 Homologous features are shared by two species that
are 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
Analogous Features
 A 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
Vestigial Features and Anatomical
Ever wonder why people get their
appendix removed?
Why do you think this is possible?
We do not need all the structures in our body
They 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
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…
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
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
More Vestigial Organs
Pelvic elements in pythonid snakes and
Vestigial Toes
Dogs, pigs, and horses have a digit that
serves no present purpose
Goosebumps – vestigial?
 What is the purpose of
 Why would they be
 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
Anatomical Oddity
Why does the
spermatic cord
go all the way
around and not
Match the Animal with its Embryo!
Evidence #3: Embryology
Your choices:
• Human
• Chicken
• Pig
• Cow
• Rabbit
• Fish
• Salamander
• Tortoise
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
What are fossils?
Any preserved remains or traces of an organisms or
its activity
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
These layers eventually become sedimentary rock
which preserves many specimens from our past
Archaeopteryx – A prime example!
Based on its Fossil…
Dangerous Ideas…
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 
How do we know the age of
fossils then?
Absolute age of fossils can be determined
through a technique called radiometric
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!
Evidence #5: DNA
 Two closely
related species
will share similar
DNA sequences
 All living things
undergo protein
synthesis using
Junk DNA?
Much of our DNA does not code for
anything – why is that?
95% is “junk!”
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
 GENES! (Genetics &
DNA) & mutations