A. Major ideas in physics (cosmology)

1. round Earth - Aristotle, 340 B.C.
2. geometric model - Aristotle, Ptolomy
3. heliocentric model - Copernicous, Kepler, Galileo
4. gravity - Issac Newton
a. Philosphiae Nuteralis Principa Mathematica (1687) - "probably the most important single work ever published in the phiscal sciences" S. Hawking
b. every body in the universe is attracted by a force that is stronger the more massive the bodies and the close they are to each other
c. explains orbits of planets, moons
d. explains why tings fall to the ground
e. space is not absolute - this follows from Newton's laws
5. relativity - Albert Einstein
a. developed in early 1900's
- spacial relativity (1905)
- general relativity (1915; accounts for gravity)
b. revised Newton's ideas
c. time is not absolute (it is relative to position and speed of the observer)
d. time and space are not completely independent; rather they form an object called space-time
e. gravity exists because space-time is not flat; it is curved by the distribution of mass and energy
f. E=mc²
6. quantum mechanics (early 1900's)
a. mostly deals with physics processes at the subatomic level
b. leptons - electrons, etc.
c. quarks - particles that make up protons and neutrons
7. forces
a. gravity
b. strong nuclear force - holds quarks together
c. electromagnetism - holds electrons around nucleus; also responsible for radio and light waves
d. weak nuclear force - causes radioactive decay
8. unification - attempts to find a single law that explains the way the universe works through unification of ideas from general relativity and quantum mechanics; a single mathematical explaination for all four forces

B. Big Bang

1. The universe is estimated to be 10-20 billion years old.
2. The universe is expanding today.
3. All matter, energy, time started at one point and burst outward.
4. Earth and our solar system formed about 4.6 billion years ago.

C. Formation of Earth

1. probably formed through accretion of large rocks
2. center became molten due to pressure and radioactive decay
3. core
4. mantle
5. crust
a. ca. 40 km under continents
b. as little as 5 km thick under some parts of ocean
6. no life on Earth for ca. first billion years; life arose ca. 3.8 billion years ago
7. early atmosphere of Earth was a reducing one
a. no free O₂
b. CH₄, CO₂, NH₃, H₂, N₂, H₂O

D. Origin of Life on Earth

1. The following represents a superficial overview of science's best explanation for how life on Earth may have formed from non-life. There is still a great deal of work to be done in this area.
2. non-living materials (simple molecules) combined into more complex molecules that were eventually able to reproduce themselves.
a. amino acids, purines, and pyrimidines formed from simpler molecules (those available in the reducing atmosphere)
- Stanley Miller's experiments
b. monomers combined to form polymers
c. nucleic acid polymers can copy themselves (chemical "reproduction")\
3. main path of information in living organisms is DNA -> RNA -> protein
4. problem - proteins (enzymes) are used in all steps of this problem
a. DNA synthesis (replication)
b. protein synthesis
c. but proteins are constructed according to info in nucleic acids
5. so how did nucleic acids copy themselves without enzymes for copying themselves?
a. discovery of ribozymes (catalytic RNA)
b. hypothesis - RNA was the first information carrying molecule and some RNA had catalytic capability
c. experiments
- started with random sequence RNA, ended with highly catalytic RNA
- started with RNA and individual nucleotides; polynucleotides formed
6. As soon as molecular self-replication was possible, selection would begin to act.
a. Any changes ("mutations") in a molecule that favored more efficient replication would result in that type of molecule becoming more abundant
b. implications - from this point, the process is nonrandom
7. how did first cells form?
a. many different solutions that contain polymers will form coaceruates (round structures similar to cell membranes)
b. selection again - RNA contained in membranes probably left more copies of itself than membrane-free RNA
8. Membranes would have made homeostasis possible.
9. use of energy