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Descent with Modification
By Natural Selection
Darwin’s influences

Carolus Linnaeus (1707-1778)- Developed a classification system for all
known organisms.

Georges Cuvier (1769-1832)- Studied fossils near Paris. Noted differences
between strata. Opposed to ideas of evolution

James Hutton (1726-1797) & Charles Lyell (1797-1875)- Both were
geologists that suggested that the Earth’s geologic features could be
explained by gradual mechanism’s that occurred in the past and were
ongoing.
Hutton and Lyell’s ideas about geological processes were critical.
Provided physical evidence that the Earth was older than the common thinking
of the day.
This was essential to Darwin’s ideas that change was gradual. Origin of new
species under Darwin’s theory would take millions of years NOT a few
thousand.
Another theory


Jean-Baptiste de Lamarck ( 1744-1829)

Use and disuse

Inheritance of acquired characteristics
Suggested that changes in organisms were purposeful. That they desired to
be more complex. If you used a body part more, it became larger and
stronger. You could then pass this trait to offspring.

Example- Giraffe stretches his neck
Darwin was NOT influenced by

Gregor Mendel (1822-1884)

While they were basically contemporaries, Darwin knew nothing of
Mendel’s pea plant experiments.

He had no idea about the mechanism of inheritance.
Darwin’s Question
 Could
a new species arise from an ancestral
form by gradual accumulation of adaptations?
Two observations
1.
Members of a population often vary in their inherited traits.
2. All species can produce more offspring than their environment can support
and many of these fail to survive and reproduce.
Two inferences
1.
Individuals whose inherited traits give them a higher probability of
surviving and therefore reproduce in a given environment tend to leave
more offspring.
2.
This unequal ability of individuals to survive and reproduce will lead to the
accumulation of favorable traits in the population over generations.
Four parts of Natural Selection

Inherited variation

Overpopulation

Struggle to survive

Successful reproduction
Natural selection
A
process in which individuals that have certain
inherited traits tend to survive and reproduce
at a higher rate because of these traits.
An example of natural selection
 The
peppered moth
The Industrial Revolution

Factories

Soot covered trees

Lichens dying off
Which is more likely to survive?
What if the factories clean up their act?
Important things to know

Environments change and act as selective mechanisms on populations

Variations are not directed by the environment but occur randomly

Some variations increase or decrease fitness of an organism to its
environment.

Those organisms that are more “fit” will tend to survive, reproduce, and
pass those desirable traits on

Humans can impact variation in other species
Now, which is likely to survive?
Descent with Modification by Natural
Selection Explains:

The unity of life

The diversity of life

The match between organisms and their environments

On my web site you will find the following link:
http://evolution.berkeley.edu/evolibrary/article/fireants_01

Please open it and read about the evolution of Fire Ants
Homework

Below are some examples of natural selection in action. Pick 1 to research
and describe in 100 words or fewer. (Total word count)

Lactose tolerance/ intolerance

Nylon eating bacteria

Methicillin- resistant Staphylococcus aureus (MRSA)

DUE THURSDAY 12/3