Basics of Natural Selection Topic 3035

1
Basics of Natural Selection Topic 3035

• By Jonathan Edgerly

2
The Father of Natural Selection and Evolution

• Darwin
• Darwins Theory has four main parts
• 1.) The physiology of an organism is constantly
  changing. The organisms that are around today
  werent around in the past.
• 2.) All organisms are derived from common
  ancestors by a process of branching

3
The Father of Natural Selection and Evolution
cont.

• 3.) Change is gradual and slow, taking place
  over a long period of time.
• 4.) The mechanism of evolutionary change is
  Natural Selection.

4
The Process of Natural Selection

• If all the offspring that organisms can produce
  were to survive and reproduce, they would soon
  overrun the earth.
• "The elephant begins breeding at 30 years old and
  goes on breeding until 90 years oldafter a
  period from 740 to 750 years there would be
  nearly 19 million elephants descended from this
  first pair."
• -Charles Darwin

5
The Process of Natural Selection

• Offspring tend to resemble their parents. This
  includes characteristics that influence an
  individuals success in surviving and
  reproducing.
• Parents possessing certain traits that enable
  them to survive and reproduce will pass on these
  traits to the next generation of offspring.

6
The Process of Natural Selection
7
Natural Selection Requirements

• There must be heritable variation for some trait.
  
• Examples beak size, color pattern, thickness of
  skin, fleetness
• There must be an increased chance of survival and
  reproduction due to the possession of a
  particular trait.
• Example moth coloring, camouflage coloring

8
Examples

• Some plants genetically grow taller more quickly
  allowing them to reach out of under story.
• Some individuals are faster runners than others.
  
• But if speed gap between prey and predator is
  large it would not matter (e.g. if cheetahs ate
  snails).

9
Evidence of Natural Selection
During the Industrial Revolution, soot and other
industrial wastes darkened tree trunks and killed
off lichens. The light-colored morph of the moth
became rare and the dark morph became abundant.
In 1819, the first melanic morph was seen by
1886, it was far more common -- illustrating
rapid evolutionary change.
http//www.sprl.umich.edu/GCL/Notes-1999-Fall/sele
ction.html
10
Summary

• Darwin's theory of evolution drastically changed
  the direction of future scientific thought,
  though his theory was built on a growing body of
  thought that began to question prior ideas about
  the natural world.
• Darwin's theory of natural selection is a
  continuous process that occurs over successive
  generations.

11
Summary cont..

• Natural selection requires heritable variation in
  a given trait and differential survival and
  reproduction associated with possession of that
  trait.
• Examples of natural selection are
  well-documented, both by observation and through
  the fossil record.