The Mechanism and History of Life

Hannah Cebulla, Nikoli Brown, Katherine Lee, Nate Johnson,

Jeremiah Hashley, Brett Gordon

Earth’s Early Chemical Composition

Pre-Earth-Protoplanetary disk

-Roughly the mass of Jupiter

-Heavier elements are closer to the Sun

-Silicate dust and ice

-H

2

, He are the dominant gases

-99% gas

Williams, Jonathan P., and Lucas A. Cieza. "Protoplanetary Disks and Their Evolution." Annual Review of Astronomy and Astrophysics (2011):

67-117. University of Hawaii Institute of Astronomy. Web. 11 Nov. 2016.

4.6 billion years ago-Core accretion model

-Differentiation

-Moon formed

-Dominant elements: Fe (320,400 ppm),

O (316,700 ppm), Mg (148,600 ppm), Si

(145, 900 ppm), and Ni (17,200 ppm)

-Most oxygen bound up as oxides rather

than as O

2

Kargel, J. S., and J. S. Lewis. The Composition and Early Evolution of Earth. N.p.: Icarus, Sept. 1993. PDF.

4 billion years ago-The Late Heavy Bombardment ends

-Oceans form

-Atmosphere forms

-Most prominent chemicals are H

2

O (2699 ppm), C (526 ppm), and N (1.68 ppm)

-Atmosphere comprised mostly of H

2

, H

2

O, NH

3

, CH

4

, and H

2

S

Marty, Bernard. "The Origins and Concentrations of Water, Carbon, Nitrogen and Noble Gases on Earth." Earth and Planetary Science Letters

313-314 (2012): 56-66. ScienceDirect. Web. 11 Nov. 2016.

3.5 to 4 billion years ago-Organic molecules originate

-Miller-Urey experiment

-differing origin theories

-Most important molecules for life: C, H

2

O, N, O, PO

3

Sagan, Carl. Cosmos. New York: Random House, 1980. Print.

3.6 billion years ago-Life starts

-Organic carbon discovered in ancient

lava

-May have begun around deep-sea

hydrothermal vents

-Simple, single-celled organisms

-Doesn’t use O

2

Furnes, Harald, Neil R. Banerjee, Karlis Muehlenbachs, Hubert Staudigel, and Maarten De Wit. "Early Life Recorded in Archean Pillow Lavas."

Science 304.5670 (2004): 578-81. Science. Web. 12 Nov. 2016

3.4 billion years ago-Photosynthesis...ish

-Not photosynthesis in its modern sense

-Convert energy from the sun into

energy for the cell

-Still no oxygen

-Probably didn’t use water

Blankenship, Robert E. "Early Evolution of Photosynthesis." Plant Physiology 154 (2010): 434-38. Web. 12 Nov. 2016.

3 billion years ago

-Plate tectonics puts N

2

into

atmosphere

-Nitrogen is very important for life

-Evidence: transition from mafic to

felsic rocks

Tang, Ming, Kang Chen, and Roberta L. Rudnick. "Archean Upper Crust Transition from Mafic to Felsic Marks the Onset of Plate Tectonics."

Science 351.6271 (2016): 372-75. Web. 13 Nov. 2016.

2.4 billion years ago-Great Oxidation

-Cyanobacteria: first real photosynthesis

-Drastically changes the composition of the atmosphere: less CH

4

, far more O

2

-First mass extinction

-Leads to the first snowball Earth (~2.2 billion years ago)

Sessions, Alex L., David M. Doughty, Paula V. Welander, Roger E. Summons, and Dianne K. Newman. "The Continuing Puzzle of the Great

Oxidation Event." Current Biology 19.14 (2009): R567-574. ScienceDirect. Web. 13 Nov. 2016.

The Definition of Life on Earth

Criteria of Life

● Homeostasis (resistance to change)

● Metabolism (taking in energy)

● Organization (one or more cells)

● Reproduction

● Response to stimuli

● Growth (increase in size, not just accumulation)

● Adaptation (needed in process of evolution)

Exceptions to Definition The large gray area in the definition of life:

Viruses

When in contact with host:

■ Active

■ Can reproduce when host

is “infected”

■ Reacts to environment

■ Behaves like a living

organism

Without contact with host:

■ Dormant, inactive

■ Cannot reproduce or

replicate itself

■ Static organic particle (these

are known as Virions)

■ No internal biological

activities

CrystalsExhibit many of the characteristics of living things:

● Growth

● Take in energy by chemicals

● Response to stimuli

● “Adapt” to environment

But it doesn’t have a nervous system and can’t reproduce

Its growth is accumulative, not increase in different parts of organism

Why life on Earth is unique

Life depends on the characteristics of Earth

● Orbits the sun (a star of a certain size)

● Orbits at a certain distance (and is almost circular in orbit)

○ This determines the temperature (along with the atmosphere on Earth)

○ Covered in liquid water (needed for life)

● Within the considered “habitable zone” around the sun

● Temperature is within a certain range for living

○ Spin of Earth contributes to constant temperature

Life outside of earth (what we look for)We look for another earth

Same characteristics of earth that

could support human life.

Water and atmospheres

Habitable zones around a star (one

similiar to the sun)

But what if life outside of Earth

looked completely different?

Kepler-186f (one of five planets in system)■ Similar size to Earth

■ Within habitable zone of

Kepler-186 System

■ Composition is most likely to

be rocky

■ 490 light years away

■ Orbit of about 130 days

around red dwarf star

We are looking for earth-like planets

which means earth-like life.

Microbiologist “Venkat”

Experimenting with life in space (fungi and bacteria) and how space affects life

Samples sent on SpaceX Dragon Capsule with two microbial tests

Microgravity effects on tiny organisms

Detected radiation-resistance bacteria

Work shows

● Effects on astronauts in space (health)

● New compounds for radiation therapy and cancer treatments

● what kinds of life can survive in space and on planets with different compositions

and atmospheres

Abiogenisis Inorganic Matter -----------> Living Things

What Does Life Need?Energy

Water

Safe Environment

Variety of Chemicals

EnergyActivation Energy

Gibbs Free Energy Equation

Ex. Micelle

∆G=∆H-T∆S

Liquid WaterGreat Solvent

-Acts as Acid and Base

-Holds ions

Ex. Miller-Urey Experiment

Safe EnvironmentProtection from radiation

Protection from collisions

Ex. Life by land and by sea

Important ChemicalsMeteorites

Rocks and Minerals

Iron

How to Find the Origins of LifeBottom Up or Top Down Approach

- Place chemicals and conditions to create life (Miller-Urey)

- Look at life and work backwards (Craig Venter)

Metabolism

Breaking and building molecular bonds

Using energy of one reaction to power another reaction

Ex. Iron and Clay provide surfaces for the reactions to take place

Replication: Finding LUCA355 genes common to all life on earth

Genes produce a CO2 and N2 fixing with H2 dependant and thermophilic.

Metabolism Vs. Replication Modern Chicken and Egg

Most people believe that metabolism was first

Provides and environment for replication to occur

Ex. http://biochemical-pathways.com/#/map/1

So What Happened? What Do We Know?Earth forms from basic chemical compounds

Earth cools, allowing for deep vent formation T=100-150C

Basic Elements form chemical monomers ex. Amino Acids etc.

Chemicals attach to surface creating specific environments

These environments localize metabolic processes

Metabolic process provide environment for RNA replication

All processes contained in cell wall

The Theory of Evolution

What is it? A quick summary

The theory of evolution by natural selection is the process in which organisms change

over time as a result of changes in heritable physical, or behavioral traits.

All organisms are thought to have a common ancestor as well!

“It is not the strongest of the species that survive, nor the most intelligent, but the one

more responsive to change.” - Charles Darwin… Who is he?

Charles Darwin (1809-1882)Went to the galapagos, and saw something strange…

Various species of finches that varied from island to island

WHY!?

Wrote his book The Origin of Species when a majority of the world believed in some

form of “Creator”.

Natural selection and adaptations. Natural selection is essentially an organism's ability to survive in various conditions,

and to successfully reproduce.

Adaptations are when an organism changes to be better suited to its environment

usually driven by mutations.

The craziest example of this, are whales!

Let’s draw an example

Evolution Telephone

So for those of you that couldn't follow my drawing, we have a classroom activity to try

out.

Evolution today.Peppered moth story

End

The History of Life’s EvolutionBrett

By the end of my section you should be able to● Understand the basic timeline of life on Earth

● Understand the basic timeline of the geology of Earth

● Know why extinctions were important for biodiversity

● Evaluate what your favorite looking animal was of all of history.

● Be able to find one TRULY cool fact per slide

Major Events overview● Life Started (3.7 BYA)

● Photosynthesis (3..7-3.4 BYA)

● Plate tectonics (3 BYA)

● Oxygen Atmosphere (2.4-1.6) BYA)

● Multicellular Life (2 BYA)

● Endosymbiosis (2-1 BYA)

● First Sex (1.2 BYA)

● Shell animals (535 MYA)

● Plants on Land (465 MYA)

● Mass Extinction #1 (460 MYA)

● Sea to land animals (375 MYA)

● Devonian Extinction (375 MYA)

● Reptiles (320 MYA)

● Pangea (300 MYA)

● Permian Extinction(252 MYA)

● Mammals (220 MYA)

● Triassic Extinction (201 MYA)

● Feathered Birds (160 MYA)

● Flowers and Grains (130 MYA)

● Death of Dinosaurs (65 MYA)

● C4 Photosynthesis (32 MYA)

● First Hominins (13 MYA)

Life starts (3.5 Billion Years) ● 3.5 billion years old

○ Confirmed by fossils

● Stromatolites (microorganism mats)

○ Energy from sun

○ In the water

○ Rocks and matter found in crust

● NO plate tectonics at this point.

● How old is this?

○ 3.5 BYA-.201 BYA

■ =3.29 billion years before ‘Titanic

Dinosaurs

■ Stack of 1 billion dollars

● 67.9 miles

● How do we know?

○ There was life, but there was no O

2

deposition clues.

○ Deep sea vents hold bacteria that live off of

sulphur and hydrogen reduction

Photosynthesis-ish (3.7-3.4 BYA)● No modern photosynthesis

● Just used the sun to reduce (gain electrons)

and store energy in bonds

○ Could have been iron, or anything to

conduct redox reaction

○ Thought to be hydrogen and sulfur, NOT

water

1937, Robert Hill discovered plants can

4 Fe

3+

+2H

2

O → 4Fe

2+

+ O

2

+ 4H

+

Plate Tectonics!! (3 BYA)● Puts nitrogen into the atmosphere!

○ Recycling of rocks

● Not totally for certain on time.

● Soaks up CO

2

● Why is Nitrogen important?

○ DNA

○ RNA

○ Proteins and peptide bonds

Evidence?

● Coolest one: Paleomagnetism

○ Magnetite in lava rocks point north when

cooled.

○ All basalt doesn’t point in the same direction!

○ Poles are assumed to stay at axis

●

The Great Oxidation Event (2.4 BYA)● Bacteria began to photosynthesize!

○ Again? (Oceans were full!)

○ CO

2

and H

2

O this time

● Made “Snowball Earth”

○ Just enough crust showing to continue life

○ Caused by O

2

stripping Methane from

atmosphere

● How do we know?

○ Iron Oxide precipitation in oceans

○ Means oxygen saturated water, and began

staying in atmosphere

Endosymbiosis (2-1 BYA)● What is it?

○ Cells eat other cells!

Like eating a chef and they are always being

there to cook!

● What is the evidence?

○ Mitochondrial DNA is more closely related

to bacteria than parent cell!

● Not readily accepted until 1960’s!

● Why is this important?

○ Allows ‘us’ to make ATP

○ Allows plants to make sugars

○ Helped life become complicated!

Multicellular Life (2.1 BYA)● Cells of same code become organized

● Why is this important?

○ Bigger container

○ More organization

○ Allows resilience!

● Evidence

○ Shale found in Gabon of ‘centimeter-sized structures interpreted as organized and spatially discrete populations of colonial organisms living in an oxygenated marine ecosystem.

○ Extremely rare in the fact that all other rocks of this age “ have experienced thermal overprinting from burial diagenesis and metamorphism, [these samples] have not.”

○ Last evidence was 575 million years ago

First Sex (565 MYA)● It was very special? Nah...

○ They didn’t catch feelings

● Sponge like creatures in ancient oceans.

● My theory: Mutation in DNA synthesis and

the rest might work?

● Why is it important?

○ Creates increased rate of evolution

○ Genetic variety for multicellular

○ Red Queen hypothesis

■ “I don’t wanna shmang, you and your

whole family sick all the time”

● Evidence?

○ F. dorothea in 2005 (see left) in Australia

○ (back at it again with Earth’s History)

Ordovician Extinction (444 MYA)● What caused the extinction?

○ Ice age from CO

2

being sucked by new rocks

○ (remember tectonics!?!)

● What was there: Sea Creatures

○ Graptolites

■ Filter feeders

○ Trilobites

○ Conodonts

■ Toothy invertebrates

● Left room for FISH!

The Great Dying aka Permian Extinction (252 MYA)● What caused it?

○ Volcanos created Greenhouse effect

○ Methane released by microbes in response

○ Oceans acidified

● 96% of ocean life died

○ 300 million years wasted

● 50% land life died

● What was there?

○ Marine invertebrates

○ Ferns

○ Synapsids (mammal-like reptiles)

● Who filled the gap?

○ Dinosaurs!

○ Seed plants!

■ conifers

Triassic Extinction (200 MYA)● What caused it?

○ Debated

■ Pangea rifting led to warming

■ Methane release from mild warming

■ Asteroid

● Who was there?

○ Dinosaurs

○ Marine reptiles

○ brachiopods

● Who filled the gap?

○ More dinosaurs! (Jurassic Park)

Cretaceous Extinction (65 MYA)● What caused it?

○ Most likely Asteroids

■ Made earth real dark

■ No more photos please!

○ Could also be more plate tect

● Who went extinct?

○ Dinosaurs

○ Marine invertebrates

○ Crocodiles

○ Ancestors of modern birds

● Who filled the Gap?

○ LIttle mammals

○ Plants of today!

Alternative Life Forms

Extremophiles● Defined as organisms that thrive under extreme conditions

○ Microbes thrive in conditions that would terminate humans in seconds

● The term is generally used to describe prokaryotes but can also be used to

describe bacteria and archaea

● Most extremophiles are microbes

Anaerobic Organisms● An organism that does not require

oxygen for growth

● In some cases, oxygen is actually

toxic to the organism

○ Obligate anaerobes

● Anaerobic organisms do not produce

energy from carbon dioxide, rather,

they metabolize inorganic

compounds

Prokaryotes● Do not require free oxygen to

sustain themselves

○ Not harmed by free oxygen in

their environment

● Single celled organisms

● Lacking membrane bound

organelles

○ Some have chloroplasts and can

respire via photosynthesis

Cyanobacteria

● Single celled

● Survive through photosynthesis

● Generate about 16x more energy than

anaerobic organisms

● Capable of surviving in extremely

harsh conditions

The Oxygenation Event● Responsible for the evolution of aerobic

respiration and the catalyst for the evolution of stable and successful life on Earth

● Proves that the study of extremophiles is important in the search for extraterrestrial life

Snowball EarthSnowball Earth● In a relatively short time

period:○ Oxygen levels

skyrocketed, causing the oceans to be inhabitable to some anaerobic organisms

○ The methane and CO2 rich atmosphere was dominated by oxygen, causing temperatures to drop due to a lack of greenhouse gasses

○ Many scientists theorize that the severity of this event is what caused cellular differentiation

Antarctica● Excellent representation of earth

during its snowball and ice age periods

● Organisms that survive here are not necessarily anaerobic, but can survive extremely low temperatures and a relatively high pH balance

● Colwellia is a type of deep sea anaerobic bacteria that is found in ice samples from Antarctica

○ Similar environments and organisms may be found on other planets

Yellowstone● Thermophiles

○ Metabolic processes■ Photosynthesis

● Occurs in plants, algae, and cyanobacteria

■ Fermentation● Extremely inefficient compared

to aerobic cellular respiration● Oxygen is the most efficient

electron acceptor of the ETC due to its high electronegativity

○ Process of cellular respiration is called oxidative phosphorylation and is about 16 times more efficient than fermentation

Hydrothermal Vents● Form at locations where

seawater meets magma

● Extremely harsh

environment

○ Ejected fluids are full of

elements such as iron,

calcium, and silicon

○ Water reaches up to 700℉

○ Home to numerous

extremophiles