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The Origin of Life
Notes:
Chapter 14
The Beginning:


Earth is about 4.6 billion years old
Life began on Earth about 3.5 billion years ago
in the ocean
Evidence of Life:
Fossils: remains of organisms, found
in sedimentary rock
 Relative Dating: lower rocks are older
than higher ones
 Radiometric Dating: using radioactive
isotopes in rocks because rate of
decay is related to half-life

Relative Dating:
Radiometric Dating:
How does life arise?

Spontaneous generation: life
from nonliving things
– Francesco Redi: disproved theory
by showing that flies must come
from other flies
How does life Arise?

Spontaneous generation:
– Louis Pasteur: concluded that microorganisms
must come from other microorganisms using Sshaped flasks that let in only air = no organisms

Biogenesis: life only from other living things
– Miller & Urey: showed that organic molecules
could have formed the beginning of life
The origin of cells:

Anaerobic prokaryotes: lived in an
atmosphere with no oxygen

The origin of cells:

Aerobic organisms: evolved once
photosynthesis released oxygen
The origin of cells:

Prokaryotes: cells without a nucleus or
organelles

Eukaryotes: cells with a nucleus and
organelles
– cells grew in complexity once conditions for life
improved
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