Download First Life Forms Roles of RNA

History of Life
PP 280-290
Biogenesis
Biogenesis: life comes from other living
organisms
Spontaneous generation: early and
disproved theory that life comes from nonliving organisms
Evidence Against Spontaneous
Generation
Redi’s experiment: indicated that maggots
didn’t come from rotting meat because
flies couldn’t land
Spallanzani’s experiment:
disproved that organisms came
from “vital force” by preventing
air contact
Pasteur’s experiment: showed that microorganisms in the air contaminated the flasks
disproving “vital force”
First Life Forms
First organic compounds
Oparin: hypothesized that
primitive Earth’s atmosphere
was NH3, H2, H2O, and CH4
Miller-Urey: produced
organic compounds based on
the hypothesized
composition
First Cell
Protocell:
consisted of a
simple lipid
membrane and
genetic material
Fox: formed membrane
bound structures in the lab
(droplets of amino acids
and sugars)
First Genetic Material
Role of RNA
• RNA is less complex than DNA
• Ultimately DNA is a more stable molecule
• RNA is able to catalyze reactions like
enzymes
• It is the main component that links DNA
to protein synthesis
First Life Forms
Anaerobic before Aerobic
• Earth’s early atmosphere lacked oxygen
• Anaerobic respiration had to be first
First Life Forms
continued
Heterotrophic before autotrophic
The carbon dioxide generated from
heterotrophs could be used by autotrophs
First Life Forms
cont
Chemosynthetic before Photosynthetic
• The sun was blocked by atmospheric
gases so chemosynthesis came first
• Eventually photosynthetic organisms
helped to generate oxygen
First Life Forms
cont
Prokaryotes before eukaryotes
• Eukaryotes have organelles with specialized
functions
• Prokaryotes are smaller than eukaryotes
The First Eukaryotes
• Mitochondria and chloroplasts are thought to
be prokaryotic cells that were engulfed by a
bigger cell
• This theory is called endosymbiosis