Transcript The History of Life

The History of Life
14.2 The origin of Life
The Origin of Life: Early Ideas
People saw maggots
appear on rotting meat
 People saw mice appear
in food storage
 Thought that living
things sprouted from the
non-living
The Origin of Life: Early Ideas
 Spontaneous
generation is the
idea that non-living material can
produce life
The Origin of Life: Early Ideas
 In
1668 Francesco Redi showed that
living things did not come from nonliving
The Origin of Life: Early Ideas
 People
still believed that life must
arise from somewhere
– Maybe from some vital force in the air
The Origin of Life: Early Ideas
 In
mid-1800s Louis Pasteur showed
that living things
would not arise
from air
The Origin of Life
 Biogenesis
– the idea that living
things come only from other living
things
 Biogenesis became cornerstone of
biology
 But how did the first life on Earth
begin?
The Origin of Life: Modern ideas
 For
life on Earth to begin
– Molecules that contain carbon form
 Organic
molecules
– Then are organized into complex
molecules
 Proteins,
carbohydrates, nucleic acids
The Origin of Life: Modern ideas

1930s Russian
Alexander Oparin said
– Heat from lightning on
the oceans triggered
formation of organic
molecules

1953 Americans
Miller and Urey
– Simulated the conditions
of early Earth
– Supported Oparin’s
hypothesis
The Origin of Life: Modern ideas
 1950s
experiments showed that
organic molecules in heated water
form complex molecules like
proteins, ATP
 American Sydney Fox showed that
amino acid chains can
form protocells
The Origin of Life: Modern ideas
 Protocells
are large structures with a
membrane that carry out life
activities like growth and division
 Protocells evolved to prokaryotes
The Origin of Life: Modern ideas
 The
first prokaryotes were
– Anaerobic – without oxygen
– Heterotrophs – don’t make own food
The Origin of Life: Modern ideas
 Next:
Archaebacteria
– Prokaryotes that live in harsh environs
– Autotrophs – make own food
– Chemosynthesis – get energy from
inorganic compounds in the environment
The Origin of Life: Modern ideas
 Then:
Prokaryotes that get food from
photosynthesis
 Start to make oxygen
The Origin of Life: Modern ideas
 Eukaryotes
team up
evolve when prokaryotes
– Proposed by American Lynn Margulis 1960