2. Charles Darwin (1809-1882) Sailed around the world 1831-1836

3. What did Darwin’s Travels reveal
The diversity of living species was far greater than anyone had previously known!!
These observations led him to develop the theory of evolution!!

4. How did tortoises and birds differ among the islands of the Galapagos?
Each island had its own type of tortoises and birds that were clearly different from other islands

5. Galapagos Turtles

6. Evolution is when organisms change over time
Evolution is when organisms change over time. So, modern organisms descended from ancient ones

7. Malthus
Reasoned that if the human population continued to grow unchecked, sooner or later there would be insufficient living space and food for everyone

9. Darwin finally published his ideas in 1859
Other naturalists were developing the same theory that Darwin did.
Even though he was afraid of the Church’s reaction to his book he wanted to get credit for his work.

10. Artificial Selection
nature provides variation, humans select variations that are useful.
Example - a farmer breeds only his best livestock

11. Natural Selection
The traits that help an organism survive in a particular environment are “selected” in natural selection

15. Natural Selection and Species Fitness
Overtime, natural selection results in changes in the inherited characteristics of a population.
These changes increase a species fitness (survival rate)

17. Descent with Modification
Each living species has descended with changes from other species over time

18. Summary of Darwin’s Theory
1. Organisms differ; variation is inherited
2. Organisms produce more offspring than survive
3. Organisms compete for resources
4. Organisms with advantages survive to pass those advantages to their children
5. Species alive today are descended with modifications from common ancestors

20. Natural Selection Does not act directly on genes, but on phenotypes
Affects which individuals having different phenotypes survive and reproduce and which do not.
Reproducing individuals add to the population
Non-reproducing individuals die without passing on their genetic material (genes).

21. Types of Natural Selection
SBI 4U: Metablic Processes
Types of Natural Selection
Directional selection – The environment favours individuals with an extreme variation of a trait.
Occurs when organism moves to a new environment
ex. gill nets and salmon fishing in 50s and 60s
Gill nets in the 1050s were made of hemp and had larger mesh size (e.g. only catching larger fish) therefore large fish (an extreme variation of a trait) were selected against while average – smaller sized fish were able to swim through and survive
Section 1.3

22. Types of Natural Selection
Stabilizing selection – the extremes of a population are selected against and the average is favored.
Once well adapted to environment, selection pressures tend to prevent them from changing
ex. baby weights (3kg)

23. Types of Natural Selection
Disruptive selection – selects for extremes and against the average.

24. SBI 4U: Metablic Processes
Disruptive selection
Taste good
Taste bad
Section 1.3

26. Sexual selection Favours the trait that influences mating success
Usually based on female choice and/or male vs. male competition
Male competition
Male competes against other males for territory, or access to females
Anything that gives him an advantage makes him more likely to pass on his genes

27. SBI 4U: Metablic Processes
Female selection (or male selection)
Leads to sexual dimorphism (physical differences between males and females)
Male must prove he is genetically good enough
Plumage, gifts, nesting site or mating rituals
Selection makes many organisms go to extreme lengths for sex: peacocks (top left) maintain elaborate tails, elephant seals (top right) fight over territories, fruit flies perform dances, and some species deliver persuasive gifts.
Section 1.3