Astrobiology midterm

Solutions of protein/ nuclide acid denaturation:

Heart shock proteins (help stabilize proteins) & A higher GC conetent in RNA sequences (more stable at high temps)

Xerophile

An organism that can grow in extremely dry, desiccating condition. Exemplified by the soil microbes of the Atacama Desert (south America). W_a below 0.8

Hypolith

An organism that lives inside rocks in cold deserts

Acidophile

An organism with an optimum pH at or below pH 3

Likely requirements for life

-chemistry -solvent -substrate -energy -time

How natural selection works:

1) genetic diversity (genetic variation) 2) natural selection (better traits for certain environment; those get passed on) 3) Time

3 theories on the development of multicellular life

1. Grex (formation of a slug from a single amoeba) 2. Syncytium (formation of cells with many nuclei by incomplete cell division followed by membrane formation and cell speciation). 3. Daughter Cells ( a unicellular organism divided, the daughter cells failed to seperate, thereby resulting in a conglomeration of identical cells in one organism which could then specialize).

Processes that could have driven redox contrasts

1. Photolysis in the atmosphere/ocean 2. Magmatic interactions on the sea floor 3. Hydrogen emitted from terrestrial serpentinization when water reached hot ultramafic (komatiite) rock

Gas Chromatography- Isotope Ratio Mass Spectrometry (GC-IRMS)

Info: measure all biogenic elements and isotopic composition

Lamarckism evolution

The idea that an organism can pass on characteristics that it acquired during its lifetime to its offspring.

Differences between autotroph & heterotroph:

Most autotrophs make their "food" through photosynthesis using the energy of the sun. Heterotrophs cannot make their own food, so they must eat or absorb it.

Triggers initiating or enhancing evolution

Mutation through UV light. Spatial isolation. climate change. mass extinction events.

Komatiite

Name derived fro South African River. Extremely hi MgO Very high melting point. calculated eruption temps in exceeding 1600C. High pH in hydrothermal system with lava flows from this due to the high magnesium content.

defense against ROS

SOD (enzyme) catalyszes the dismutation into oxygen and hydrogen peroxide.

Evolution

The process by which organisms change with time such that descendant differ progressively more from their ancestor. Possible because of mutations.

Yellowstone & Iceland

Thermophiles produce bright colors. Descendants of the earliest life forms on earth.

Primordial Soup (abiogenesis)

Thought to be an ocean that contained organic molecules from which life could have formed.

Tubeworm

Utilization of hydrogen sulfide. o Have a highly vascularized, red "plume" at the tip of their free end which is an organ for exchanging compounds with the environment. o The plume provides essential nutrients to bacteria living inside a specialized organ within their body (trophosome) o Have no digestive tract, but the bacteria turn oxygen, hydrogen sulfide, CO2, etc into organic molecules on which their host worms feed.

Recrystallization

When the original skeleton compounds are still present but in a different form, as from aragonite to calcite.

Hot springs

a spring that is produced by the emergence of geothermally heated groundwater from the earth's crust.

Habitable zone

a theoretical shell surrounding a star in which the planet would have liquid water on its surface.

Daughter Cells

a unicellular organism divided, the daughter cells failed to seperate, thereby resulting in a conglomeration of identical cells in one organism which could then specialize

Osmophile:

an organism capable of growing in enviornment with a higher sugar concentration.

Oligotroph:

an organism capable of growth in nutritionally limited environments. difficulties: extremely low concentrations of nutrients.

Halophile

an organism requiring at least 2M of salt, NaCl, for growth

Endolith:

an organism that lives in microscopic spaces within rocks, such as pores between aggregate grains

Piezophile

an organism that lives optimally at high hydrostatis pressure. Common in the deep terrestrial subsurface, as well as oceanic trenches.

Extremophiles:

an organism that thrives under extreme conditions.

Alkaliphile

an organism with optimal growth at pH levels of 9 or above

Black smoker - hydrothermal vents

chimney structures that emit a cloud of black material, consisting of high levels of sulfur-bearing minerals (sulfides)

Metabolisms using Hydrogen

♣ Through water/rock reactions at high temperatures hydrogen was fromed inorganically and available to be exploited by microbial life. ♣ Knallgas Reaction • Probably limited bc of low oxygen concentrations ♣ Sulfate reduction ♣ Methanogensis

cation

loses electrons. has a positive charge.

Places where life could've started

♣ Air ♣ Sea ♣ Shallow seafloor ♣ Near on-land hydrothermal systems ♣ Near deep-water hydrothermal systems ♣ In hydrothermal systems under ice caps ♣ Shallow-water tidal muds ♣ In sea ice

RNA world

refers to the self-replicating ribonucleic acid (RNA) molecules hypothesised to have been the precursors to all current life on Earth.

radioresistant

resistant to high levels of ionizing radiation, most commonly ultraviolet radiation but also includes organisms capable of resisting nuclear radiation.

Alternatives for carbon

silicon and sulfur

Metabolims using reduced carbon & nitrogen

♣ Anaerobic oxidation of methane ♣ Anaerobic ammonium Oxidation • For both, No fossil evidences from the archaean. • Methan & ammonium would have been available at hydrothermal systems. • Sulfate may be limited.

Metabolisms using light

♣ Anoxygenic photosynthesis ♣ Oxygenic photosynthesis ♣ Photosynthesis could have formed via thermotaxis

Chemoheterotroph

♣ Carbon Source- Organic compounds ♣ Energy source= Organic compounds

Photoheterotroph

♣ Carbon Source- organic compounds ♣ Energy: light

Chemoautotroph

♣ Carbon source- CO2 ♣ Energy source- Inorganic chemicals

Photoautotroph

♣ Carbon source- CO2 ♣ Energy source- Light

The problem with microbial fossils

♣ Don't have hard parts ♣ Are extremely small ♣ & have simple morphologies that can be mimicked by nonbiological mineral microstructures

Fast fossilization

♣ Freezing ♣ Desiccation ♣ Anoxic environment with slow bacteria, delaying decomposition. ♣ Tar entrainment

Fundamental questions of astrobiology

♣ How does life begin & evolve? ♣ Does life exist elsewhere in the universe? ♣ What is the future of life on Earth & beyond?

Theories on the first biomolecules starting on earth:

♣ Miller- Urey: Through electrical discharge ♣ Introduction from outer space through meteoroids ♣ Through meteoroid impact energy ♣ At hot surfaces of hydrothermal systems

♣ OTHER EXTREME ENVIRONMENTS

♣ OTHER EXTREME ENVIRONMENTS • Warm deserts: o Water limitation o High temperatures o High UV radiation • Cold deserts o Water limitation o Freezing o High UV radiation • Caves o No light o Isolation from outside nutrition o Sometimes toxic gases • Intertidal zone o Desiccation o Freezing o UV radiation o Change in salinity

Limitations of the definition of life

♣ Some do not replicate ♣ Early Earth-life may have had a stage that did not include DNA type replication ♣ Candidate for life on other planet ♣ Fire, crystals, computer programs (all grow, reproduce, and mutate.)

Hydrothermal vents Extreme parameters:

♣ Temperature gradient from ambient (2 C) to hydrothermal (400 C) fluids ♣ Strong gradients and high concentrations of hydrogen sulfide

Oxygen- the trouble maker

tendency to radicalize, forming incompletely reduced reactive atmospheric species (ROS) which are highly potent oxidants.

pH defined as:

the -log of the H+ concentration in mol/L.

Extremophiles are classified by:

the condition in which they inhabit. Can exist in multiple categories.

Mitochondria:

the key to multicellular animals 18fold increase in production of ATP.

Where a places to find fossils from the Archaean time/

the last places with Archaean crust: Western Australia (3.6-2.7 Ga) & South Africa (3.6-2.5 Ga)

Follow the energy

the need for energy is universal for all life.

Thermophile

thrive at temperatures between 60-80 C

Hyperthermophile

thrive at temperatures between 80-122 C, such as those found in hydrothermal systems.

Hot-vent gastropod

utilization of iron sulfides. o Lives a sedentary life at the base of black smoker chimneys o Has its food convered by scale-shaped sclerites, mineralized with pyrite and greigite o The only animal known to use iron sulfide as a skeletal material o The function of the sclerites remains speculative; they may from a protection against co-occuring predatory gastropods.

Grex

(formation of a slug from a single amoeba)

Theories of how life liked before the first protocell:

- Genes first: RNA WORLD - Metabolism first -LIPID WORLD

Problems with silicon as an alternative for carbon

-Molecule size: has a larger mass & atomic radius= difficulty forming double or triple covalent bonds. Silicones (complex long chains) are more unstable than their carbon counterparts. -Silicon dioxide (quarz): it's a non-soluble solid at temperature range where water is liquide= hard to be introduced into water-based biochemical systems. Product of aerobic respiration.

energy requirments

1. analogous to power (energy per unit time) 2. Analogous to voltage (energy delivered per unit)

Antarctica's Subglacial lakes

150 interconnected lakes under the ice, isolated from the outside world for up to 35 mio years.

Hydrothermal vents

A fissure in a planet's surgace from which geothermal heated water issues. Commonly found near volcanically active palces, areas where tectonic plates are moving apart, ocean basins, and hotspots.

Sulfur as a substitute for carbon

Able to form long-chain molecules. Suffers from high reactivity (spontaneously reacts with water = unstable). Purely theoretical.

Alternative to water: Ammonium

Advantages: -enables numerous chemical reactions -dissolves most organic molecules -capable of dissolving many elemental metals Disadvantages: -only stable in reduced environments -the hydrogen bonds are weaker than those in water ♣ Ammonium biosphere would likely exist at temps & air pressures that are extremely unusal for terrestrial life

Alternatives to water

Ammonium HF Methanol Hydrogen Sulfide Hydrogen Chloride Mixture of hydrocarbons formamide mixture of water & hydrogen peroxide.

Morphology & metabolism of organism

Animals- diverse morphology, simple metabolism. Microbes- diverse metabolism, simple morphology

Solution for cell freezing & membrane stiffness:

Antifreeze proteins (AFP) & increasing liquidity of membranes.

Recordable life started probably in the ________ (__.___ Billion years ago)

Archaean; 3.8 billion years ago

The 3 domains of life

Bacteria, Acrhaea, (both prokarya; Archaea & bacteria have different membranes) & Eukarya

Why is defining life difficult?

Because we do not have a general theory of living systems. We can only define it based on observable properties & we only have one data set.

Hadean

Before life on earth; ♣ "Hell" ♣ Formation of rock, oceans, and anoxic atmosphere ♣ Water possibly originated from degassing hydrated minerals of the mantle. ♣ Salinity was probably twice as high as today ♣ Magma & meteoroid impacts= sterilized the oceans and evaporated all the water into the atmosphere several times.

Candidates for good chemistry:

C, N, O Carbon=good candidate

Spatial isolation

Can lead to the development of a new species

Follow the nitrogen:

Carbon is hard to track in the atmosphere (most carbon is in the crust/mantle; little in atmosphere). Nitrogen is mostly in the atmosphere.

Natural pathways of evolution

Cell division, gene transfer, & sexual reproduction

Difficulties for life at low temperatures:

Cell freezing & membrane stiffness

Study sites around the world

Chile (Atacama Desert) Baja, CA. South Africa (Mponeng gold mine). Yellowstone. Iceland.

What could be different from earth life biochemistry?

Chirality, Alternatives for carbon, non-green photosynthesizer, alternative atmospheres, nonwater solvents, & interstellar dust based life.

How does mutation occur?

DNA fails to copy accurately (usually naturally occurring). External influences can create them too. -can be cause by exposure to specific chemicals or radiation. Causes dna to break down and then the error would occur when the cell tries to repair it.

Mponeng Gold Mine (South Africa)

Discovered an isolated, self-sustaining bacterial community living under extreme conditions almost 2 miles deep beneath teh surface. First microbial community demonstrated to be exclusively dependent on geologically produced sulfur and hydrogen. Does not depend on energy from the sun. ♣ Desulforudis audaxviator

Atacama Desert (CHILE)

Dry, dusty, harsh. Life forms not apparent. Used to test out the sensitivity of instruments intended to search for life on Mars. MOA (mars organic analyzer) tests run here, proving that the instrument could unambiguously detect amino acids. It's able to detect the preference of earth's amino acids for left-handedness.

Key to microbial metabolisms:

Enzymes

Mantras of astrobiology

Follow the water, nitrogen, and energy. Life is based on carbon chemistry, Sun-like stars provide energy.

Anion

Gains electrons Has a negative Charge

Functioning of the Earth System in the Archaean

Higher heat production due to the greater abundance of radioactive elements. ♣ A hotter mantle= more plume volcanoes with komatiite lava flows less vicious than basalt, i.e flowing larger distances. ♣ Sediments were scarce & consisted of erodes volcanic terrain/ volcanic ashes, being magnesium-rich.

Consequences of a meteoroid impact:

Hitting water o Tsunamis, water vapor into the atmosphere o Increase in temperature Hitting ground o Forest fires, smoke & dust into atmosphere o Darkening troposphere: decrease of temperature, slowing down photosynthesis o Increase in CO2, increase in temperatures after settlement of dust.

Likely candidates for good solvent

Hydrogen, Oxygen & water are abundant water=good candidate

Chirality

In known earth-based life- all amino acids in proteins are left handed & all sugars in DNA and RNA and in the metabolic pathways are right handed. • Molecules of opposite chirality have identical chemical properties to their mirrored forms, so extraterrestrial life that uses D amino acids &/or L sugars would be possible.

Evolution can be accelerated by:

Isolation, climate change, & mass extinctions

Methods of life detection

Light microscopy, electron microscopy, raman spectroscopy, gas chromatography

Advantages of water as a solvent

Liquid over a large temperature range. High heat capacity. Large heat of vaporization. Ability to dissolve a wide variety of compounds due to its polarity. Less dense as a solid than as a liquid.

Desulforudis audaxviator

Lives in total darkness at high temperatures by reducing sulfate and fixing carbon and nitrogen. Found in Mponeng Gold mine, south africa. First single-species ecosystem.

Silicon as an alternative for carbon

Many chemical properties similar to carbon & is in the same periodic table group.

prokaryotes

No membrane around genetic material, i.e. no nucleus

3.2 Ga old fossilized microbial mats from South Africa?

Nofke- • Negative 13C isotope ratios of -20.1 to -21.5% are consistent with a biological origin for the carbon preserved in laminae.

Key innovation in the origin of eukaryotic cells

Organelles

Kinetic Isoptope Effect

Organisms prefer to use the lighter isotopic molecules bc of the lower energy "costs", resulting in significant fractionations between the heavier (substrate) and the lighter (biologically mediated product).

Solutions for life at high osmotic pressure:

Osmoprotectant in the cytoplasma & active osmoregulation

Problems of the first cell

Osmotic stress. -solution: ATP driven pumps Phospholipid bilayer only permeable for lipid-soluble nutrients. Solution: transport mechanism for water soluble nutrients.

Chemofossils/ Biomarkers

Past life leaves some markers that cannot be seen but can be detected in the form of biochemical signals

Non green photosynthesizer

Pigment color depends on light spectrum o Chlorophyll on earth plants appears green bc it absorbs mainly blue & red light, reflecting the green light frequency. If the stars for other planets were in a different state than our sun and if the light frequency that reached the planets' surface was different, then the plants on those planets would have also evolved a different type of photosynthetic

Deinococcus radiodurans

Polyextremophile; ♣ Withstand the lethal & mutagenic effects of DNA damaging agents, particularly the effects of ionizing radiation. ♣ Can survive cold, dehydration, vacuum, & acid. ♣ Toughest bacterium ♣ Evidences indicate that efficient repair of DNA damage is, in large part, responsible for the radio resistance. ♣ "marvelous berry that withstands radiation" ♣ does not form endospores and is nonmotile ♣ an obligate aerobic chemoorganoheterotroph (uses oxygen to derive energy from organic compoudns in its environment) ♣ found in habitats rich in organic materials, such as soil, feces, meat, or sewage.

Fossil

Preserved remains or traces of animals, plants, & other organisms from the remote past. most often the arbitrary date of 10,000 years ago.

First mass extinction catastrophe: Rise of Oxygen

Problem: no fossil record on mass extinction and evolution

Difficulties for life at high temperatures

Protein/ nuclid denaturation (loss of 3D structure, function & solubility).

Enzyme

Proteins that catalyze (speed up) chemical reactions without being changed.

Difficulties for life at low pH:

Proton invasion & protein denaturation

Mass extinction events

Provide empty ecosystems for new life-forms to occupy by wiping out large fractions of the previous inhabitants of those ecosystems.

life gains energy through this:

Redox reactions. Electron donor + Electron acceptor (OXIDATION) = Oxidized donor + electron acceptor (REDUCTION)

Atsmophere of the Archaean

Reduced; • Enriched in: o Methane o Ammonia o Carbon oxides o Water vapor o Nitrous oxides o Hydrogen sulfide o Other noxious gases • Depleted in free oxygen

Serpentization

Rock is changed, with the addition of water into the crystal structure of the minerals found within the rock.

Earliest microbial fossils: Schopf vs. Brasier

Schopf thought he found filamentous microbial fossils. Rama measurement confirmed that the fossils were of carbonaceous material. Brasier reinterpreted them as secondary artefacts formed from amorphous graphite.

Organelles

Specialized subunits within a cell that have a specific function, and are usually separately enclosed within its own lipid membrane.

Wächtershäuser's hypothesis

Steps for producing proteins o Produce acetic acid through metallic ion catalysis o Add carbon to the acetic acid molecule to produce 3-carbo pyruvic acid o Add ammonia to form amino acids o Produce peptides & then proteins

pompeii worm

Temperature o The worm's rear end sits in water as hot as 80 C, while the head rests in about 22C o Back is covered in a fleece of bacteria that can also "take the heat" o The worms secrete mucuous from tiny glands on their backs to feed the bacteria. In return, they are protected by some degree of insulation. o Discovered to be chemolithotropic, contributing to the ecology of the vent community.

Alternative atmospheres

The gasses in our present atmosphere have varied greatly. Changes in the gas mixture in the atmosphere impacts the biochemistry & morphology of life.

Arcahean

The rise of life on Earth: ♣ "beginning" ♣ 3.8-2.5 Ga ♣ formation of small continents ♣ reduced atmosphere ♣ water present ♣ temperature lower than today ♣ first life (fossils of stromatolithes) ♣ Recordable life started probably in the Archaean (3.8 Billion years ago) ♣ Atmosphere • Enriched in: o Methane o Ammonia o Carbon oxides o Water vapor o Nitrous oxides o Hydrogen sulfide o Other noxious gases • Depleted in free oxygen

difficulties for life at high radiation

UV light & radioactive radiation cause DNA damage. Solution: repairing enzymes (ex: Photoreactivating enzymes)

______________ & ____________ are the only single variables known to prevent growth & survival of organisms

Water & temperature.

Tardigrades

Water bears ♣ Short, plump, bilaterally symmetrical, segmented organisms ♣ Reproduce via asexual or sexual reproduction ♣ Feed on the fluids of plant cells, animal cells, and bacteria ♣ Likely related to anthropoda ♣ Oftern referred to as "lesser known taxa" of invertebrates ♣ Found in almost every habitat on earth ♣ Considered aquatic bc they need water around their bodies to permit gas exchange as well as to prevent uncontrolled desiccation ♣ Most easily found living in a film of water on lichens & mosses, as well as in sand dunes, soil, sediments, & leaf litter. ♣ Survive extreme conditions: • temperatures as low as -200 °C and as high as 151°C • freezing and/or thawing processes • changes in salinity • lack of oxygen • lack of water • levels of X-ray radiation 1000x the lethal human dose • some noxious chemicals • boiling alcohol • vacuum • high pressure (up to 6x the pressure of the deepest part of the ocean) • in space! o Survive all of this bc they undergo a process known as cryptobiosis ♣ A state in which metabolic activities come to a reversible standstill. Death-like stae. ♣ Can survive dry periods by curling up into a little ball called a tun ♣ Revival typically takes a few hours. ♣ Live tardigrades have been regenerated from fried moss kept in a museum for over a 100 years.

Oldest Embryo Fossils: Xiao v. Bailey

Xiao -interpreted fossils as fertilized animal eggs & evidence for sponge, cnidarian, & bilaterian. Bailey- interpret fossils as ancient sulfur bacteria bc the size matched, able to reductive division, aggregate, mediating phosphorite deposition, high natural abundance, and geological evidence for sulphidic environments.

The Great Oxidation Event (GOE

a major environmental change around 2,400 million years ago associated with the appearance of free oxygen (O2) in the atmosphere. ♣ , readily oxidizeable minerals were no longer available, and atmospheric oxygen began to accumulate- although its levels continued to fluctuate to the present day.

Lithoautotroph:

a microbe which derives energy from reduced compounds of mineral origin.

Ion

an atom with a positive or negative charge

ROS (reactive oxygen species)

can cause genetic degeneration and phsyiological dysfunction. leads to: death & progressive aging.

Metatolerant:

capable of tolerating high levels of dissolved heavy metals in solution, such as copper, cadmium, arsenic, and zinc. Difficulties: Heavy metals denature protein molecules Solution: sulfide production, production of organic compounds for chelation, uptake & accumulation, transformation into non-toxic forms.

Difficulties for life at high hydrostatic pressure

cell membrane looses fluidity and become impermeable to nutrients. Solution: possibly the biosynthesis of polyunsaturated fatty acids helps maintaining membrane fluidity.

Eurkaryotes

cells contain a nucleus with genetic material within membranes

categories of "biomarkers" that help detect past life

cellular remains, textural fabrics in sediments, biological produced organic matter, minerals whose deposition has been affected by biological processes, stable isotope patterns, & atmospheric constituents

Evidence for bacteria in a mars meteoroid

could be a fossil for extraterrestrial life. ♣ Crystallized approx.. 4.5 Ga ago ♣ 2 shock events ♣ residence time on earth: 13,000 years ♣ Igneous orthopyroxenite from orthopyroxenite ♣ Secondary carbonate minerals ♣ Indications for biology: • Magentosome like structures • Carbonate globules as formed by micriobial processes on Earth • Indigenous ploycyclic aroatic hydropcarbons (PAHs)

Xenobiology:

describes a form of biology that is not (yet) familiar to science and is not found in nature.

atomic structure with a negative charge

electron

Eukaryotes probably formed with the _________________ of the ____________cells; forming __________ & ______________

endosymbiosis; Prokaryotic cells; forming mitochondria & chloroplasts.

Astrobiology also referred t as

exobiology, exopaleontology, and bioastronomy.

Biology main targets of study:

extreme environments, origin of life, evolution of life

Trace fossils

footprints & feces

Syncytium

formation of cells with many nuclei by incomplete cell division followed by membrane formation and cell speciation

Astrogeology/ astrogeochemistry main targets:

geology of the celestial bodies to determine their potential to develop & sustain life; geochemistry of celestial bodies to study the chemical processes and reactions that govern the composition of rocks & soils, the cycles of matter & energy & their interaction with the hydrosphere and the atmosphere of the planet; Fossil records

Psychrophile/ Cyrophile

grows better at temperatures 15C or lower. Common in cold soils, permafrost, polar ice, cold ocean water, and in/under alpine snowpack

Isotopes

has a different mass than the element because it has a different number of neutrons

Difficulties for life at high Osmotic pressure

high solute concentrating on outside, low solute concentration inside (shriveling).

Carbon Chauvinism

humans are carbon-based beings and have never encountered any life that has evolved outside the earth's environment, excluding the possibility of all other elements would be considered this.

The oldest recorded microbial metabolisms are methanogenesis, sulfate reduction and photosynthesis. All of them might have started at ______________ systems.

hydrothermal systems

Baja, CA

hypersaline ponds at a salt producing company as their primary field site to study microbial mats.

substrate

large, complex molecules cannot stay suspended in gas. A solid surface is desirable

Enzyme activity is faster with molecules made of lighter/heavier isotopes?

lighter

Where are brine pools found?

mediterranean, gulf of mexico, and the red sea

Most known extremophiles are ________

microbes.

During the Archaean, the world was most likely covered by ________ ______

microbial mats

Obligate Anaerobes

microorganisms that have never developed a defense against oxygen radicals

Adapted organisms in brine pools

not much known. Some bacteria & arcahea with so far unknown metabolisms have been identified.

Why is Carbon Special

o Can bond to itself o Can form long chains o Can form rings

Biomolecules for life:

o Carbohydrates o Proteins o Lipids o Nucleic acids

Astronomy/ Astrophysics Main goals:

o Detect Earth-sized planets o Determine the basic composition of an extrasolar planet's atmosphere and or surface.

Casts & molds

o Form when the original remains of the organism have been completely dissolved or therwise destroyed. o External Mold ♣ When all that is left is an organism-shaped hole in the rock o Cast ♣ If the hole is later filled with other minerals ♣ Duplicate of organism o Internal mold ♣ Formed when sediments or minerals fill the internal cavity of an organism, such as the inside of a bivalve of a snail.

Other ways to form fossils:

o Freezing o Compression fossils (diagenesis) o Biommuration (replacement by overgrowth) o Carbonization (carbon film remains) o Dessication/ mummification o Amber entombment o Tar

Deep Biosphere

o Half of all prokaryotic microorganisms on Earth are found deep down in the seabed (est 500m). o The biomass of sub-seafloor microorganisms corresponds to 1/10 to 1/3 of the total living biomass on Earth.

Permineralization

o Occurs after burial, as the empty spaces within an organism, (spaces filled with liquid or gas during life) become filled with mineral-rich groundwater & the minerals precipitate from the groundwater, thus occupying empty spaces. o Best viewed as the replacement phenomenon at the cellular level.

Replacement/ Petrification

o Occurs when the shell, bone, or other tissue is replaced with another mineral. o In some cases ,happens s gradually and at such fine scales that the microstructural features are preserved despite the total loss of original material

Prerequisites for fossil formation:

o Rare occurrence (most components decompose relatively quickly following death) o Remains normally need to be covered by sediment ASAP

isotope-fractionation

o Remember: elements have different isotopes with different numbers of neutrons, therefore they differ in weight. ♣ Enzyme activity is faster with molecules made of lighter isotopes • Think of ants (enzymes) carrying different sized leaves (molecules with different isotopes). Which would run faster? o Kinetic Isotope Effect (KIE): Organisms prefer to use the lighter isotopic molecules bc of the lower energy "costs", resulting in significant fractionations between the heavier (substrate) and the lighter (biologically mediated product). o ex: stable isotopes used in geochemistry to follow (past) reactions ♣ H ♣ C ♣ N ♣ O ♣ S

Single Cells vs. multicellular lifeforms

o Single- bacterium , amoeba, paramecium, euglena o Multi- animals, nerve cells, RBC's, etc.

Permafrost

o Soil at or below the freezing point of water (0 C) for 2 or more years. o 20% of Earth's land mass o overlying permafrost is a think active layer that seasonally thaws during summer o Thickness of the active layer varies by year and location, but is typically 0.6-4m thick. o In areas of continuous permafrost & the harsh winters the depth of the permafrost can be as much as 1493m in northern Siberia.

Sea ice

o The ice specific ecosystem (briny habitat) includes bacteria, viruses, unicellular algae, diatom chains, worms & crustaceans. o During cold winter months strong gradients of temperature persist in the ice, spanning form -2C at the bottom of the ice in contact with seawater to -35C at its wind-chilled surface. o In winter brine salinities reach 25% and salt begins to precipitate as opaque minerals. o The survival of organisms depends on their ability to prevent the growth of ice crystal in their bodies. o Primary producers in the sea ice

Brine pools

o These pools are concentrations of water having an extremely high salinity as compared to the surrounding ocean, caused by the motion of large salt deposits (evaporates) through salt tectonics. ♣ Methane is often in high concentration in these areas, providing energy by the process of chemosynthesis to creatures which live in the pool's vicinity. ♣ Considered "lakes" within the ocean due to high salinity of the water, which prevents water of lower salinity from entering & creates a distinct surgace & shoreline for the pool.

Interstellar dust based life

o Tsytovich discovered the possibility of life-like behaviors exhibited by dust particles suspended in plasma, similar to conditions in interstellar space o Computer models showed that when dust became charged, the particles could self-organize into microscopic helical structure capable of replicating themselves, interacting with other neighboring structus, & evolving into more stable forms.

Fossilization favors organisms:

o With hard body parts o Those that were widespread o Those that existed for a long time before going extinct

Key properties of life on earth

order, reproduction, growth & development, energy utilization, response to the environment, & evolutionary adaptation

Darwinian Evolution

organisms more suited for a given environment will have a greater chance of surviving and passing their genes on to succeeding generations. "survival of the fittest"

White smokers - hydrothermal vents

ovents that emit lighter-hued minerals, such as those containing barium, calcium, & silicon. Tend to have lower temperature plumes.

Difficulties for life at high pH:

protein denaturation & low H+ concentration outside cell (problem for ATP synthesis)

Atomic structure with a positive charge

proton

Element is based on the number of _________

protons

These atomic structures within the nucleus have roughly the same mass:

protons and neutrons

Extreme parameters of brine pools

salinities up to 20%. Anoxic temp in areas of hydrothermal activities up to 70C.

Primary producers in the sea ice

single celled algae which develop in the lowermost sections of sea ice, often forming chains & filaments. • Important component of the arctic marine food web.

Preservation of _____ _____ is usually rare.

soft tissues

Working definition of life

something that can reproduce & evolve through natural selection

Metabolism

the set of life-sustaining chemical transformations within the cells of living organisms. allows organisms to grow & reproduce, maintain their structures, & respond to their environments.

ALTERNATIVE BIOCHEMISTRY:

the speculative biochemistry of alien life forms that differ radically from those on Earth

Astrobiology

the study of the origin, distribution, and ultimate fate of life in the universe

Water activity

the vapor pressure of water above a sample divided by tht of pure water at the same temperature; therefore, pure distilled water has a water activity of exactly 1. -Can be used to predict the direction of water movement (high to low) - high substances tend to support more microorganisms

Evidence of a giant impact 65 myr ago:

• At this time alos, 15% of the shallow-water marine families were extinct • Iridium (not a typical crustal rock element on Earth) is 100 times more abundant in the crustal rock • Sediments from this time show elevated quartz contents; quartz shock grains are produced during large impacts • Evidences for an impact crater in the Gulf of Mexico (150 KM size)

Sea ice

• Contains brine systems (high salinity) • Organisms o Psychrophiles o Halophiles

Lake Vostok

• Dimensions: o SA: 15,500 km^2 o Coastline: 1,010 km long o Max depth: more than 1200m o Max length: 250 km o Max width: 50km • Has a geothermal vent • Methane hydrates? • Drill for life: o So far, only samples from accretion ice (danger of contamination) o Recovered DNA sequences were most closely related to those of a hydrogen-utilizing thermophile o Geothermal energy input from high temperature mantle processes or tectonic activity may fuel a chemosynthetic community o The technological & logistical issues, together with concerns for environmental protection, make subglacial lake environment challenging systems for scientific study.

Acidic Rivers:

• Form from the interaction of pyrite with water/air • Supported by microbial activity • Organisms: o Acidophiles o Chemoautotrophs

Permafrost

• Frozen soil or sediment • Hosts active, inactive & dead organisms • Organisms: o Psychrophiles

brine pools

• In the oceans • High salinity • Sometimes also high temperatures • Sometimes methane • Organisms o Halophiles o Thermophiles o Chemoautotrophs

Hydrothermal vents:

• In the oceans • High temperatures • Hydrogen sulfide • Reduced metals • No light (depending on depth) • Organisms: o Thermophiles o Chemoautotrophs

Deep Biosphere:

• In the oceans (sediments) & • On land (soil) • Food limitation • High pressures • Organisms o Oligotrophs o Pietzophiles o Thermophiles

Raman Spectroscopy

• Info: presence of organic compounds, pigments, biomineralization • Limits: sometime noisy signals

Light microscopy:

• Info: structure • Limits: morphology only, no chemistry

Electron Microscopy

• Info: structure, redox state, & mineralogy • Problem: invasive sample preparation

Subglacial lakes in antarctica

• Isolated since millions of years • Interconnected • Might have hydrothermal energy soruces • Organisms? o Oligotrophs o Chemoautotrophs

Metabolism first theory

• Key idea of the theory: early chemistry of life occurred on mineral surfaces (e.g Iron pyrites) near deep hydrothermal vents. • Sulfides provide compartment for cells to evolve.

Lipid world (membranes, which later incorporated reactions and RNA)

• Lipid molecules may have inheritable potential & substantial catalytic capacities • Lipids & amphiphillic molecules may have constituted the first systems capable of information storage, inheritance, & selection. • Hydrophillic- like water • Hydrophobic- don't like water o Allows them to self assemble into vesicles and bilayers

Jupiter's moon Europa

• New research suggests that an ocean of water beneath the icy shell might support life o Pumes of warmer water fracturing the surface give access to organic compounds & light for photsynthesis

Hot Springs:

• On land • High temperatures • Sometimes hydrogen sulfide • Organisms o Thermophiles o Photoautotrophs o Chemoautotrophs

ACIDIC RIVERS

• Rio Tinto (red river) - SW Spain o 100 km long o originates in the Sierra Morena Mountains of Andalusia. o Rises in the core of the Iberian Pyritic Belt o Flows generally south-southwest o Reaches the Gulf of Cadiz at Huelva o Extreme properties ♣ Low pH (1.5-3.1) ♣ High Iron (.4-20.2 g/liter) ♣ High copper (.02-.70 g/liter) ♣ High zinc (.02-.56 g/liter) o Why red? ♣ The Iberian Pyritic belt • Deposited in the carboniferous (300-350 Ma) by hydrothermal activities on the sea floor • Tartessans & Iberians started mining in 3000BC • Mining until the 2nd part of the 15th century (Copper, Iron & manganese) • Large scale mining by UK in 19th century • End of mining for copper in 1986 and for silver in 1996. • After being exposed to air & water, oxidation of metal sulfides (often pyrite, which is iron-sulfide) within the surrounding rock & overburden Generates acidity. ♣ Involvement of acidophile microbes • Colonies of bacteria & archeaea greatly accelerate the decomposition of metal ions, although the reactions also occur in an abiotic environment. • These microbes occur naturally in the rock, but limited water & oxygen supplies keep their numbers low. • Acidophiles favor the low pH levels of abandoned mines. o Uses pyrite to make sulfate & H+ ♣ Continues until the pyrite is depleted.

Cyanobacterial stromatolites

• Use water, CO2, & sunlight to gain energy and build biomass. Products: Oxygen & Calcium carbonate (lime) • Layer of mucus forms over mates of cyanobacterial cells • Debris can get stuck in the mucus o Can be cemented together by the calcium carbonate to grow thin laminations of limestone. o Can accrete over time= banded pattern common to stromatolites

o Phototaxis to photosynthesis

♣ 1. Using the Ingra red part of the sunlight for photosynthesis ♣ 2. Formation of pigments for UV protection ♣ 3. Integration of pigments in photosynthesis with visible light.

3 types of life forms found in permafrost

♣ Active ones ♣ Viable but inactive forms that are frozen in suspended animation until things get better ♣ Frozen carcasses of microbes that gave up and died.

Late Archaean Biosphere

♣ Age of microbial mats ♣ Open ocean ♣ Stromatollites ♣ Hydrothermal communities around andesite volcanoes ♣ Lake communities ♣ Coastal sediment s-microbial mats ♣ mid-ocean ridge chemotrophic community ♣ hydrothermal systems around momatiite shields