2. Charles Robert Darwin
Charles Darwin was born in England on February
12, 1809
After graduating from the best school at
Shrewsbury in 1825, Darwin went to the
University of Edinburgh to study medicine.
In 1827 he dropped out of medical school and
entered the University of Cambridge.
5. Charles Robert Darwin
In 1831, he joined a 5 year scientific expedition on the survey
ship HMS Beagle as their geologist.
6. Charles Robert Darwin
The idea of evolution has been around for a long time (even
before Darwin)
7. Charles Robert Darwin
Darwin read a book called “Principles of Geology” by Charles
Lyell on the Beagle
8. Charles Robert Darwin
Lyell suggested that the fossils found in rocks were actually
evidence of animals that had lived many thousands or millions of
years ago.
Lyell's argument was reinforced in Darwin's own mind by the
rich variety of animal life and the geological features he saw
during his voyage.
9. Charles Robert Darwin
Darwin noticed that each island supported its own form of finch
which were closely related but differed in important ways.
10. Charles Robert Darwin
Darwin found that the shapes of tortoise shells corresponded
to different habitats.
12. Charles Robert Darwin
Another scholar of the time, Thomas Malthus, studied populations
and had a great impact on Darwin’s understanding of finches,
other organisms, and his theory of evolution.
Malthus believed that given unlimited resources, a population would
grow exponentially.
Under normal conditions, a natural population would be limited by
food, water, habitat, etc. resulting in a balancing of population
numbers.
Influenced by the ideas of Malthus, Darwin
proposed a theory of evolution occurring
by the process of natural selection.
13.
14. Charles Robert Darwin
Survival of the fittest
The animals (or plants) best suited to their environment are
more likely to survive and reproduce, passing on the
characteristics which helped them survive to their offspring.
Gradually, the species changes over time.
15. Charles Robert Darwin
Darwin worked on his theory for 20 years.
After learning that another naturalist, Alfred Russel Wallace
had developed similar ideas
the two made a joint announcement of their
discovery in 1858.
16. Charles Robert Darwin
In 1859 Darwin published :
‘ The Origin of Species ‘ by Means of Natural Selection
17. Evolution
Change over time
Occurs to species, not individual
Explains diversity on Earth today
Great variety of types of living things
Between species 10 – 100 million species on earth
How Evolution Works :
Explained by Charles Darwin and Alfred Russell
Wallace Darwin wrote On the Origin of Species
21. How Evolution Works
3. Variation
• Differences among individuals a result of genetic mutation –
changes in DNA
22. How Evolution Works
4. Adaptation
some variation gives some individuals a slight
survival advantage these are favorable traits
traits or characteristics that help an organism
survive in its ecosystem
three types:
29. Genetic Drift
A population bottleneck :
is a sharp reduction in the size of a population due to
environmental events such as:
(earthquakes, floods, fires, disease, or droughts)
30. Genetic Drift
B Founder effect : is the loss of genetic variation that occurs
when a new population is formed by a very small number of individuals
from a larger population
It was first fully outlined by Ernst Mayr in 1942
34. Natural Selection
That results in the adaptation of an organism
to its environment
Determines the traits that allow organism to multiply
and survive
Evolution often occurs as a result of this process
35. Evidences of Evolution
The Fossil Record
Comparative anatomy
Embryonic Development
Vestigial organs
Molecular biology
45. Types of Evolution
Divergent Evolution
• Organisms have a common ancestor
• Changes in environment cause them to adapt
• So they may look/ act differently, but they are still related!
46. Types of Evolution
Convergent Evolution
• Organisms have similar features
• However, they don’t have a common ancestor!
• So they may look/ act the same, but they are not related!
47. Types of Evolution
Convergent Evolution
• Organisms have similar features
• However, they don’t have a common ancestor!
• So they may look/ act the same, but they are not related!
48. Speciation
The most widely accepted definition: A species
is a group of individuals capable of interbreeding to produce
fertile offspring
it has a problem : Hybrid Infertility
Horse X Donkey = Mule
(Cannot Reproduce and produce Fertile offspring)
49. Speciation
So a better definition of a species might be:
A group of individuals capable of interbreeding to
produce offspring that are fertile and these offspring, in
turn, can produce offspring that are fertile.
The process by which new species develop from the
existing species is known as : Speciation.
53. Microevolution
Moths :
• At the beginning of the Industrial Revolution in England, coal burning
produced soot that covered the countryside in many areas
55. Microevolution
White moths became easier to see, while the black moths became harder to see.
The black moths were more likely to survive and pass on the gene for
dark color to their offspring
Over time, the black moths have become more common
