1. EVOLUTION

2. Variation
The differences between individual members of a population (ex: fur color, eye color, etc.)
Can not always be observed
Are almost always genetically inherited
Results from mutations and recombination

3. Adaptation
An inherited trait that increases the population’s chances of survival and reproduction
It can be physical or behavioral

4. Evolution Defined as “change over time”
There were 3 scientists who made important contributions to this field:
Charles Bonnet
Jean-Baptiste Lamarck
Charles Darwin

5. Charles Bonnet Noticed that fossils didn’t look like modern organisms
Theorized that periodic catastrophes affected the entire planet and after each catastrophe life began anew

6. Jean-Baptiste Lamarck
Challenged Bonnet’s views
Believed that the fossils of extinct animals were the ancestors of those living today
Developed Lamarck’s hypothesis

7. Lamarck’s Hypothesis Organisms strive to improve themselves
Principle of Use and Disuse: the most-used body structures develop, whereas unused structures waste away
Principle of Inheritance of Acquired Characteristics: modified structure is inherited by the organism’s offspring**
**This 3rd principle was disproved by August Weismann. Changes in an individual during its lifetime do not affect its reproductive cells or its offspring.

8. Charles Darwin
Scientist who studied plants and animals while on an around-the-world trip
After studying several organisms, he developed his theory of evolution—Natural Selection

9. Natural Selection There is variation within populations
Some variations are favorable [favorable variations improve an organism’s ability to function and reproduce in its own particular environment]
Not all young produced in each generation can survive
Individuals that survive and reproduce are those with favorable variations

10. Rate of Evolution Gradualism: Punctuated Equilibrium:
states that evolution occurs at a slow, gradual rate
this is what Darwin believed
Punctuated Equilibrium:
states that populations remain genetically stable for long periods of time, interrupted by brief periods of rapid genetic change
this new theory was first stated by Stephen Jay Gould and Niles Eldridge

11. Comparing Anatomy Homologous Structures:
structure or characteristic with similar functions found in different species
thought to be inherited from common ancestors
EX: humans, whales, and bats all have the same number and type of bones in the forelimbs

12. Comparing Anatomy (cont.)
Analogous Structures:
structures that are similar in function, but are not inherited from a common ancestor
EX: wings of insects and wings of birds

13. Comparing Anatomy (cont.)
Vestigial Structures:
structures that are inherited, but reduced in size and often unused
suggest structures of the ancestors of modern organisms
EX: pythons have vestigial hip and leg bones

14. Types of Evolution There are 5 different types of evolution:
Speciation
Divergent Evolution
Convergent Evolution
Coevolution
Adaptive Radiation

15. Speciation
new species
species
original species

16. Divergent Evolution
new species
species
new species

17. Convergent Evolution species new species new species species
These two succulent plant genera, Euphorbia and Astrophytum, are only distantly related, but have independently converged on a very similar body form.
These 2 new species share many traits.

18. Coevolution species original species with new traits
Bumblebees and the flowers they pollinate have coevolved so that both have become dependent on each other for survival
species
original species
with new traits

19. Adaptive Radiation new species new species species new species

20. Population Genetics
Populations are the smallest unit in which evolution takes place
Population genetics is the study of genetic traits and changes in populations

21. Hardy-Weinberg Principle
If a population is not evolving, the allele frequencies in the population remain stable
The population is said to be in genetic equilibrium

22. Conditions Required to Maintain Equilibrium
No natural selection
Random mating
No migration
No mutation
Very large population size

23. Types of Selection
In stabilizing selection, the extreme phenotypes are selected against

24. Types of Selection (cont.)
In directional selection, there is a shift in frequency to an extreme phenotype

25. Types of Selection (cont.)
In disruptive selection, the most common variation in a population is not favored