1. EQ: How does natural selection relate to evolution?1

2. After Cambridge, Charles was recommended for a surveying trip on the HMS Beagle.
Darwin sailed around the world on the Beagle for 5 years, working as a naturalist. 3

3. Darwin made many observations and collected evidence on his voyage that led to his theory about the way life changes. 4

4. At the time Darwin made his trip, the majority of people believed the Earth and all of its forms of life had been created only a few thousand years in the past. 5

5. People also believed that the Earth had not changed during those few thousand years.
People also believed in fixity of species; in other words, species never changed.
After careful observation and study of new scientific discoveries, Darwin began to think otherwise.
Photo from original manuscript of William Buckland
The first dinosaur to be described scientifically was Megalosaurus by William Buckland in 1824. 6 6

6. The Father of Geology
Darwin was influenced by geologist James Hutton’s writings that described geologic forces he thought had changed and were still changing the earth.
Hutton proposed that the Earth had to be much more than a few thousand years old. 7

7. Darwin was also influenced by geologist Charles Lyell who wrote Principia Geologica.
Lyell’s book proposed that tremendous geologic processes had shaped the Earth such as seen in volcanoes active in the present. 8

8. On the voyage, Darwin noticed that everywhere he went, the animals and plants differed vastly.
Patterns in the species suggested that the species had changed over time and had given rise to new and different species. 9

9. “Galapagos” means turtle.
Many of Darwin’s conclusions were based on observations of wildlife in the Galapagos Islands.
The Galapagos Islands lie 500 miles west of Ecuador in the Pacific Ocean, directly on the equator.
“Galapagos” means turtle. 10

10. Galapagos finches
Darwin noticed on these islands, there were several types of finches.
What it must have been like to be Darwin… 11

11. Galapagos finches
In particular, Darwin observed something odd about the finches: they all looked like a bird he had seen on the South American continent. 12

12. Darwin wondered if the birds and other animals had been created to match their environment, why didn’t these birds look like the birds of the African continent, since the environments of both the Galapagos and Africa were similar. 13

13. Once on the islands, the birds must have changed over the years.
Darwin guessed that some of the birds from South America migrated to the Galapagos.
Once on the islands, the birds must have changed over the years. 14

14. This would explain the numerous species of birds present.
large ground finch
woodpecker finch
cactus finch
This would explain the numerous species of birds present. 15

15. Descent With Modifications
Darwin concluded:
Each species has descended, with changes, from other species over time.
Darwin called this…
Descent With Modifications or
evolution
(change in species over time) 16

16. People have more children than are able to survive.
Darwin based his theory on his own observations and the writings of Thomas Malthus.
Malthus was a British social scientist who proposed theories on factors controlling population growth:
People have more children than are able to survive.
There are built-in population checks: disease, famine, and war. 17

17. …or Survival of the Fittest.
Darwin extended these principles to biology, which helped him form his theory of…
Natural Selection
…or Survival of the Fittest. 18

18. On the Origin of Species
Natural selection was the mechanism by which Darwin proposed that evolution took place.
Darwin published his theory in the book
On the Origin of Species 19

19. Five basic components of
Natural Selection 20

20. 1. All species have genetic variation.
Every species is different, even within itself.
Variation is caused by mutations and meiosis. 21

21. 2. Organisms produce more offspring than the amount that actually survive.
The female green sea turtle lays a clutch of about 110 eggs. She may lay several clutches.
It is likely that less than 1% of the hatchlings will ever reach sexual maturity. 22

22. Competition exists WITHIN and AMONG species.
3. Since more organisms are produced than can survive, there is competition (struggle for existence).
Competition exists WITHIN and AMONG species.
Within and Among Species for
food
water
shelter
space
And Within a Species for
mates 23

23. The constant struggle for survival is affected by short-term natural disasters. (drought, fires, floods, snowstorms, hurricanes, and tornadoes)
Mineral Management Service photo courtesy of GeekPhilospher.com
The constant struggle for survival is also affected by long-term changes in the environment. (ice ages, biome shifts, etc) 24 24

24. He who spreads the most genes wins!
4. Survival of the fittest Some organisms are more suited to their environment as a result of variations in the species.
Fitness: the ability of an individual to survive and reproduce in its specific environment. Fitness is a result of adaptations.
Individuals that are fit to their environment survive and leave more offspring than those who aren’t.
He who spreads the most genes wins!
1st 25

25. Characteristics of fit individuals increase in a population over time.
5. Descent with modification: Living species today are descended with modifications from common ancestral species that lived in the past.
Characteristics of fit individuals increase in a population over time.
Over time, genes for less favored characteristics will be eliminated from the gene pool.
Example: giraffes and their increasingly longer necks. 26

26. Natural Selection: Survival of the Fittest
An adaptation is any inherited characteristic (a genetic variation) that can increase an organism’s chance of survival.
An organism does not change because of need or desire to survive. The organism either already has the variation that enables it to survive or it dies.
a. the variation exists first.
b. the environment changes.
c. a variation may give an advantage to survive environmental change. 27

27. Artificial Selection
Nature provided the variation but humans selected those variations that they found useful (selective breeding)
Ex: wild strawberry vs. domesticated strawberry, domestic dogs 28