IB Biology
Option D
D1 Origin of Life on Earth
D.1.1 Describe four processes needed for the
spontaneous origin of life on Earth
1) The non-living synthesis of simple ______________________:
• Obviously if nothing was alive yet, then the source of these
molecules had to be _______________
• We can presume that the early Earth had all of the base
elements and compounds required
• They were somehow combined to make _______________
_____________________
• Maybe the organic compounds
were generated here, maybe they
were _______________________!
D.1.1 Describe four processes needed for the
spontaneous origin of life on Earth
2) The assembly of these molecules into _______________:
• In order to make the larger molecules necessary for life,
the simple organic compounds would have to _________
3) The origin of _____________________ molecules made
inheritance possible:
• DNA can’t self replicate, it needs protein enzymes
• However some ______ can self-replicate - it can catalyze
the formation of copies of itself.
• They are called ______________ and are the basis of the
RNA World Hypothesis
D.1.1 Describe four processes needed for the
spontaneous origin of life on Earth
4) The packaging of these molecules into _______________
with internal chemistry different from their surroundings:
• The formation of _________________an important step
• Closed membrane vesicles can form spontaneously
from ____________
• This allowed ________________ between the internal
and external environments
D.1.2 Outline the experiments of Miller and Urey
into the origin of organic compounds
Earth’s atmosphere was _____________ in the early
days. It did not contain __________ gas until after plants
started photosynthesizing
Can you
identify these
molecules?
D.1.2 Outline the experiments of Miller and Urey into
the origin of organic compounds
Earth’s atmosphere was ‘reducing’ in the early days.
It did not contain oxygen gas until after plants
started photosynthesizing
The atmosphere
contained:
The gases came
from abundant
volcanic activity
D.1.2 Outline the experiments of Miller and Urey into
the origin of organic compounds
These monomers mixed in the ________________, shallow oceans
with chemicals, where it is thought that they reacted to form
biological molecules
Miller and Urey tried to recreate these conditions in
the lab in 1953
They were trying to demonstrate ___________________, the
formation of more complex molecules from simpler stock in the
primordial soup
They combined the molecules from the previous page in a
closed glass vessel (simulated ___________), they heated the
water (simulated __________________) and sparked electricity
through the gases (simulated ____________)
D.1.2 Outline the experiments of Miller and Urey into
the origin of organic compounds
D.1.2 Outline the experiments of Miller and Urey into
the origin of organic compounds
D.1.2 Outline the experiments of Miller and Urey into
the origin of organic compounds
After a week they found:
Thirteen of the twenty naturally occurring ___________________
Around 15% of the carbon was now
in organic compounds
D.1.3
State that comets may have delivered
organic compounds to Earth
______________ is the hypothesis
that life on Earth originated from
material delivered by a _________,
either in the form of amino acids or
as hardy bacteria
Space is so
empty, yet full
of the
potential for
life
Existing bacteria and archaebacteria have been found
in odd and extreme environments on Earth:
In hot springs, kilometres deep in the crust and even
embedded in ice cores from deep inside Antarctica
It is feasible that they could survive on or in a comet
D.1.3
State that comets may have delivered
organic compounds to Earth
__________________ could
provide the energy for reactions
that lead to the formation of
complex organic molecules
Analysis of the spectra of light
coming from the comets reveals
the presence of hydrocarbons,
_______________ and peptides
The bombardment of
Earth by comets ___
________ years ago
could have ‘kick
started’ chemical
evolution
D.1.3
State that comets may have delivered
organic compounds to Earth
The hypothesis that life came an extraterrestrial source:
As previously mentioned, ___________________ are out there
Mars is smaller than Earth and therefore ______
______ more quickly, life could have begun there
while Earth was still scorching
Meteorites and comets impacting on mars could have
thrown up debris with early life attached, this could then
have crashed on Earth. Meteorites of Mars origin have
been found in Antarctica
D.1.3
State that comets may have delivered
organic compounds to Earth
The hypothesis that life came an extraterrestrial source:
There is no evidence that life has been transferred in this way.
Every now and then there is a news story about “Fossils found
in Mars meteorite” but so far this has not been confirmed
The extraterrestrial hypothesis still doesn’t address how life
formed, just how it could _____________________________
D. 1.4 Discuss possible locations where conditions
would have allowed the synthesis of organic
compounds
• Locations needed to be a
____________ (electron adding)
environment to encourage
compound formation
• communities around
– deep-sea _________________
– ______________
– ________________ locations
(carried to earth on a comet).
D.1.5 Outline Two properties of RNA that would have
allowed it to play a role in the origin of life
RNAs can store, transmit and replicate genetic Information
• RNA is composed of a ________________. The
bases are exposed and ready to combine with a
complement, making replication simpler
• RNA was probably the first hereditary molecule
having the ability to __________________
• RNA shows enzymatic (__________) properties
– called _______________
– Ribozyme: an RNA molecule that
catalyzes a chemical reaction
D.1.5 Outline Two properties of RNA that would have
allowed it to play a role in the origin of life
• Once RNA became enclosed in __________, these
protobionts would have a form of ________.
• These protobionts may be selected
for ___________.
• RNA may have directed the sequencing of
______________to form primitive enzymes.
D.1.6 State that living cells may have been preceded
by protobionts, with an internal chemical
environment different from their surroundings
• Origin of cell formation
 Began as _________________
 Separate inside from outside
 Divide often (______________)
 Grow larger in size
Bubbles…
 Maintain a level of ______________ internally
Tiny bubbles…
 Produce __________________across surfaces
 Absorbs materials from the surface (________
______________)
 ___________ actvity
D.1.6 State that living cells may have been preceded
by protobionts, with an internal chemical
environment different from their surroundings
Protobionts = Aggregation of abiotically produced
molecules in ___________
- Maintain an _____________________ different from
their surroundings.
- Exhibit some properties associated with life:
___________ and ____________
- May have arisen from ____________, ___________,
or _____________
D.1.6 State that living cells may have been preceded
by protobionts, with an internal chemical
environment different from their surroundings
• Coacervate = droplets 1. Colloidal suspension of
_______________
of _________________
2. A water film acts as a barrier
like a __________________
3. _________ in size
4. When large enough, it
_______________ into small
globules with the same
traits as that of the “parent”
D.1.6 State that living cells may have been preceded
by protobionts, with an internal chemical
environment different from their surroundings
• Microsphere = polypeptides with a semipermeable
____________________





formed by adding _________ to polypeptides
show an ________________________ - may absorb materials
from the surrounding environment
membranes are made of phospholipid bilayers with __________
may give clues to the evolution of the
cell membrane
undergo shrinking and swelling due to
_____________
D.1.6 State that living cells may have been preceded
by protobionts, with an internal chemical
environment different from their surroundings
• Liposome = form spontaneously when the organic
molecules includes ___________


Form ________________membrane
Grow by __________ other liposomes and may split to form two
D.1.6 State that living cells may have been preceded
by protobionts, with an internal chemical
environment different from their surroundings
How Polymerization could Occur?
• _____ was thought to be a possible site for
polymerization (rather than primordial soup in the sea)
• ________ well to organic molecules
• Contains Zinc, iron, nickel, etc serving as a __________
• Has been shown to occur experimentally:
dry clay...heat it...200 amino acids can spontaneously join &
form polypeptides!! ...can possibly form ______________
D.1.7 Outline the contribution of prokaryotes to the
creation of an oxygen-rich atmosphere
• Prokaryotes dominated life
on Earth from ________________
3.5 billion year old
fossil of bacteria
modern bacteria
chains of one-celled
cyanobacteria
D.1.7 Outline the contribution of prokaryotes to the
Lynn Margulis
creation of an oxygen-rich atmosphere
 The first cells were ___________
 __________________ offer more fossil evidence
– rocklike columns composed of many minute layers of
prokaryotic cells (usually ________________)
 Living stromatolite reefs are still found in ___________ and
in warm, shallow pools of fresh and salt water
D.1.7 Outline the contribution of prokaryotes to the
creation of an oxygen-rich atmosphere
Fossilized Stromatolites
– 3.5 billion years old
Modern day
stromatolites
D.1.7 Outline the contribution of prokaryotes to the
creation of an oxygen-rich atmosphere
• Oxygen begins to accumulate ________
– reducing  ___________ atmosphere
• evidence in banded iron in rocks = _______
• makes ____________________ possible
– photosynthetic bacteria (______________)
D.1.7 Outline the contribution of prokaryotes to the
creation of an oxygen-rich atmosphere
•
•
•
first photosynthetic organism were autotrophs which split _____
as a hydrogen donor (purple and green sulfur bacteria)
the first photosynthetic organisms to use _____ as a hydrogen
donor were the cyanobacteria (released _____ as by-product)
source of the first free oxygen in aquatic environment and
atmosphere – O2 existed in significant quantities by _________
________
D.1.7 Outline the contribution of prokaryotes to the
creation of an oxygen-rich atmosphere
The increase in Oxygen led to:
• The breakdown of the chemicals in the ‘chemical
soup’ to ______________and oxidized sediments
• The formation of the ______________, which
blocked out UV and stopped the production of more
of the ‘soupy’ molecules
• The oxygen concentration rose to 0.45% of the
atmosphere - not much compared to today’s 21%,
but it led to the rise of the _____________
D.1.8 Discuss the endosymbiotic theory for the origin
of eukaryotes
Endosymbiosis is the theory that ____________ and
_____________ were once free-living prokaryotes that
were engulfed by larger prokaryotes and survived to
evolve into the modern organelles
D.1.8 Discuss the endosymbiotic theory for the origin
of eukaryotes
First Eukaryotes ~_______
• Development of ________________
– create internal micro-environments
– advantage: ______________ = increase efficiency
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
D.1.8 Discuss the endosymbiotic theory for the origin
of eukaryotes
Endosymbiosis
• Evolution of eukaryotes
– origin of mitochondria
– engulfed _________________, but
did not digest them
– ___________________ relationship
internal membrane
system
aerobic bacterium
mitochondrion
Endosymbiosis
Ancestral
eukaryotic cell
Eukaryotic cell
with mitochondrion
D.1.8 Discuss the endosymbiotic theory for the origin
of eukaryotes
Eukaryotic
cell with
mitochondrion
Endosymbiosis
• Evolution of eukaryotes
– origin of chloroplasts
– engulfed _____________________,
but did not digest them
– ____________________ relationship
photosynthetic
bacterium
chloroplast
Endosymbiosis
Eukaryotic cell with
chloroplast & mitochondrion
mitochondrion
D.1.8 Discuss the endosymbiotic theory for the origin
of eukaryotes
• Evidence
Theory of Endosymbiosis
– structural
• mitochondria & chloroplasts
resemble _____________________
– genetic
• mitochondria & chloroplasts
have their own _______________, like bacteria
– functional
• mitochondria & chloroplasts
move _________ within the cell
• mitochondria & chloroplasts
reproduce ________________ from the cell