1. Evolution Part 1
The Introduction

2. Evolutionary Relationships
Studying fossils has helped scientists understand evolutionary relationships
Fossils are the preserved remains or impressions left by organisms that lived in the past.
The fossil record is the ordered arrangement in which fossils appear within sedimentary rocks.
These rocks record the passing of geological time and provides an actual record of the Earth’s past life forms

3. Geological Time Scale = used to represent evolutionary time
Developed by studying rock layers and fossils worldwide

4. DETERMINING FOSSIL AGE

5. Relative Dating = estimating a fossil’s age compared with that of other fossils
Gives an approximate age of fossils
Law of Superposition: The fossils in the top rock layers are younger than the fossils in the deeper layers of rock
Layer 1
Layer 2
Layer 3
Layer 4

6. Radiometric Dating = calculating the age of a sample based on the amount of remaining radioactive isotopes it contains
Half-life = the length of time required for half of the radioactive atoms in a sample to decay
Example
Original amount of radioactive material
After 1 billion years
After 2 billion years

7. 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) !!!!!!!!

8. 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.

9. 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

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

11. 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

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

13. 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

14. 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

15. 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

16. 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

18. 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

19. 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

20. 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.

21. 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

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

23. 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

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

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

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

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