TOPIC 6
Origins of Life
DAY 2 – INTRO TO
MACROMOLECULES
OBJECTIVES
• Describe the basic molecular structure of
carbohydrates, lipids, proteins, and nucleic
acids.
• Describe the primary function of
carbohydrates, lipids, proteins, and nucleic
acids.
Macromolecule Where it is found
What it does
Protein
Meat, Fish, Cheese
Enzymes, structural,
transportation, hormones
among many other
functions in living
organism.
Carbohydrate
Sugar, Breads, Fruits,
Pasta, Rice
Short term energy
Lipid
Fats
Nucleic Acid
RNA and DNA
Long term energy
storage; an important
component of the cell
membrane.
Carries genetic
information
ESSENTIAL QUESTION
• You are composed of the same material
as all other living things on the planet
……How is this possible?
MACROMOLECULES ARE POLYMERS MADE UP OF
MANY MONOMERS
 Monomer - small molecular subunit which joins with similar
units to form a polymer.
 Polymer - consists of up to millions of repeated, covalently
linked monomers.
PROTEINS
 Are macromolecules that contain nitrogen as well as carbon,
hydrogen, and oxygen.
 Made up of a repeating chain of amino acids.
PROTEINS
 Are used to build muscle and can be found in beef, chicken, eggs, tofu, beans, and fish.
 Denature under exposure to heat – that’s what causes the egg to turn white!
HOW DID THE FIRST ORGANIC COMPOUNDS
FORM?

Experiment conducted in 1953 by
Staley L. Miller and Harold C. Urey

Their apparatus, illustrated in
the figure included a:
Gas chamber containing gases
present in Earth early atmosphere
 Electrodes supply electricity to
provide energy to drive chemical reactions
 Water chamber substituted for the oceans and lakes.
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The Miller-Urey experiment produced a variety of organic
compounds, including amino acids.
THEORIES OF THE
ORIGIN OF LIFE
WHAT ARE WE LEARNING TODAY?
Benchmarks
Learning Objectives
 SC.912.L.15.8 – Describe
 I will describe scientific
the scientific explanations
explanations of the origin of
of the origin of life on
life on Earth.
Earth.
 I will identify situations or
conditions contributing to
the origin of life on Earth.
WHAT IS THE ESSENTIAL QUESTION?
Scientists explain that that life arose from
nonlife billions of years ago through the
theory of abiogenesis. Could life arise from
nonlife today? Explain.
WHAT CONDITIONS MAKE EARTH
UNIQUE?


Only planet known to sustain life.
Several conditions make
Earth able to sustain life as
we know it.
 presence of liquid water
 moderate temperature
range
 free oxygen in the
atmosphere
 adequate sunlight
 no toxic substances in the atmosphere
 absence of lethal radiation
WHAT WAS EARTH LIKE?


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Earth’s early atmosphere probably contained hydrogen cyanide,
carbon dioxide, carbon monoxide, nitrogen,
hydrogen sulfide, and water.
Volcanic activity probably formed it.
 Released great amounts of water vapor
that later condensed to form oceans.
 Released CO 2 that warms the
atmosphere by absorbing outgoing heat.
How did that affect the temperature?
This early atmosphere lacked
oxygen, so it could not support life as
we know it today.
 WHERE DID LIFE BEGIN?
 HOW DID LIFE BEGIN?
 WHAT DID IT LOOK LIKE? SO MANY QUESTIONS!!!
WHERE DID LIFE BEGIN?
Fossil Evidence
 Fossil evidence indicates
that life on Earth
appeared about 3.5
billion years ago in the
oceans
 Provided protection
from UV radiation
 Allowed
multidirectional
movement
 Served as a medium
for essential chemical
reactions.
 Anaerobic prokaryotes
Primordial Soup Theory
 Proposed by Alexander Oparin and John
Haldane.
 Early atmosphere contain
NH3, CO2, H2O, H2, and CH4
 At high temperatures, these gases may
have formed single organic compounds.
 When Earth cooled and water vapor
condensed, these simple organic
compounds would have collected in lakes
and oceans.
 Overtime. these compounds could have
entered complex chemical reactions,
fueled by energy from ultraviolet radiation,
volcanic eruptions, and lighting.
ABIOGENESIS VS. BIOGENESIS
 Abiogenesis or spontaneous
generation states that life can arise
from nonliving things
 Oparin reasoned that O2 prevents
the synthesis of certain organic
compounds that are necessary
building blocks for the evolution of
life
 Oparin proposed that the
"spontaneous generation of life" did
in fact occur once, but was now
impossible because the conditions
found on the early Earth had
changed
 Oparin argued that a "primeval
soup" of organic molecules could be
created in an oxygen-less
atmosphere.
 Biogenesis states that every living
thing came from a pre-existing living
thing.
 In 1668 Francesco Redi, proved
that no maggots appeared in
meat when flies were prevented
from laying eggs.
 In 1768, Lazzaro Spallanzani
demonstrated that microbes
were present in the air, and
could be killed by boiling.
 In 1861, Louis Pasteur
performed a series of
experiments which demonstrated
that organisms such as bacteria
and fungi do not spontaneously
appear in sterile, nutrient-rich
media.
HOW DID LIFE BEGIN?
Hydrothermal Vents
Electric Spark
 These vents release
important hydrogen-rich
molecules
 Mineral catalysts could have
made critical reactions occurs
faster
 Can generate amino acids
and sugars from an
atmosphere loaded with
water, methane, ammonia
and hydrogen
 Demonstrated in the famous
Miller-Urey experiment
reported in 1953
 New evidence suggest
that it may have
occurred in volcanic
clouds
HOW DID LIFE BEGIN?
Panspermia
Community Clay
 Life could have come from
outer space in a comet or
meteorite.
 Clay may have provided the
foundation for first organic
compounds.
 Mineral crystals in clay
could have arranged organic
compounds into organized
patterns.
Ice Earth
 3 billion years ago ice might
have covered the oceans.
 Protected from UV light, organic
compounds may have formed
and reacted with one another.
HOW DID CELLS FORM?
Sidney Fox and other scientists have done extensive
research on the physical structures that may have given rise
to the first cells.
 Cell like structures, including microspheres and
coacervates, form spontaneously in certain kinds of
solutions.

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
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Coacervates and microspheres like cells can take up certain
substances from their surroundings.
Coacervates can grow
Microspheres can bud to from smaller microspheres. However,
microspheres and coacervates do not have all of the properties of
life.
Unlike cells, microspheres and coacervates do not have hereditary
material.
WHEN DID ATMOSPHERIC OXYGEN
APPEARED?
 About 2.7 b.y.a., cyanobacteria or
blue-green algae began
photosynthetic reactions
 About 1.8 b.y.a, the atmosphere
contained abundant free oxygen.
Allowed for the development of
more complex, oxygen-breathing
life forms
Caused the first mass extinction of
organism that had evolved in an
oxygen-less planet
Ended the process of chemical
evolution
Spirulina
HOW DID THE FIRST EUKARYOTES FORMS?
According to the endosymbiotic
theory, eukaryotic cells formed
from a symbiosis among several
different prokaryotic organisms.
 Eukaryote provided a beneficial
environment
 Prokaryote provided a method of
energy synthesis.
 Did not receive much support until
the 1960s, when it was championed
by Lynn Margulis of Boston
University.

Aerobic
prokaryote
Anaerobic
eukaryote
WHAT EVIDENCE SUPPORTS THE
ENDOSYMBIOTIC THEORY?
Mitochondria and chloroplasts contain DNA similar to bacterial
DNA.
 Mitochondria and
chloroplasts have
ribosomes whose size
and structure closely
resemble those of
bacteria.
 Mitochondria and chloroplasts, like bacteria, reproduce by
binary fission.
 Mitochondria and chloroplast replicate independently from the
replication cycle of the cells that contains them.

WHAT IS THE ESSENTIAL QUESTION?
Scientists explain that that life arose from nonlife
billions of years ago through the theory of
abiogenesis.
Could life arise from nonlife today? Explain.