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Lecture 4
Charles Darwin
- was he a quack?
What is Evolution?
Evolution is technically defined as: "a gradual process
in which something changes into a different and usually
more complex or better form."
As it is most famously used, "evolution" is the process
by which an organism becomes more sophisticated
over time and in response to its environment.
The Theory of Evolution is currently the most popular
concept of how life reached its current state. -Evolution
as a biological mechanism is driven by natural
selection.
This theory is favored by many scientists to explain
phenomena in nature, so much so that it is generally assumed
as factual in most studies.
Definition
Biological evolution, simply put, is
‘descent with modification’ - C. Darwin.
This definition encompasses
small-scale evolution (changes in gene frequency in a
population from one generation to the next) and
large-scale evolution (the descent of different species from a
common ancestor over many generations).
Evolution helps us to understand the history of life.
Biological Evolution
Biological evolution is not simply a matter of
change over time.
Lots of things change over time:
trees lose their leaves
mountain ranges rise and erode,
…but they aren't examples of biological evolution
because they don't involve descent through
genetic inheritance.
The central idea of biological evolution
is that all life on Earth shares a common
ancestor, just as you and your cousins
share a common grandmother.
Through the process of descent with
modification, the common ancestor of
life on Earth gave rise to the fantastic
diversity that we see documented in the
fossil record and around us today.
Evolution means that we're all distant
cousins: humans and oak trees,
hummingbirds and whales.
…and slime moulds, and spiders
Evolution is a science
Sometimes the best way to understand
science is to review the history rather
than understand the logic……
Very early ideas
Cavemen (75,000 B.C. to 10,000 B.C.)
What could they have pondered over?
Ask the Geico Caveman
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Early ideas
550 B.C.
A Greek philosopher, Miletus, argued that
the Earth was not created abruptly
life had started as slime in the oceans
later moved to land
humans and other vertebrates had
descended from fish.
Before Aristotle
454 B.C.
Another Greek philosopher, Empedocles,
speculated that animals developed from
plants
The Universe and all in it is gradually
changing
Aristotle
Aristotle (384 - 322 B.C.)
Suggested that all species are static
All species can be arranged according to
the degree of perfection
Created by God
‘Great Chain of Being’
These ideas went unchallenged until the
17th century in the Western World
John Ray
1627-1705
Classified over 18,000 plants
Proposed the first definition of a species
Maintained that species do not change
He was concerned about the fossil record
evidence emerging at the time!
He is the ‘Father of Botany’
Carl von Linne
Better known by his Latin name - Carolus
Linnaeus (1707 - 1778)
In 1735 he tried to classify all life on Earth, in
order to discover a pattern of the creation
He wanted to classify ‘Man’ in a group alone
but failed to find a scientific reason to do so,
and grouped with other apes.
Acquired characteristics - Biological evolution is gene based
A regular and sustained program of weightlifting yields enlarged muscles, an immediate
physiological response of muscles to the increased effort. However, these big muscles
remain with the individual that endured the regular exercises, and are not passed to their
offspring. This is because the enlarged characteristics result from individual effort, not from
an inheritable genetic change.
Evolutionary predecessors
Over the years before Darwin, many
biologists attempted to solve the
mystery of the “species question.”
Who was
Charles Darwin?
1. Charles Robert Darwin was born in Shrewsbury,
Shropshire, England on 16th Feb 1809
2. His father (Robert Waring Darwin) and grandfather (E.
Darwin) were both doctors
3. His mother was Susannah Wedgewood Darwin was the
daughter of a Josiah Wedgewood - founder of
Wedgewood China
4. He had one brother and four sisters
5. He attended Shrewsbury Grammar School, but preferred
to hunt and collect shells and coins. He also enjoyed
learning Latin and Greek.
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Darwin Family Tree
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 In 1825 he enrolled at Edinburgh University to study medicine,
where he learned about taxidermy (useful later in his life)
 He dropped out because he did not like the classes.
 He had failed his family!!
 In 1827 he enrolled at University of Cambridge and began to
study to become a clergyman
 However, he preferred to collect insects!!!
 It was at Cambridge that he began to appreciate the vast diversity
of species
 His professors were followers of Lamarck’s ideas about
inheritance of acquired characters
 He also learnt natural theology - Understand God by studying
God’s creation
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 Darwin did graduate from Cambridge at age 23 with a B.Sc.
Degree in Theology
 Before joining the Church of England he wanted to travel - as it
was the great time of exploration.
 He wanted to visit exotic locations before settling down to
religious work.
 In 1830, the British government commissioned a 90-foot ship HMS Beagle - devoted to ‘the acquisition of knowledge.’ It was
really to test new clocks and find new sources of wealth.
 Darwin, through a contact at Cambridge, was recommended as
an alternative and signed up as the ship’s unpaid naturalist
 The Beagle sailed more than 40,000 miles from Dec 1831 to Oct
1836
 Darwin spent 18 months at sea and the rest of the time on land
 Of the 58 month voyage, he spent 43 in South America
 He visited the Galapagos Islands where he made his most profound
observations.
 This time would transform his life and biology!
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Galápagos tortoise
 Whilst on the voyage he was given a book to read by the captain - this book
would transform Darwin’s thinking
 The book was written by Lyell, who had put together all the previous arguments
about the age of the Earth and geological time, providing real examples of
geological changes that shaped the planet.
 When Darwin boarded The Beagle he was a firm believer in the clergy and the
fixation of species - when he disembarked he was a changed man and wanted to
discover the laws of nature!
 Then back on England Darwin began to put all the
pieces together….
 Another book that Darwin read, sealed the deal for him…
 A manuscript published by Thomas Malthus implied that given
ideal conditions a population would grow exponentially
 However, the resources would not grow in the same fashion - they
would grow linearly
 Therefore, at some time the population would exceed the
resources and there would be a ‘struggle for existence’
 Darwin put together the short term struggle for existence
(Malthus) with the great geological timescale (Lyell)
Galápagos finches
Analysis of these finches led scientists to hypothesize
that they were derived from one ancestor arriving
from the mainland to populate and diversify across
the islands.
Evidence supporting evolution
The Fossil record
Common Structures
Species Distribution
Developmental Similarities
DNA sequence comparisons
Rock layers
Carbon dating
Common Structures
Man
Pig
Horse
Whale
Bat
Species Distribution
Developmental Similarities
DNA sequence comparisons
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Break
Link to the video clips
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Evolution is not real
Evolution is just a theory!
Watch this clip and answer these questions
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Is a theory just as simple guess?
What is an inference?
What did Darwin infer?
6:06
Darwin’s Dilemma
Watch this clip and try to understand the self
turmoil which he went through
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Which ship did he travel on?
Which idea became clear to him?
What courage did Darwin have?
Where is he buried?
6:36
How does evolution work?
Watch this short video and answer
these questions
http://www.pbs.org/wgbh/evolution/educators/teachstuds/svideos.html
Natural Selection is really composed of
which components?
How is the length of the humming bird
bill determined?
6:41
Did humans evolve?
Watch this short video and tackle these
questions;
What is a common ancestor?
Is it the same as a chimpanzee?
Which species does not have DNA?
How similar is our DNA to chimps?
5:34
Why care about evolution?
Has profound health and welfare issues
Watch and answer these questions
Do bacteria evolve?
How about viruses?
What is the leading infectious killer of
adults today?
6:19
What is controversial about
evolution?
Watch this important clip and digest
What was the evil book?
Must you have to choose between faith
and evolution?
6:34
Religion and Evolution
The late Pope John Paul II said openly that
evolution happened
Many very orthodox people refuse to accept
evolution at all
Scientists base their theories on evidence that
can be tested - evolution is a very solid theory at
this time
Many religious commentators attack single
aspects of the evolution theory
It is Religion which cannot be tested in this
manner, as we first need evidence to begin
Ken Ham
Watch this clip of Ken Ham - a biblical literalist
http://www.pbs.org/wgbh/evolution/library/08/1/real/l_081_04.html
What is his angle on evolution?
What proof does he provide for his views?
How does he explain the finding of fossils?
What is questionable with his interpretation?
6:06