origin of life Flashcards
Bubble theories
Certain molecules spontaneously form bubbles.
would serve to shield hydrophobic regions from contact with water
supports ocean’s edge scenario
Alexander Oparin’s Bubble Hypothesis (1924)
Primary abiogenesis - protobionts allowed chemical complexity to develop
Many different bubble scenarios have been proposed.
no agreement about composition or how the process occurred
In the laboratory, droplets of abiotically produced organic compounds, called liposomes, form when lipids are added with proteinoids and phosphate.
The lipids form a molecular bilayer at the droplet surface, much like the lipid bilayer of a membrane.
Undergo osmotic responses
Store energy as a membrane potential
(voltage cross the surface).
Protobionts:
aggregates of abiotically produced molecules capable of isolating an internal environment different from its surroundings and showing properties of living cells.
Protobionts that formed in the “organic soup” would not have possessed refined enzymes, the products of inherited instructions.
However, some molecules produced
abiotically do have weak catalytic capacities.
There could well have been protobionts
that had a rudimentary metabolism that
allowed them to modify substances they
took in across their membranes.
Hereditary information in Protobionts
RNA genes and their polypeptide products are packaged within a membrane, thus the protobionts could have evolved as units.
Molecular cooperation could be refined because favorable components were concentrated together, rather than spread throughout the surroundings.
Archaebacteria
Extreme-condition prokaryotes
- Lack peptidoglycan in cell walls
- methanogens
- extreme halophiles
- extreme thermophiles
- Thought to have split from Bacteria 2 bya.
Bacteria
Second major group of prokaryotes Strong cell walls Simpler gene structure Contains most modern prokaryotes includes photosynthetic bacteria cyanobacteria
-Stromatolites-fossilized bacterial mats
Photosynthetic
Responsible of Earth’s atmospheric change
Formed in hypersaline areas where other organisms can not survive.
Modern Stromatolites Shark Bay Australia
First Eukaryotic Cells
Eukaryotes probably arose about 1.5 bya.
Internal membrane-bound structures such as mitochondria and chloroplasts are thought to have evolved via endosymbiosis.
Energy-producing bacteria were engulfed by larger bacteria.
beneficial symbiotic relationship
Endosymbiosis
Multiple endosymbiotic events
Responsible of the formation of various unicellular organisms
Green algae lineage
Red algae lineage
endosymbiosis theory
The theory holds that mitochondria, plastids such as chloroplasts, and possibly other organelles of eukaryotic cells represent formerly free-living prokaryotes taken one inside the other in endosymbiosis.
Which are the habitable words in our solar system?
Moon and Mercury are largely dry.
Venus too hot for liquid water.
Jovian planets (Jupiter and Saturn) are gaseous.
This leaves Mars and a few of the moons orbiting the Jovian planets, notably Europa.
What do we mean by habitable?
- earth like ( oxygen, water, dry land, temperature range)
- microbial life could survive a more extreme set of conditions
- common basic requirements are water and stable conditions
What stabilises the climate?
- size- a long term heat source
- stellar evolution: incoming solar energy
- meteor impact rate: could result in climate change
- presence of a large natural satalitte prevents large swings in obliquity
- oceans regulate global temperatures
why has earth got complex life on it
abundant liquid water,
environmental conditions that maintain liquid water
liquid water
influenced by temperature and atmospheric pressure
a simple requirement for identifying habitable planets.
where do planets with a temperature range that could support liquid water orbit?
the “habitable zone”
