[GE CLST 70B] - Midterm Exam Guide - Comprehensive Notes for the exam (17 pages long!)

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GE CLST 70B
MIDTERM EXAM
STUDY GUIDE
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GE70B Evolution of Cosmos and Life-Lecture 3: Geologic Time, Fossils, & The Earliest
Life
I. Fossils: Evidence of past life, including body, chemical, and trace fossils
A. Includes:
1. Whole body fossils
a) Mummification, frozen and bog specimens, amber
2. Preservations of the hard parts-petrification
3. Molds and casts
4. Trace fossils
a) Footprints, trackways
(1) Can show if animals traveled in packs or by themselves
5. Chemical traces
II. Taphonomy: The study of the processes by which animals become fossilized
A. Consumption and decomposition
B. Exposure and weathering
C. Transport and burial
D. Fossilization and exhumation
E. Lagerstatte: fossil localities with exceptional preservation
III. Geologic Time
A. Uniformitarianism
1. Concept of “deep time”-large amounts of time and recurring processes
can account for the observations we make today
2. Present is the key to the past
3. Opposed to catastrophism theory
B. Relative dating
1. Basically dating things by comparing them to other things
2. Unconformities: gap time in the sedimentary record, occurs when no
fossils or sediments are deposited or some erosion occurred
3. Index fossils
a) Easily distinguishable
b) Widespread
c) Short periods of geologic time
d) Abundant and easy to find
e) Use them to do “fossil correlation” and Biostratigraphy
f) Allowed for the creation of the “Geologic Time Scale”
C. Absolute Dating
1. Achieved through studying radioactivity
2. When combined with relative dating, they can be used to find the
sequence of past geological events
D. Geologic Time Scale (and dates to know)
1. Oldest minerals on earth-4.5 Ga
2. Oldest rocks on earth- 4 Ga
3. Oldest record of Life- 3.5 Ga
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4. Beginning of Phanerozoic Eon/Paleozoic Era-550 ma
a) Ended by P/T extinction
5. Beginning of Mesozoic Eara- 245 mya
a) LONG time of the dinosaurs
b) Ended by K/T extinction
6. Beginning of Cenozoic Era- 65 mya
IV. Brief History of Early Life
A. Origin of Life
1. Happened after late heavy bombardment concluded
B. Early Atmosphere
1. Methane, water, ammonia, nitrogen, carbon dioxide, not much oxygen
a) Could have come from interstellar space
2. Lots of energy
a) Lightening
b) Volcanoes and vents
c) UV light was strong because there was no ozone layer
3. Miller-Urey Experiment
a) Tried to recreate early Earth conditions in an lab to see if they
would start “life” which didn’t necessarily happen, but complex,
organic molecules and materials that lead to life did get created
C. The RNA world
1. One of the first self replicating molecules
a) Carries information and also acts as an enzyme for other
reactions
b) Probably became DNA
D. Earliest Life
1. Microscopic “smudges”
2. Autotrophs vs. Heterotrophs
a) Autotrophs make their own energy and molecules
b) Heterotrophs eat other things to get the organic material they
need
3. Prokaryotes vs. Eukaryotes
a) Prokaryotes (bacteria, archaea)
(1) No organelles
(2) Free floating DNA (no nucleus)
(3) Smaller
(4) No cytoskeleton
b) Eukaryotes (animals, plants, fungi)
(1) Nucleus with DNA inside
(2) Internal membranes
(3) Mitochondria w/ double membrane
(4) Larger
(5) Cytoskeleton
c) Eukaryotes were created through symbiosis of bacteria
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