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
