Download Evolutionary Theory Evolution

SBI 3U - UNIT 2
EVOLUTION
“Nothing in biology makes sense except in the light of evolution.”
Theodosius Dobzhansky
Hypothesis - a tentative assumption made in order to draw out and test its logical or
empirical consequences.
A hypothesis can be supported or refuted through experimentation or more
observation. A hypothesis can be disproven, but not proven to be true.
Theory
A scientific theory summarizes a hypothesis or group of
hypotheses that have been supported with repeated testing. A
theory is valid as long as there is no evidence to dispute it.
Therefore, theories can be disproven. Basically, if evidence
accumulates to support a hypothesis, then the hypothesis can
become accepted as a good explanation of a phenomenon.
One definition of a theory is to say it's an accepted
hypothesis.
Stephen Hawkin:
Stephen Hawking on Creation Myths and The Vatican.mp4
"A theory is a good theory if it satisfies two requirements: It must accurately describe a large
class of observations, and it must make definite predictions about the results of future
observations."
"No matter how many times the results of experiments agree with some theory, you can
never be sure that the next time the result will not contradict the theory. On the other hand,
you can disprove a theory by finding even a single observation that disagrees with the
predictions of the theory."
Evolution Isn't Evolution Just a Theory.mov
- Cell Theory
- General theory of relativity
- Wave theory of light
The theory of evolution and common descent were once controversial in
scientific circles.
This is no longer the case. Debates continue about how various aspects of
evolution work.
However, evolution is now a modern science and is universally accepted by
scientific community as the explanation for the origin of species and the histo
of life on earth.
Evolutionary Theory
Evolution - the process in which significant changes in the inheritable traits of
a species occur over time.
For centuries scientists have been making careful observations, formulating
and testing hypotheses, analyzing data from diverse sources and have
drawn inferences to develop the theory that is now accepted as the solution
to the puzzle of evolution.
Like all scientific theories the validity and value of evolutionary biology are
based on rigorous and continual analysis and interpretation of accumulating
evidence.
History of Evolutionary Theory
Paleontology (systematic study of fossils)
Began in the 18th century by Georges Cuvier.
Cuvier made many discoveries including:
Many fossils were of extinct species!
Fossils of simple organisms could be found at all depths of rock
strata.
Fossils of complex organisms were only found at shallower
depths.
More recent fossils were more likely to resemble living species.
Each layer contained distinct species not found above or below.
These findings puzzled Cuvier, as he did not believe species
changed, he believed all life had been created.
He came up the theory of CATASTROPHISM. He said that local
catastrophes such as floods could cause widespread extinctions,
and new species would be “created” to replace those lost.
This could account for the separation of fossils in strata layers, but
it could not account for the changing complexity of species.
The other problem for Cuvier was that there was no precise method for
calculating an absolute age of the rock or fossils.
Age of the Earth
Radioisotopes are atoms that undergo radioactive decay. These
atoms have an unstable nuclear arrangement and will undergo
decay to become stable atoms.
(Isotopes have same # of p+ but different # of no)
Ex. 235U decays into 207Pb
14C decays into 14N
It is the rate of decay that makes radioisotopes so valuable, because the
rates are constant.
The time it takes for half of the radioactive substance to decay is called
the half-life.
Ex. 235U decays into 207Pb with a half-life of 713 million years.
14C decays into 14N and has a half-life of 5730a
Half-life is unaffected by temperature, moisture or other environmental
conditions.
With the discovery of Radioisotopes came the technique of Radiometric dating which
uses half-lives as a naturally occurring clock.
A sample of igneous rock contains small amounts of radioactive potassium and argon.
Using the ratio of 40Ar to 40K , it is determined that only 25% of the original parent
potassium isotope remains. How old is this rock sample?
1. A sample of igneous rock is found to contain the radioactive parent and daughter
isotopes uranium, 235U, and lead, 207Pb, in the ratio of 12.5%:87.5%. Assuming that
no 207Pb was present when the rock first formed, estimate the age of this sample.
2. A fossil skull of Homo neanderthalensis, is discovered in northern Europe and is
tested using carbon-14 dating. Palaeontologists are curious about whether the
Neanderthal was living at the same time as members of H. sapiens, thought to have
been living in the same area of northern Europe 45 000 years ago. Measurements
suggest that, of the original amount of carbon-14 isotope present in the skull when
the Neanderthal died, only 1.56% remains in the fossil fragment.
(a) How old is the fossil?
Using this type of dating the following has been found:
All meteorites to hit the earth have yielded an age of 4.6 billion years.
Moon rocks have all been dated to about 4.43 billion years
Oldest rock on earth dated to 3.9 billion years.
This leads us to believe that the earth is approximately
4.6 billion years old.
Early Ideas About Evolution
1795
– James Hutton proposed ACTUALISM
– Same geological processes occurring in the present also
occurred in the past.
- Hutton explained the geological formation of landforms as the
result of slow processes.
– Contrasts Cuvier’s catastrophism
18th century
- Georges Buffon first to propose that species could change
over time and that changes could lead to new species
- Carl Linnaeus proposed that relatively few species had
formed many new species through hybridization and
interbreeding.
1830
- Sir Charles Lyell proposed UNIFORMITARIANISM.
- Theory that Earth’s surface has always changed and continues to
change through similar, uniform and very gradual processes.
- The work of Hutton and Lyell led to two significant conclusions:
that Earth must be unimaginably ancient and that dramatic change
could result over such extremes of time through slow, seemingly
slight processes.
19th century
-Jean-Baptiste Lamarck was the first to recognize the key role
played by the environment in evolution. He reasoned that in
order for survival over long periods of time, species must be
able to adapt to the changing environment.
-Where he went wrong was that he believed each species
gradually became more complex and that new simple species
were continually being created by SPONTANEOUS
GENERATION (living arise from non-living)
- He believed in inheritance of ACQUIRED TRAITS or
those changes in an individual resulting from interaction
with the environment.
- EX. Giraffes neck
1831-1859
- Charles Darwin
- In 1831 Darwin boarded H.M.S. Beagle as a naturalist for a 5-year
costal mapping trip to South America.
- Darwin was taken on the trip in hope that he would find evidence
to support biblical creation.
- He collected thousands of specimens and recorded thousands of
journal entries
- The most important stop on the voyage was to the Galapagos
Islands.
- Here he found that the flora and fauna resemble that of S.
America but seemed to have its own unique traits.
- At the time he failed to realize that each island supported
unique species of plants and animals.
- Ex. Darwin’s Finches
When Darwin returned to England, he was full of enthusiasm and questions.
His subsequent analysis of the evidence over the next 28 YEARS led him to
write the most biologically significant paper ever:
“The Origin of Species”
Evolution Who
Was Charles
Darwin.mov
Darwin would question many things he had observed in
his travels and would provide new ideas and powerful
lines of evidence for his theory of evolution.
Reading:
On the Origin of Species
What Darwin Observed
Many unusual fossils resembled currently living species in the
same region.
Ex. Glyptodon and Armadillo
Of the 13 finches he brought back from the Galapagos Is. 13 were
different species, none found anywhere else on earth and all similar to
one species found on the closest land mass.
1. Large cactus finch (Geospiza conirostris)
2. Large ground finch (Geospiza magnirostis)
3. Medium ground finch (Geospiza fortis)
4. Cactus finch (Geospiza scandens)
5. Sharp-beaked ground finch (Geospiza difficilis)
6. Small ground finch (Geospiza fuliginosa)
7. Woodpecker finch (Cactospiza pallida)
8. Vegetarian tree finch (Platyspiza crassirostris)
9. Medium tree finch (Camarhynchus pauper)
10. Large tree finch (Camarhynchus psittacul)
11. Small tree finch (Camarhynchus parvulus)
12. Warbler finch (Certhidia olivacea)
13. Mangrove finch (Cactospiza heliobates)
The Galapagos contained only birds and land animals like lizards
and turtles. No mammals.
Led to ideas about initial populations and isolation mechanisms.
Darwin not only compared species based on their external features
but also was interested in comparing body parts of seemingly
unrelated organisms.
He found that body parts with entirely different
similar in structure.
functions were
HOMOLOGOUS FEATURES
Structures that share a common origin but may serve
different functions in modern species.
All of these parts include the same bones in the same relative positions.
Evolution Assignment 2 - Activity 11.5.1 Biology 12
LOOKING FOR HOMOLOGIES
ANALOGOUS FEATURES are structures
similar in function but not in origin or
anatomical structure.
The wings of bats, butterflies and birds, or
the eyes of lobsters and fish were
observed to be different in internal
anatomy.
Darwin concluded that organisms with homologous features likely
shared a more recent common ancestor.
grasshopper
bee
platypus
human
bat
Sometimes homologous features only appear during embryonic
development.
These similarities were first noted biologist Ernst Mayr
Mayr noted if evolution is not true, "why should the embryos of birds
and mammals develop gill slits, like fish embryos?"
Darwin also studied numerous VESTIGIAL FEATURES. Theses
are structures that serve no useful function in a living organism
Ex.1 The digits in dogs, pigs and horses.
Ex. 2 - Wings of some beetles under fused elytra (covers)
Ex. 3 - Humans have muscles for moving ears
Ex 4. Some snakes and large whales have vestigial hips!
Ex. 5 - Upland geese and frigate birds have fully webbed feet but
never enter water.
Ex. 5 - Ostriches - Flightless birds.
Ex. 6 - Blind Astyanax Mexicanus.
Ex. 7 - Human Tailbone ( Coccyx)
With our knowledge of DNA, we have now found a large
# of vestigial genes. Genes that do not function but are
almost identical to those that are functioning in other
organisms.
L-gulano-γ-lactone oxidase gene, required for Vitamin C synthesis,
was found in humans, other primates and guinea pigs
Based on DNA sequences for this pseudogene in
chimpanzees, orangutans, and macaques the human gene
is most similar to chimpanzees, followed by orangutan, and
then macaque, precisely as predicted by evolutionary
theory.
Attachments
Stephen Hawking on Creation Myths and The Vatican.mp4
Evolution Isn't Evolution Just a Theory.mov
Evolution Who Was Charles Darwin.mov