lec 2- cosmology 2 Flashcards
how many natural elements are there and what are the most abundant elements in space?
-92 elements
-most abundant are hydrogen and helium, with trace amounts of lithium beryllium and boron
how are all the heavier elements like carbon formed?
by the process of nuclear fusion reactions in hot stages of stars (process called nucleosynthesis)
when does nucleosynthesis stop in most stars?
with the formation of iron, core cools and gravity causes implosion and heating
how do elements heavier than iron form and enter the rest of the space?
elements heavier than iron only form under extreme heat at the core of massive stars, and are then scattered into space from supernova explosions
how do new stars and solar systems form?
pre-existing dust clouds capture elements with the help of gravity, creating a molecular nursery that leads to their formation
what are stellar nebulae?
cosmic gas and dust clouds
how did our solar system form?
gravity condenses dust clouds with elements, creating the solar system
what are the three major transitions in evolution?
- need to get replicating molecules into protocells
- need to bind independent replicators into chromosomes
- then need to evolve a full prokaryotic set of machinery
in what time interval was there no life?
4.6-3.8 bya
during what time did life originate?
3.8 bya onwards
what was the eon of no life called?
the Hadean eon
what was the conditions of earth during the Hadean eon?
hot and bombarded by comets and asteroids (very unsuitable for life)
what was the eon of first life called?
early Archaean eon
what is the proper definition of life?
life: carbon based, membrane bound structures with controlled energy conversion using ATP, ability to reproduce with variation to be able to evolve and adapt
what are the 3 steps needed for life?
- the origin of biological monomers
- the origin of biological polymers
- the evolution from molecules to cells
what are the three hypotheses behind the origin of life?
- created in prebiotic soup
- arrived on meteorites, life itself (panspermia) or building blocks
- created in deep sea vents
what are the three abiogenesis hypotheses?
- RNA first then cell membranes
- Metabolism (macromolecules capable of energy conversion) first then membrane
- Membranes first: protocells containers trapping other molecules inside including RNA
what is the RNA world hypothesis?
-RNA stored both genetic info and catalyzed reactions
-then overtaken by DNA
what is the primordial soup hypothesis and the three steps?
-Oparin and Haldane hypothesized that all the building blocks for life are located in a liquid where they eventually all combine and mix together to create life
1. assemble molecules into building blocks for polymers
2. assemble polymers
3. add membranes and energy source to make a living organism
what did Miller and Urey do?
created an experiment where they recreated the environment of early Earth and tested if amino acids could be made
how many different amino acids were found in Miller and Ureys test tube after many years since their experiment?
over 20 which is more than the amino acids found in current life
do amino acids also form in space?
yes, on comets and meteorites
what are the 4 ideas on earth early atmosphere according to Miller and Urey?
- earth had a reducing atmosphere with no free oxygen, ammonia, or methane. Had a lot of carbon and nitrogen
- this atmosphere created organic compounds (monomers) in water after reacting with energy like lightning, heat, or radiation
- Monomers are than accumulated in the diluted organic soup
- the monomers then polymerize into polymers and turn into life
what did Sidney Fox find out about amino acid?
when amino acids are dried out, they form proteinoid microspheres
what did David Deamer propose on life’s origins?
-that it originated in hydrothermal pools
-layers of lipids build up on edges of the pool, trapping chemicals and encouraging the growth of RNA molecules, Lipid bound droplets would then peel off, creating RNA filled proto-cells
are processes of self assembly in nature common?
yes, like snowflakes, protein folding and more.
