1. Natural Selection and Adaptation
Because the environment is always changing, there is no perfectly-adapted organism.
There are three preconditions for natural selection:
a. The members of a population have variations that can be passed on.
b. Overpopulation = more individuals are produced each generation than the environment can support.
c. Some individuals have adaptations that allow them to survive and reproduce better than others

2. There are two consequences of natural selection.
a. An increasing number of individuals in future generations will have the adaptations.
b. A population becomes adapted to its local environment.

3. Natural selection can only use variations that are randomly provided; therefore there is no directedness or anticipation of future needs.
Extinction occurs when 
previous adaptations are no
 longer suitable to a changed 
environment.

4. Organisms Have Variations
1. variations are essential in natural selection (before looked at as imperfections)
2. variation is completely random.
3. New variations can be harmful or helpful.
4. Variations that make adaptation possible are those that are passed on from generation to generation.
5. Darwin could not state the cause of variations because genetics was not yet established.

5. ORGANISMS DIFFER IN FITNESS
FITNESS is a measure of an organism’s reproductive success
Reproduction is important for evolution, only those who survive to reproduce, pass on those advantageous genes.

6. Organisms Become Adapted
An adaptation is a trait that helps an organism be more suited to its environment. 
2. This is recognizable when unrelated organisms living in a particular environment often display similar characteristics.

7. Evidence for Evolution
Evidence supports common descent.
Fossils Evidence
Biogeographical Evidence
Anatomical Evidence
Biochemical Evidence

8. Evidence for Evolution: Fossil Record
Fossil evidence
Fossils record the history of life from the past
Documents a succession of life forms from the simple to the more complex
Sometimes the fossil record is complete enough to show descent from an ancestor
Transitional fossils are a common ancestor for two different groups of organisms
It allows to trace the descent of organisms

9. Evidence for Evolution: Biogeographical
Distributions of plants and animals across earth
Consistent with origin in one locale and then spread to accessible regions
Hypothesis that different mix of plants and animals would be expected whenever
Geography separates:
Continents, islands, seas, mountains, and so on.

10. Evidence for Evolution: Anatomical
Vertebrate forelimbs:
Homologous - All contain the same sets of bones in similar ways
Yet they are modified extensively to meet various adaptive needs
Darwin interpreted this as support for a hypothesis of common descent
Embryological development
All vertebrate embryos have:
A postanal tail and
Paired pharyngeal (gill) pouches

11. The Evidence of Evolution: Anatomical
Homologous Structures:
Anatomically similar because they are inherited from a common ancestor
May be functionally similar or not
Analogous Structures:
Serve the same function
Not constructed similarly
Do not share a common ancestor
Vestigal Structures:
Fully-developed anatomical structures
Reduced or obsolete function

12. Significance of Homologous Structures
bird
humerus
ulna
radius
metacarpals
phalanges
bat
whale
cat
horse
human

13. Significance of Developmental Similarities
fish O f r o m a i r
salamander
tortoise
chick
pharyngeal
pouches
human
postanal
tail

14. Biochemical Evidence Almost all living organisms:
Use the same basic biochemical molecules
Utilize same DNA triplet code
Utilize same 20 amino acids in their proteins
DNA base-sequence differences:
When very similar, suggest recent common descent
When more different, suggest more ancient common descent

15. Significance of Biochemical Differences
yeast
moth
fish
turtle
duck
pig
monkey
human 10 20
Number of Amino Acid Differences
Compared to Human Cytochrome c 30
Cytochrome c is a small protein
that plays an important role
in the electron transport chain
within mitochondria of all cells 40 50