8-13 Flashcards
privide an outlife of life on earth time line
first 2 billion years - we know nothing
next 2 b, life was microscopic microbes, rarely larger than 1mm or 2-3 cells
following 600 m years to presentm explosion of large and complex organisms - cambrian explosion
what was the cambrian explosion
explsion of life
545 million years ago
development of life in 5-10 m years in short time frame
led to most animal groups development that we know today
What does intermezzo mean
diversity and complexity
what does morph mean in evolution
the incormpoation of a modular construction of standardised units to form a dynamic range of sizes
What are the levels of organisation
Cell
tissue
organ
organ system
organism
What are the 3 domains of life
Eukaroyta
Bacteria
Archea
What are prokaryotes
Bacteria and Archaea
- 2 domians of single cell organisms
- they are cell without a nuclei and consist of a long strand of DNA with several thousend genes
How many species live on earth todat
10 million
what are eukaryotes
multi celled organisms have a nucleeous, seperated by a membrane
DNA held within the nucleus
Eurkaryotes can store more infomration in their genetic material
Morphological evoltuion allowed…
Allowed increase in size and therefore complexity
More complexity means more diversity
What are the mechanisms for evolutionary processes
- random passive tendancy t evolve through an overall increase in variance
- non random, active, process that bisas evolution towards increased size of comeplexity
What evidnce is there from the fosil period
multi-celular life evoved independantly many times
life forms with new body parts or morphology (higher comeplxity) arise from early multi-cellular organsisms
New life forms lead to periods of rapid diversification
What are cyanobacteria
What are stromatolites
rock based structures built by microbes (single celled cyanobactria) know as blue-green algae — sharks bay
what are trilobites
one of the oldest know fossil groups - 500 m yrs old
they roamed the oceans for 270 million years
What is life made from - gimme the ingrediants
83 stable elements - 4 (H, O, C, N) weigh 95% of all living matter
What is the utillity of hydrogen and oxygen
follows from the large amount of water that make living oganisms
what is the utillity of carbon
has good abillity to bond with other carbon atoms - creating chains and bonds with other atoms
what is the utility of nitrogen and oxygen
capable of forming bonds with carbon that are robust but not unbreakable — a combination of carbon, oxygen and nitrogen bonds can exist
What are expremopiles
microorganisms that thrive in extreme envrionments (from HUman perspective)
Many of them could not survice in moderate condictions
What are the categories of extreame environment
PHysical
Geogchemical
Biological
What is the atmoushphic pressure at sea level
100,000 Pa or 1.01 bar
What are some environmental limiting
Temp, radiationn, salinity, pH, desiccation, pressure, oxygen
What are thermophiles
50-80 degress
what are mesophiles
15-50 degrees
What are psychrophiles
less than 15 degrees
What are tardigraades
water bears
they show crypotbosis
they disiccatie as environment dries
they shrivel into a tun and wait for mositure to return
1150 species discovered since 1773
only grow to 1mm
they have 4 pairs of each limbs
What is extreame
a distance from the median for that ecosystem variable
Why is temprature important for enzymes
They have optimal ranges for energy - too cold = frozen, too hot = protein and nucleic acids break down
What is the highest temprature surviving domian of life -
archeae
What is sulfolobus acidocaldrius
survives with average pH of 3 and temp of 80 dgerees
How deep is the marian trench and what is the pressure there
10994 (6 way)
pressure of 1086 bars - more than 1000 x that of sea level
What is the challenge of pressure on life
cell membranes are compressed - decreases mebranve fluidity and prevents many chemical reactions
How does pressure change in the atmoussphere
10km above SL, 1/4th pressure
What role did oxygen play in early life ?
it was an anaerobic environment - photosinthisis oxygen increased in the atmpoushphere
What role does oxygen play in life today
key element to sustain life - photosinthisis and respiration
How does oxygen damage things
Oxidation = to nucleic acids, priotiens and lipids
(some things have evolved to have antioxidents)
What is the environment on mars
Surface temp - 210 K
Atms pressure - 0.007 bars
Atms make up - 95% Co2
Gravity - 38%
It also has high solar raditation levels
What is the environment on Venus
Surface temp - 737 K
Atms pressure - 92 bars
Atms make up - 96% Co2 +suphuric acid clouds
Gravity - 88%
What are the key requirements for life
Carbon
Liquid water
energy soruce
WHat is the traditional view of forming life
spontanrous formation of complex molecules from atmouspheric gasses - abiogensis
These molecules accumlate in pools of water under the action of some soild catalyst – life started in this primordial soup
Where has the theory of some little warm pond shifted to
around the areas where there are undersea colcanic vents
What was the miller-urey experiment
1950s
they took molecules they belived to represent major components of the earlyths warlu atmousphere and put them in a closed system
They use:
- Methan
Ammonia
Hydrogen
Water
They ran elecrical curent through the system
What were the results of the Miller Urey experiment
at the end of the week, 10-15% of carbon was now an organic compound
2% of the carbon had formed some amino acids to make protiens
It showed that the organic compounds could be made easily under conditions in early earth
Why was carbon importantg
can form with many other atoms
can dissolve in water
Why is silicon not an altertive to carbon
its bonds are too weak
interacts with too few elements
only form single bonds
;ess mpbile
1000x more abundant on earth, but life is still carbon based
Why is water important in life
living systems need a medium to discolve and for chemical reactions to take place
it is a stable temprature
alternative is ammonia but only liquid when less than -30 degrees
What are some sources of energy
Light - 20-30% weaker than today
impacting sub atomic particles
shock waves
geothermal heat
eruptions of lava
radioactiviuty
thunder and lightning
ocean surf
What is panspermia
idea that life floats about in the interstellar medium and occasionally comes to rest on a planet
space is hazardous though
the building blocks of life could exist in space and then form part of the early atmpushephere
What are some differnt types of Panspermia
Basic - bacterial spores
Radio - propegated by raditaion of stars
Ballistic - cells escape a planet from an impact
Modern - comets
Pesudo - comeplex organic coumpounds from space
Directed 0 intelligent life sent by aliens
What are some more radical theories of Pansperia
viruses and DNA can survive in space and abiogenesis happened close to the galactic cnetrer before paspemia caried life through the glaxcy
What are problems with the alterntive theories of begininngs of life (Hoyle-Whckramasinghe)
opposed idea that life began in a warm soup
There was a sociological preblem between biologists and astologers as the two disiplines never meet
What if Hoyle and Wichramasinghe are correctg
bactria could be around interstellar clouds that collapse to form stars and planets
comets could preseve lifeforms and scatter tham to other planets
supported by e.coli data
how could comets contain life
Theybhave frozen water, dust and other substances
anaerobic bacteria dont need oxygen to grow
they shower viable material onto planets like earth
what life was there in Hale-Bopp
infrared raditaion emmited by small particles in the coma of HB
What is the rate of arrival of material on earth
100 tons per day
may bring new bugs which could interact with terestial life or kill it
whaqt role does UV radtion play in preventing life from traversing the solar system
only 0.1% of bacterial spores survived 2,500 yrs of UV starlight - if coated with 1 micron of dust or soot, they would be shieled
Why is a TV camara important to finfing extreame survival in space
it had stretococcus mitis on it after 2 years in space because someone had sneezed on it before it went up and it survived
We now know that vacum is not a fatal problem for bacteria
What is in the space inbetween stars
around one H atom per cubic meter
they are heated by UV radiation so move very fast and bonds are hard to make
What are GMCs
Giant molecular clouds (hard to make) - they are the sites of star and planet formation
How large and how long do GMCs last for
150 ly across, 10 -100 million years
How to GMCs help facillitatet life
they contain grafite dust to shield UV light and acts as a catylist
we cannot recreate them becase we cant get the desnity low enough or wait millions of yearsWh
What are most of the molecules in GMCs
hydrogen
CO
How are molecules detected
MASEERS
Microwave amplification by stimulated emission of radiation
Like lasters
How are moelcules detercted from earth
ALMA telescope - atacama large milimiter array - very high and dry location - observes in mm and sub-mm wavelengths
When have molecules been found in space
OH in 1963
Ammonia in 1968
CH20 in 1969
What are the four types of organic molecules that combine to build cells and their parts
carbohydrates
protiens
lipids
necleic acids
What is the amino acid glycine
formed from a reaction between acetic acid and ammonia
What is Glycoaldehyde
a simple sugar that forms one of the subunits of nucleic acid
What was the murchison meteroite and why was it imporant
landed in 1969
weighted over 100kg
one of the most studied meteorites
7 billion yrs old
(oldest on earth)
had common amino acids like glycine, alanine, glutamic
Equal amount of L and D types of amino acids
What is chirality
mirror symmetry
amino acids exist in two forms, mirroring each other in L and D types - all life on earth uses L types - D types can be produced in labs
How do we define a habitable planet
Liquids - medium for molecules to dissolve and chemical reactions take place
Suitable Star - energy
Atmoushphere - sheilfds radiation, temp, chemicals
Gravity - keep atmoushpehre bound to planet
Jupiter - protector from asteroids and comets
Moon - tidal and climate
What are the chemical elements required for life
Carbon
H
O
N
Mg
Ca
Cl
What would happen if the temprature is too high in planrt
the mositure wil evapourate into space or create a greenhouse effect –
venus - runaway GHE - the surface as dried up and riased temps to 460 degrees
What happens if the temprature is too low in a planet
too little solar heat can lead to permanent ice age
snowball earth scenario - aldedo of the earth inensifies coolding
what is the snowball earth
scenario where ice formations leafd to albedo and mroe cooling after solar radiation is reflected back into space
what is the circumsetllar habitale zone
the areas around a star which can support liquid water - 273-373
Why do the moon and mars not have enoguh gravity to support life on earth
moon - not massive enough to hold atmpusphere - onlu 1/6th of earths
Mars - 62% lower gravity than on earth - only a thin layer of CO2 provides little insulation. solar wind is stripping away martian atmpouhssphere
Where are tghe heavy elemetns found
Heavy elements are found in all population-I type stars (younger, second generation) but not in enough quantity in older population II stars
the older stars are found in the centre of our galaxy - they are unlikley to have rocky planets and so are likley devoiud of any life
How was the first atmoushphere formed
outgassing of gases trapped in the interior of the early earth
How large is the milky way
80,000 ly across
what is the milky way buldge made from
old stars, gas, dust
what does the MW disk contain
young stars, gas and dust - concentrated in spiral arms
what does the halo in the milky way conatin
old stars and clusters of old stars, dark matter
what is andomeda
our sister galaxy
2.5 million yr away
What is eccentrcity and why is it important
one feature of our solar system is that it is less elliptical than others of similar size and shape
The prevents plunges into the inner galaxy where radiation and super novae are commin
What is co-rotation
where the angular speed of the galaxy spiral meets that of the stars within
What is metallicity
the abundanmce of other elements apart from hydrogen and helium
how does metallicity vary in different stars
less than 0.1% in old stras
more than 2% in young stars in the galactic disk
a high volumne of metals is important for the creation of rocky planets §
How many exoplanets have been found with a metallity of less than 20% solar
7 exoplanets, all gas giants
What would happen if metallicity is too high ?
terresrial planets would be larger with stronger gravity, richer in volitile compounds
they would probably be covered in water
thought to be bad for weather
what is a parsec (pc)
3.261 light years
1 kiloparsec = 3261 ly
How does the metrallicity of the gas in the mily way vary
at the suns location, (8kpc) from the centre, the metallicity is falling at 17% per kpc
Summerise the trade offs in galstaic planet survival in thr galaxcy
too far - supply of materials is too poor
too close - inner regions have high supernovae - likley to be exposed to radiation
What is the GHZ
galactic habitable zone
What are active galactic nuclei
Areas at the centre of some galaxcies that is brighter than can be explained
what on our planet defends particle radiation
planets magenetic field
what on our planet screens out electromegnetic radiation
ozone layer
What is the killer radius of a SN
100 ly
where do most supernovae take place
60% of the suns distace from the cenrrew
how oftern do SN happen
6 in past 1000 years
1 per 40 +- 10 year in normal galaxcies
What are gamma-ray bursts
most powerful explosions observed in distant ga;axies since the big bang - they could sterlise earth in one shot
Would remove the ozone layer and allow SOlar UV to reach the earth
Gamma rays pass thoguh humans and ionise things, causing tissue damage and DNA
How habitable are globular clusters
low metallicity
How habitable are Nebulae
newly formed giant stars with strong winds ould evaportae protoplanets
How habitable are Nebulae Trifid Nebula
Ionised gas hazad affecting the atmoushphere
How habitable are massive young stars
lots of UV and short livesx
How habitable are galactic centre
intense radiation and unstabel orbits
How habitable are supernova remnants (cygnuslooop)
debris from stellar explosions
