Unit 5 - Evidence For Evolution

Question 1

Paleontology

Answer 1

The study of the fossil record.

Scattered throughout the world => Clarkia, Vantage, Burgess Shale

Question 2

Fossil formation

Answer 2

For this to occur, two processes must be avoided: decomposition and scavenging. Rapid burial or encasement of organisms facilitates fossil formation => amber, tar pits.

Most fossils are formed by:
1. Decay Resistant Structures (bones, shells)

2. Typically in Sedimentary Rock (typically forms in aquatic environments)

Question 3

Dating fossils (2 ways)

Answer 3

1. Relative Dating
   - Attempt to assign a chronological age: oldest to youngest.
   a. Superposition - Done in undisturbed sedimentary deposits.
   b. Fossil Correlation - Use index fossils to date strata. Rocks with similar fossils are similar in age. This contributed to the geologic time scale.
2. Absolute Dating
   - Attempt to assign a real age by using radioisotopes.
   a. Half life - time required to change 1/2 parent element into a daughter element.

Question 4

Difficulties With Absolute Dating

Answer 4

1. Erosion of parent/daughter
   - This leads to artificially old or young dates.
   - erode parent out = artificially old
   - erode daughter in = artificially young
   
   • assume closed system
2. Igneous works best
   - it contains the radioisotopes involved, but no fossils. So we correlate igneous deposits with sediment deposits.
3. Assume initial ratio
   - Starting conditions of parent : daughter

Question 5

Basis of Paleontoloty

Answer 5

The present is key to the past

backwards expiramental method

Question 6

Scientific validity of paleontology

Answer 6

1. Historical Reconstruction
   - Science should be repeatable, history is not
2. Hypothesis Characteristics
   - Must be testable and capable of falsification
3. Sample Size - Often limited in the fossil record which prevents use of inferential statistics
4. Interpretation - If a bone fragment is identified as an occipital bone, the curvature is used to extrapolate cranial volume

Question 7

Cambrium Explosion

Answer 7

The “rapid” appearance of all major phyla during cambrium time period (540 mya). No new phyla since. Biological Big Bang.

Question 8

Biogeography

Answer 8

The biological distribution of life forms on earth. Organisms in similar environments have similar adaptations.
=> placental vs marsupial

Question 9

Embryology Recapitulates Phylogeny

Answer 9

Development Retraces Evolutionary Relationships. Discredited

Question 10

Homologous Structures

Answer 10

Structural similarity but functional diversity. Suggests common ancestry.

Question 11

Vestigial Structures

Answer 11

These have no known function, which suggests common ancestry. => pelvic girdle in whales.

Human Examples - appendix (actually immune role), tonsils (immune), tailbone, body hair.

Original List of 186 - vein valves, pineal glands, tear glands.

Question 12

Molecular Evolution

Answer 12

DNA w/ universal codons
suggests common ancestry

ATP - energy transfer molecule.
suggests common ancestry.

Proteins - related organisms have higher similarity in protein sequences.

Question 13

Mitochondrial DNA
Inheritance?
Changes?
Placental analysis?

Answer 13

Inheritance - Only from mother due to unequal cytokinesis during oogenesis. Only passed on by daughters.

Changes in mtDNA - only by mutation. clock mechanism

Placental Analysis - Berkeley Study: gene analysis of mtDNA in 147 placentas revealed a common female to all members. Mitochondrial “Eve” is estimated to live 200,000 years ago.