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8-2 NOTES: HISTORY OF LIFECHAPTER 14
AGE OF EARTHThe earth is about 4.5 billion years old
How did we measure that?
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AGE OF EARTHThe earth is about 4.5 billion years old
How did we measure that?
• Radiometric Dating = calculating the age of an object by measuring proportions of radioactive isotopes
RADIOMETRIC DATINGRadioactive Isotope = an unstable form of an element, decays into stable element, gives off energy (radiation)
• Ex. Carbon-14 decays into Nitrogen • Ex. Potassium-40 decays into Argon-40
RADIOMETRIC DATINGHalf-life = the time it takes for half of a radioactive isotope to decay
• Ex. K-40 half life is 1.3 billion years
PRACTICE
The half life of carbon-14 is 5,730 years. If only 25% of the original amount of carbon-14 is left in an object, how hold it the object?
PRACTICE
The half life of carbon-14 is 5,730 years. If only 25% of the original amount of carbon-14 is left in an object, how hold it the object?
1.Determine how many half lives have elapsed.
• 25% or ¼ = 2 half lives
PRACTICE
The half life of carbon-14 is 5,730 years. If only 25% of the original amount of carbon-14 is left in an object, how hold it the object?
1.Determine how many half lives have elapsed.
• 25% or ¼ = 2 half lives
2.Multiply this by the known half life.
• Carbon half life = 5,730 years• 2(5,730 yrs) = 11,460 years
FIRST ORGANIC COMPOUNDS
Spontaneous Origin: organic compounds developing from non-living chemical reactions
SPONTANEOUS ORIGINOparin: (1920) Hypothesized that primitive Earth’s atmosphere was:
• NH3 (ammonia)
• H2
• H2O• CH4 (methane)
No Oxygen!
SPONTANEOUS ORIGIN
Miller-Urey: (1953) Produced organic compounds (amino acids) based on the hypothesized composition of early earth’s atmosphere
FIRST LIFE FORMS - THE FIRST CELLS
Prokaryotes before eukaryotes
FIRST LIFE FORMS - THE FIRST CELLS
Prokaryotes before eukaryotes
3 major trends all interrelated:
•Anaerobic Aerobic
Inferences based on early earth environment having:1. No Oxygen Gas
(anaerobic)
FIRST LIFE FORMS - THE FIRST CELLS
Prokaryotes before eukaryotes
3 major trends all interrelated:
•Anaerobic Aerobic
•Heterotrophic Autotrophic•Chemosynthetic Photosynthetic
Inferences based on early earth environment having:1. No Oxygen Gas
(anaerobic)2. Many organic
molecules for food (hetero)
3. Extreme harsh conditions (chemosynthetic)
THE FIRST EUKARYOTES
ENDOSYMBIOSIS THEORY
• Mitochondria (aerobic prok) and chloroplasts (chemosynthetic prok) are thought to be prokaryotic cells that were engulfed by a bigger prokaryote.
• Created mutual beneficial relationship• Bigger prokaryote provided a beneficial environment• Smaller prokaryote provided a source of energy
THE FIRST EUKARYOTES
ENDOSYMBIOSIS THEORY
• Mitochondria (aerobic prok) and chloroplasts (chemosynthetic prok) are thought to be prokaryotic cells that were engulfed by a bigger prokaryote.
Supporting Evidence:
• Both organelles contain their own DNA• DNA is circular (like other prokaryotes)• Can replicate on their own.
PUT THESE IN THE ORDER IN WHICH THEY ARE THOUGHT TO HAVE ORIGINATED ON EARTH
1. Anaerobic heterotrophic prokaryotes
2. Aerobic eukaryotes
3. Chemosynthetic prokaryotes
4. Photosynthetic prokaryotes
Answer: 1, 3, 4, 2
SEQUENCE OF FIRST CELLSAnaerobicHeterotrophicProkaryotes
ChemosyntheticProkaryotes
PhotosyntheticProkaryotes
PhotosyntheticEukaryotes
AerobicEukaryotes
Endosymbiosis Occurs Here!
