Transcript 3.1 Origin of Life - Welcome to the Greater Albany Public

Origin of Life
(Ch. 26)
2006-2007
the right
combination of
physical events &
chemical
processes…”
500
Millions of years ago
1000
1500
2000
2500
3000
3500
Cenozoic
Mesozoic
Paleozoic
ARCHEAN
PROTEROZOIC
PRECAMBRIAN
0
Colonization of land
by animals
Appearance of animals
and land plants
First multicellular
organisms
Bacteria Archae- Protista Plantae Fungi
bacteria
Animalia
Oldest definite fossils
of eukaryotes
Appearance of oxygen
in atmosphere
Oldest definite fossils
of prokaryotes
4000
Molten-hot surface of
earth becomes cooler
4500
Formation of earth
• The evolutionary tree of
life can be documented
with evidence.
• The Origin of Life on
Earth is another story…
What is Life?
• First we have to define LIFE…
– organized as cells
– respond to stimuli
– regulate internal processes
• homeostasis
– use energy to grow
• metabolism
– develop
• change & mature
within lifetime
– reproduce
• heredity
– DNA / RNA
• adaptation & evolution
Life comes from Non-Life
• Where is the line between living
and non-living?
• “A vehicle (organism) built by
No worries—
design information (DNA) for the Alive or Not,
I exist!!!
purpose of replicating that
information”
• Good– but too inclusive???
(computer viruses, etc.)
• Terrestrial life is cellular (sorry
viruses).
The Origin of Life is Hypothesis
• Special Creation
– Life was created by a supernatural or
divine force.
– not testable
• Extraterrestrial Origin (Panspermia)
– The original source of organic
(carbon) materials was comets &
meteorites striking early Earth.
– testable
• Spontaneous Abiotic Origin
– Life evolved spontaneously from
inorganic molecules.
– testable
Conditions on early Earth
• Reducing atmosphere
– water vapor (H2O), CO2, N2, NOx, H2, NH3,
CH4, H2S
– lots of available H & its electron
– no free oxygen
low O2 =
• Energy source
– lightning, UV radiation,
volcanic
What’s missing
from that
atmosphere?
organic molecules
do not breakdown
as quickly
5 Steps to go from Non-Life to
Life
1. Formation (or presence) of Biological
Molecules
2. Isolation of Biological Molecules from
Surroundings (aka “Cells”)
3. Development of Metabolism.
4. Development of Information Molecules.
5. Reproduction.
Origin of Organic
Molecules
Electrodes discharge
sparks
(lightning simulation)
• Abiotic synthesis
– 1920
Oparin & Haldane
propose reducing
atmosphere
hypothesis
– 1953
Miller & Urey
test hypothesis
Water vapor
NH3
Mixture of gases
("primitive
atmosphere")
H2
Condenser
Water
• formed organic
compounds
–amino acids
–adenine
CH4
Heated water
("ocean")
Condensed
liquid with
complex,
organic
molecules
Stanley Miller
University of Chicago
produced
-amino acids
-hydrocarbons
-nitrogen bases
-other organics
It’s ALIVE!
Origin of Cells (Protobionts)
• Bubbles  separate inside from outside
•
 metabolism & reproduction
Glucose-phosphate
20
m
Glucosephosphate
Phosphorylase
Starch
Phosphate
Bubbles…
Tiny bubbles…
Amylase
Maltose
Maltose
(a) Simple reproduction.
This liposome is “giving
birth” to smaller
liposomes (LM).
(b) Simple metabolism. If enzymes—in
this case, phosphorylase and
amylase—are included in the
solution from which the droplets selfassemble, some liposomes can carry
out simple metabolic
reactions and export the products.
Origin of Genetics
Dawn of
natural selection
• RNA is likely first genetic material
– multi-functional
– codes information
• self-replicating molecule
• makes inheritance possible
• natural selection & evolution
– enzyme functions
• ribozymes
• replication
– regulatory molecule
– transport molecule
• tRNA & mRNA
A ribozyme capable of replicating RNA
Ribozyme
(RNA
molecule)
3

Templat
e
Nucleotide
s
Complementary RNA
copy
5

5

Key Events in Origin of Life
• Key events in
evolutionary
history of life on
Earth
– life originated
3.5–4.0 bya
– “Heterotroph
Hypothesis”:
cells eating other
cells for ~700
million years.
Prokaryotes
• Prokaryotes dominated life
on Earth from 3.5–2.0 bya
3.5 billion year old
fossil of bacteria
modern bacteria
chains of one-celled
cyanobacteria
Stromatolites
• Fossilized mats of
prokaryotes resemble
modern microbial
colonies
Lynn Margulis
Oxygen atmosphere
• Oxygen begins to accumulate 2.7 bya
– reducing  oxidizing atmosphere
• evidence in banded iron in rocks = rusting
• makes aerobic respiration possible
– photosynthetic bacteria (blue-green algae)
First Eukaryotes
~2 bya
• Development of internal membranes
– create internal micro-environments
– advantage: specialization = increase efficiency
• natural selection!
infolding of the
plasma membrane
plasma
membrane
endoplasmic
reticulum (ER)
nuclear envelope
nucleus
DNA
cell wall
Prokaryotic
cell
Prokaryotic
ancestor of
eukaryotic
cells
plasma
membrane
Eukaryotic
cell
Endosymbiosis
• Evolution of eukaryotes
– origin of mitochondria
– engulfed aerobic bacteria, but
did not digest them
– mutually beneficial relationship
• natural selection!
internal membrane
system
aerobic bacterium
mitochondrion
Endosymbiosis
Ancestral
eukaryotic cell
Eukaryotic cell
with mitochondrion
Endosymbiosis
• Evolution of eukaryotes
Eukaryotic
cell with
mitochondrion
– origin of chloroplasts
– engulfed photosynthetic bacteria,
but did not digest them
– mutually beneficial relationship
• natural selection!
photosynthetic
bacterium
chloroplast
Endosymbiosis
Eukaryotic cell with
chloroplast & mitochondrion
mitochondrion
Theory of Endosymbiosis
• Evidence
– structural
• mitochondria & chloroplasts
resemble bacterial structure
– genetic
Lynn Margulis
• mitochondria & chloroplasts
have their own circular DNA, like bacteria
– functional
• mitochondria & chloroplasts
move freely within the cell
• mitochondria & chloroplasts
reproduce independently
from the cell
Cambrian explosion
• Diversification of Animals
– within 10–20 million years most of the major phyla of
animals appear in fossil record
543 mya
Diversity of life & periods of mass extinction
600
100
Millions of years ago
400
300
200
500
Number of
taxonomic
Permian mass families
extinction
)
Extinction rate
2,500
2,000
60
1,500
40
Cretaceous
mass extinction
1,000
)
20 Cambrian
500
Paleozoic
Mesozoic
Cenozoic
Neogene
Paleogene
Cretaceous
Jurassic
Triassic
0
Permian
Devonian
Silurian
Ordovician
Cambrian
0
Carboniferous
explosion
Proterozoic eon
Extinction rate (
0
Number of families (
80
100
Cretaceous extinction
• The Chicxulub impact crater in the
Caribbean Sea near the Yucatan
Peninsula of Mexico indicates an asteroid
or comet struck the earth and changed
conditions 65 million years ago
Early mammal evolution
• 125 mya mammals
began to radiate
out & fill niches
Classifying Life
• Molecular data
challenges 5 Kingdoms
• Monera was too diverse
– 2 distinct lineages of prokaryotes
• Protists are still too diverse
– not yet sorted out
3 Domain system
• Domains = “Super” Kingdoms
– Bacteria
– Archaea
• extremophiles = live in extreme environments
– methanogens
– halogens
– thermophiles
– Eukarya
• eukaryotes
– protists
– fungi
– plants
– animals
Classification
Eukaryote
• Old 5 Kingdom system
• New 3 Domain system
Prokaryote
– reflects a greater
understanding of
evolution & molecular
evidence
• Bacteria
• Archaebacteria
• Eukaryotes
– Protists
– Plants
– Fungi
– Animals
Archaebacteria
&
Bacteria
Kingdom
Bacteria
Kingdom
Archaebacteria
Kingdom
Protist
Kingdom
Fungi
Kingdom
Plant
Kingdom
Animal
Any Questions??
Is there life elsewhere?
Does it look like life on Earth?
2006-2007
Have Humans Created Life?
Certainly not cellular life.
“Synthia” –
Created in 2010 by the Venter
Institute
Very simple bacterium with a
completely synthesized
chromosome
Some computer programs sure
behave a lot like life does...
Review Questions
2006-2007
• 1. What is (are) the drawback(s) associated with the
hypothesized abiogenetic formation of organic
monomers in early Earth's atmosphere? *
1) the relatively short time between
intense meteor bombardment and
appearance of the first life forms
2) the lack of experimental evidence
that organic monomers can form
abiogenetically
3) uncertainty about which gases
comprised early Earth's atmosphere
A.
B.
•
•
•
1 only
2 only
3 only
1 and 3
2 and 3
2. In the Miller- Urey experiment, application of electric
sparks to simple gasses resulted in the formation of
•
•
•
•
•
Steroids
Oxygen
Cellulose
Simple amino acids
DNA
The following questions refer to the following choices:
1.
2.
3.
4.
aerobic autotrophs
aerobic heterotrophs
anaerobic heterotrophs
anaerobic autotrophs
•What is the most likely order in which the choices above
evolved on Earth?
•Give two pieces of evidence to support your order for #3.