Transcript Early Earth and The Origin of Life

Early Earth and
The Origin of Life
Chapter 20
The Origin and Evolution
of Life
Chapter 20
The Big Bang
• 12-15 billion years ago all matter was
compressed into a space the size of our
sun
• Sudden instantaneous distribution of
matter and energy throughout the known
universe
Earth Forms
• 4,600 mya: Origin of Earth
• 4,600 - 3,800 mya
– Formation of Earth’s crust, atmosphere
– Chemical and molecular evolution
– First cells (anaerobic bacteria)
Earth Forms
• About 4.6 and 4.5 billion years ago
• Minerals and ice orbiting the sun
started clumping together
• Heavy metals moved to Earth’s interior,
lighter ones floated to surface
• Produced outer crust and inner mantle
Earth Is “Just Right” for Life
• Smaller in diameter, gravity would not be
great enough to hold onto atmosphere
• Closer to sun, water would have
evaporated
• Farther from sun, water would have been
locked up as ice
First Atmosphere
• Hydrogen gas
• Nitrogen
• Carbon monoxide
• Carbon dioxide
• No gaseous oxygen
Origin of Organic Compounds
• Amino acids, other organic compounds can form
spontaneously under conditions like those on
early Earth
• Clay may have served as template for complex
compounds
• Compounds may have formed near
hydrothermal vents
• Oparin hypothesized that energy from lightning
could have caused organic molecules to form
from inorganic compounds in Earth’s primitive
atmosphere.
Miller-Urey Experiment
• In 1953, Miller and Urey did an experiment
that simulated lab conditions that were
similar to those of the early Earth
• After one week, they found a variety of
organic compounds (including amino
acids) that had been produced from
inorganic material
Miller-Urey Experiment
Chemical
Evolution
• Spontaneous
formation of
porphyrin rings from
formaldehyde
• Components of
chlorophylls and
cytochromes
chlorophyll a
formaldehyde
porphyrin ring system
Figure 20.4
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RNA World
• DNA is genetic material now
• DNA-to-RNA-to-protein system is complicated
• RNA may have been first genetic material
• RNA can assemble spontaneously and can carry
out enzyme-like catalytic functions. (These
enzyme-like, self-replicating pieces of RNA are
known as ribozymes.)
• How switch from RNA to DNA might have occurred
is not known. Ribozymes might have somehow
served as a template for DNA production.
Proto-Cells
• Microscopic spheres of proteins or lipids
can self assemble
• Tiny sacs like cell membranes can form
under laboratory conditions that simulate
conditions in evaporating tidepools
Protobionts
• Collections of abiotically produced
molecules surrounded by a membrane
• Exhibit simple reproduction and
metabolism.
• Small membrane bound droplets called
liposomes can form when lipids are added
to water.
Possible
Sequence
membrane-bound proto-cells
living
cells
self-replicating system enclosed in a
selectively permeable, protective lipid sphere
DNA
RNA
formation of
protein-RNA systems,
evolution of DNA
enzymes and
other proteins
formation of
lipid spheres
spontaneous formation of lipids,
carbohydrates, amino acids, proteins,
nucleotides under abiotic conditions
Figure 20.5
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Proterozoic Eon
• Origin of photosynthetic Eubacteria
– Noncyclic pathway first
– Cyclic pathway next
• Oxygen accumulates in atmosphere
• Origin of aerobic respiration
The First Cells
• Originated in Archeon Eon
• Were prokaryotic heterotrophs
• Secured energy through anaerobic
pathways
– No oxygen present
– Relied on glycolysis and fermentation
History of Life
ARCHAEBACTERIAL
LINEAGE
ANCESTORS OF
EUKARYOTES
ORIGIN OF
PROKARYOTES
Noncyclic pathway
Cyclic pathway of of photosynthesis
photosynthesis
Aerobic respiration
Figure 20.6
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3.8 bya
3.2 bya
2.5 bya
History of Life
ARCHAEBACTERIA
Extreme halophiles
Methanogens
Extreme thermophiles
ORIGINS OF EUKARYOTES
ORIGINS OF
MITOCHONDRIA
ORIGINS OF ANIMALS EUKARYOTES
Animals
Heterotrophic protistans
ORIGINS OF FUNGI
Fungi
Photosynthetic protistans
ORIGINS OF PLANTS Plants
ORIGINS OF
CHLOROPLASTS
EUBACTERIA
Photosynthetic oxygen producers
Other photosynthetic bacteria
Chemotrophs, heterotrophs
1.2 bya
900 mya
435 mya
present
Figure 20.6
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Advantages of Organelles
• Nuclear envelope may have helped to protect
genes from competition with foreign DNA
• ER channels may have protected vital proteins
DNA
Figure 20.10
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infolding
of plasma
membrane
Theory of Endosymbiosis
• Lynn Margulis
• Mitochondria and chloroplasts are the
descendents of free-living prokaryotic
organisms
• Prokaryotes were engulfed by early
eukaryotes and became permanent
internal symbionts
Timeline of Life on Earth
Kingdoms of Life
• Arranging the diversity of life into
kingdoms is a work in progress
• There are multiple ways to categorize the
forms of life
• Some diagrams to be familiar with…
Kingdoms of Life
Most do not
use this 5
kingdom
system today!
Kingdom
Monera has
been divided
into two
kingdoms.
Kingdoms of Life
Classification Levels
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Domain
Kingdom
Phylum/Division (for plants & fungi)
Class
Order
Family
Genus
Species
Classification Scheme
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Based on work of Carolus Linnaeus
Father of taxonomy
Father of binomial nomenclature
Genus species
Genus is a noun that describes the organism.
Species name is an adjective describing it.
Genus (capitalized & underlined)
species (never capitalized & underlined)
Classification of Living Things
Domain
Kingdom
Cell Type
Bacteria
Archaea
Eubacteria
Archaebacteria
Prokaryote
Prokaryote
(no membrane
bound nucleus;
few
membranous
organelles)
Cells walls
Cell
Structures with
peptidoglycan
Protista
Eukaryote
(Membranebound nucleus
with many
organelles)
Fungi
Eukaryote
Eukarya
Plantae
Eukaryote
Cell walls
without
peptidoglycan
Cells calls of
Cell walls with
cellulose in
chitin
some; some have
chloroplasts
Cell walls of
cellulose;
chloroplasts
Animalia
Eukaryote
No cell walls;
No chloroplasts
# of cells
Unicellular
Unicellular
Most
Unicellular;
some simple
multicellular
Most multicellular; Multicellular
some unicellular
(yeasts)
Multicellular
Mode of
Nutrition
Autotroph or
Heterotroph
Autotroph or
Heterotroph
Autotroph or
Heterotroph
Heterotroph
Autotroph
Heterotroph
Examples
Streptococcus; Methanogens,
Escherichia
Halophiles
coli
Thermophiles
Amoeba;
Paramecium;
Euglena
Algae; Kelp
Mushrooms;
molds; mildew;
yeast
Mosses; ferns,
gymnosperms(co
nifers);
Angiosperms
(flowering
plants)
Sponges,
worms, insects,
fishes,
mammals, etc.