1. Evolution Part 1
The Introduction

2. Evolution
The processes that has transformed life on earth from its earliest forms to the vast diversity that characterizes it today.
Driven by mutations - changes in the genes (DNA) !!!!!!!!

3. Definitions
Evolution is the slow, gradual change in a population of organisms over time
Adaptation is any inherited characteristic that increases the survival and reproductive success.

4. Lamarck’s Theory of Evolution
Jean-Baptiste Lamarck, 1809
One Of First Scientists To Understand That Change Occurs Over Time
Stated that changes are adaptations to an environment acquired in an organism’s lifetime
These acquired changes are passed to offspring

5. Lamarck’s Theory of Evolution
Example: Ducks spreading their toes wide to avoid sinking into mud over time develop webbed feet.

6. Lamarck’s Theory of Evolution
Idea called Law of Use and Disuse
If a body part was used, it got stronger
If body part was NOT used, it deteriorated

7. Lamarck’s Theory of Evolution
Proposed That By Selective Use Or Disuse Of Organs, Organisms Acquired Or Lost Certain Traits During Their Lifetime
These Traits Could Then Be Passed On To Their Offspring
Over Time This Led To New Species

8. Lamarck’s Mistakes
Lamarck Did NOT Know how traits were inherited (Traits are passed through genes)
Genes Are NOT Changed By Activities In Life
Change Through Mutations Occurs Before An Organism Is Born
A mutation is a change in DNA that is the source of new traits that might be an adaptation for an organism

9. Voyage of the Beagle Charles Darwin Born Feb. 12, 1809
Joined Crew of HMS Beagle, 1831
Naturalist
5 Year Voyage around world
Avid Collector of Flora & Fauna
Astounded By Variety of Life

10. The Galapagos Islands Very Different Climates
Small Group of Islands 1000 km West of South America
Very Different Climates
Animals On Islands Unique
Tortoises
Iguanas
Finches

11. Darwin’s Observations
Tortoises - Each island had long or short neck tortoises
Finches - More types appeared on the islands where the available food was different (seeds, nuts, berries, insects…)
Finches had different types of beaks adapted to their type of food gathering

13. Charles Darwin
In 1859 wrote : “On the Origin of Species by Means of Natural Selection”
Two main points:
1. Species were not created in their present form, but evolved from ancestral species.
2. Proposed a mechanism for evolution: NATURAL SELECTION

14. Natural Selection
Natural selection - the overall process by which organisms with better adaptations for their environment survive and reproduce. “Survival of the fittest”
Individuals with favorable traits are more likely to leave more offspring better suited for their environment.
no two individuals are exactly alike

15. Natural Selection
Developed independently by both Charles Darwin and Alfred Wallace,
claims that only organisms with the necessary survival characteristics will be alive long enough to pass on their traits to offspring.
In this way, over time the weakest organisms will be weeded out of a population.

16. Darwin’s Conclusions
1. Individuals in a population have variation. They differ from one another
2. Variations are inherited from parents
3. Populations produce more offspring than can survive. This creates competition
4. Individuals who inherit characteristics most fit for their environment are likely to leave more offspring than less fit individuals

17. Types of Natural Selection
1. Sexual Selection
2. Disruptive Selection
3. Stabilizing Selection
4. Directional Selection

18. Sexual Selection
Traits are increased or decreased in a population due to mate choice
Usually the female does the choosing
Males need to
Be more attractive
Provide shelter for young
Fight for feminine approval

19. Disruptive Selection
Natural selection is favoring two extremes of a trait
Leads to two new species after a LONG period of time

20. Stabilizing Selection
Natural Selection is favoring the intermediate (heterozygote) trait

21. Directional Selection
Natural selection is favoring one extreme of the trait

22. Homework
Evolution Part 1 Notes - Notes Assignment #4