Theory of Evolution
Bio 20
An Important Note
• Evolution is a key part of biology
• Some people feel it is in conflict with their religious
beliefs about creation
• Many scientists are religious, and many religious people
accept evolution
– It’s up to each person to decide how to reconcile these two
aspects
• You are NEVER graded on your beliefs in the class – I’m
not trying to make you “believe” in evolution
• However, you DO need to understand the theory, the
evidence in support of it, and its implications
Who Was Charles Darwin?
• Darwin was born in 1809 in England. He attended
college to become a naturalist and clergyman
• When he was 22 years old he sailed on the
H.M.S. Beagle as the ship’s naturalist
• He collected many animal and plant specimens
from South America, documenting their diversity
• Darwin was struck by the unique animals of the
Galapagos islands in particular
Who Was Charles Darwin?
• http://www.pbs.org/wgbh/evolution/library/1
1/2/quicktime/e_s_2.html
(7 min)
Timeline Of Evolutionary Thought
• 1785 – James Hutton proposes that the Earth is
shaped by geological forces that happen over
long periods of time; estimates the Earth to be
millions (not thousands) of years old
• 1798 – Thomas Malthus writes an essay which
predicts that the human population will grow
faster than the space and food to sustain it
• 1809 – Jean-Baptiste Lamarck publishes his
hypotheses about the inheritance of acquired
traits. His ideas were flawed, but his is the first to
propose a mechanisms for evolution
Lamarck’s Ideas
Timeline Of Evolutionary Thought
• 1831 – Darwin sets sail on the Beagle, a voyage
that will provide evidence for his theory
• 1833 – Charles Lyell explains the processes
occurring now have changed Earth over long
periods of time
• 1858 – Alfred Wallace writes to Darwin with his
own speculations on evolution by natural
selection, based on his observations in Malaysia
• 1859 – Darwin publishes his book On the Origin
of Species
Developing Darwin’s Theory
• Suspected that living forms of similar
organisms may have descended from an
ancient ancestor
• Different landmasses acted like isolated
nurseries in which sets of species could evolve
independently
• Predicted that the 13 different species of
finches on the Galapagos all evolved from a
single ancestor species from South America
Developing Darwin’s Theory
• Became convinced that geological forces
could account for the location of fossils and
formation of mountains
• Figured nature must have a natural force
similar to artificial selection
• Used information from Thomas Malthus’,
Essay on the Principle of Populations to finish
his theory
Developing the Theory
• Malthus showed that all species produce far
more offspring than can be expected to
survive
• Darwin realized this led to an intense
competition, he called this the theory of
evolution by natural selection
• Alfred Russell Wallace independently arrived
at the same conclusion as Darwin, while
working in Malaysia
Observations & Inferences
– Observation 1: individuals within any species exhibit
inherited variations
– Observation 2: More offspring are produced than can
survive
– Observation 3: Populations tend to remain stable
– Inference 1: Individuals of a species are in a constant
struggle for survival
– Inference 2: Favourable variations make individuals more
likely to survive and pass on these traits. This is natural
selection
– Inference 3: These favourable variations will become more
prevalent in future generations. This is evolution
Evidence from Fossils
• Paleontology (study of fossils) has produced
strong evidence for a changing earth by providing
direct physical evidence of past life
• Patterns found:
1. Most species are now extinct
2. There is a systematic progression from only
very simple organisms to more complex ones
3. Living species and their most closely
matching fossils are typically located in the
same geographic region
Fossil Evidence Video
• https://www.youtube.com/watch?v=ewtw_nZ
UIDQ&list=PL5270149AB732F0FB&index=3
(7min)
Your Inner Fish
• Excerpt from Neil Shubin’s new book
• Current paleontologist
• Found a really important fossil in Canada
Evidence from Biogeography
• Biogeography explores the variation and
distribution of life on Earth’s surface today and in
the past
• Continental drift has caused major changes to
Earth’s landmasses
– http://www.youtube.com/watch?v=5ppyGg3vRs8
(1.5 min)
• Fossils of species from more than 150mya were
once found in the same geographic location
Evidence from Biogeography
• Fossils of species younger than 150mya are
now restricted to separate continents
suggesting that they evolved after the breakup
of the continents from the supercontinent of
Pangea
• Remote islands are often home to endemic
species suggesting that they evolved in
isolation after an ancestor colonized
Galapagos Islands
Galapagos Diversity
Galapagos Finches
Madagascar
Madagascar
Evidence from Anatomy
• Homologous features have similar structures
but may perform very different functions.
• Examples: forelimb of human, whale, cat, bat,
bird…
Evidence from Anatomy
• Embryonic development of many species also
seems to indicate an evolutionary relationship
• http://www.pbs.org/wgbh/nova/evolution/guessembryo.html
(short interactive activity)
• Vestigial features are rudimentary structures that
serve no useful function and are usually taken as
very compelling evidence for evolution. The
explanation is that they must once have served a
function that was beneficial
– Examples: appendix, vestigial tail in humans,
vestigial legs in snakes, whales
Evidence from Artificial Selection
• Through selective breeding humans can
produce dramatic changes in a species
appearance over a relatively short period of
time
Examples: pigeons, broccoli family, dogs
• Nature could have a similar mechanism to
produce change over many generations
Pigeon Breeding
Natural Selection
• How does Natural Selection work?
• https://www.youtube.com/watch?v=xkwRTIK
Xaxg&index=4&list=PL5270149AB732F0FB
(7 min)
• Take your own notes during this video
The Four Processes of
Natural Selection
• Genetic Variation
– There is variation within a species, and most of this
variation is inherited genetically
• Overproduction of Offspring
– Only a few offspring will survive long enough to reproduce
• Struggle for Existence
– There is intense competition for limited resources such as
food, space, and mates
• Differential Survival and Reproduction
– Individuals with advantageous traits will be more likely to
survive and reproduce
– Over time those traits will become more common in the
population
Crash Course Natural Selection
• https://www.khanacademy.org/science/biolog
y/crash-course-biology-science/v/crashcourse-biology-113 (12 min)
• There are some extra terms (such as the types
of selection) in this video you don’t need to
know, but it’s a great summary
• Sit back and enjoy!
Isn’t Evolution Just a Theory?
• Yes it is a Theory. However, a theory in science is
NOT a flimsy guess as it would be in everyday
language. We have to remember the definition of
a Theory in Science:
An explanation or model based on observation,
experimentation, and reasoning, especially one that has
been tested and confirmed as a general principle
helping to explain and predict natural phenomena.
– Video:
(7min)https://www.youtube.com/watch?v=85diEXbJB
Ik&index=1&list=PL5270149AB732F0FB
Why Does Evolution Matter Now?
• An understanding of evolution helps us to
understand and predict how organisms will
change due to changes in the environment.
• This can allow us to react effectively to new
threats and concerns.
Why Does Evolution Matter Now?
– Creating “Super Bugs” such as Multi-Drug
Resistant Tuberculosis (7 min)
• https://www.youtube.com/watch?v=6jBD8xfbf4Y&list=
PL5270149AB732F0FB&index=6
• Antibiotics are a powerful tool against disease, but they
also act as a selection pressure for the bacteria
• Those bacteria that can survive the antibiotics become
more common, and over time the antibiotics won’t
work anymore
• The over use and misuse of antibiotics is causing the
evolution of extremely dangerous strains of diseases
like TB
What can you do?
• Don’t use antibacterial soaps and products!
– This just provides more opportunity for dangerous
bacteria to evolve
• If prescribed antibiotics, follow the directions
carefully!
– If you don’t finish the treatment, then some
bacteria will survive and pass on their genes for
better survival, making the species stronger