1. CORNELL NOTES: CHARLES DARWIN & NATURAL SELECTION
EQ: How do the traits in populations change over time through natural selection?
CORNELL NOTES: CHARLES DARWIN & NATURAL SELECTION

2. Evolution
When Populations of living things slowly adapt and change over time
Does not explain origin of life

3. Evolution theory is a way to show the connection of all life forms

4. Evolution also explains the variety within a kind
Ex. Types of cats

5. Jean Baptiste Lamarck 1744-1829
Evolution through acquired traits
Based on fossils, relics or impressions of dead organisms
Sedimentary rock, ice, tar, amber

6. Charles Darwin 1809-1882 Evolution by natural selection
Also cited fossil evidence
Anticipated that intermediates
would be found
Travelled extensively to
observe diversity of life
Published “origin of species”
In 1859

7. Lamarck
Individual organisms change. These changes are passed on to offspring
Ex Giraffes – stretched their necks to get food and passed longer necks on to offspring

8. Darwin Said species change by
Natural Selection. Survival of the fittest.
The ones best naturally adapted to survive, have more offspring and pass on the traits to those offspring

9. Darwin’s version of giraffes
Some giraffes were born with longer necks and better able to get food. These ones survived and passed longer necks to their offspring

10. Darwin’s big adventure!
He sailed around the world

11. Galapagos islands
Darwin’s most famous observations

12. He studied lots of interesting creatures in Galapagos
seals, tortoises, iguanas and blue footed boobies

13. Factors Required for Natural Selection
1. Genetic variations in the population
2. competition (more organisms are produced than survive)
3. Some genetic variations are favorable
4. Favorable variations will allow for survival
5. A population will change over time.

14. Especially finches

15. Darwin’s Finches Finches on different islands developed
type beaks due to
natural selection
according to type
of food available.
better beaks survived
better

16. Comparison summary
Lamarck – individual changes to adapt to environment. Passes changes to offspring
Darwin – Certain individuals born with advantages, and passes them to offspring Changes due to random variation and mutation

17. Darwin or Lamarck?
A sea turtle that has more webbing on its feet can swim better and catch more food and survives to have lots of offspring
Darwin

18. Darwin or Lamarck?
A rabbit living in arctic has a lighter color coat and hides better from the wolf, survives to have offspring better
Darwin

19. Darwin or Lamarck?
A squirrel grows longer claws to grab tree branches better to keep from falling and when it has offspring, they are born with longer claws to grab branches
Lamarck

20. Similarities of Darwin and Lamarck
Both Darwin and Lamarck believed changes were due to environmental pressure and changes (lack of food, shelter, mates etc)

21. Descent with modification
Slight changes can occur from one generation to the next
Called gradualism
Punctuated equilibrium – Changes occur suddenly (an alternate model that explains lacking fossil evidence)

22. Which organism is more fit now?
Originally, the vast majority of peppered moths were light-colored, which effectively camouflaged them against the light-colored trees and lichens in which they rested upon. However, because of widespread pollution during the Industrial Revolution in England, many of the lichens died out, and the trees that peppered moths rested on became blackened by soot.
What effect do you think this had on the population of light colored peppered moths? Why? What about the dark colored peppered moths?
What is the variation in this population?
Which variation is more favorable?
Which variation will allow for survival?
Which organism is more fit now?
How will the population of peppered moths change over time?
Peppered Moth Simulation

23. Natural selection
A differential success in reproduction caused by an interaction between the environment and the
phenotypes of a population
Environment selects
for favorable traits