Origins of life/Astrobiology

Question 1

Use of metagenomics

Answer 1

Analysis of DNA samples to enable cultivation of organisms

Question 2

Examples of multicellularity (5)

Answer 2

Choanoflagellates -> animals
Green algae -> plants
red, brown algae
fungi
Slime moulds, myxobacteria -> fruting bodies

Question 3

Hydrogen hypothesis (4)

Answer 3

Bill Martin
hydrogen-producing bacterium + hydrogen-consuming archaeon
happened before endomembrane evolved
doesn’t explain ribosomes

Question 4

Ways to investigate origins of life

Answer 4

biosignatures
biomarkers
sediments
stable isotope fractionation

Question 5

Name a biomarker

Answer 5

Hopanoids (from bacteria)

Question 6

Stable isotope fractionation

Answer 6

changes of isotope abundance ratios

C-13 is fixed over C-12 during photosynthesis

Question 7

Two views on cell

Answer 7

Information-processing

Energy-generating

Question 8

Theories on cells (3)

Answer 8

RNA world
Proto-metabolism
Inorganic cells

Question 9

RNA world (3)

Answer 9

RNA as both genome and catalyst
some ancient RNA-like catalysts have been found
DNA took some roles of RNA later

Question 10

Proto-metabolism (2)

Answer 10

volcanic vents

Iron, hydrogen, sulphur

Question 11

Inorganic cell sources (4)

Answer 11

Spontaneous lipid vesicles
Clay as aperiodic crystals and scaffolding adsorbing amino acids
Nucleotides = ammonium cyanide, urea
Oparin-Haldane hypothesis: organic molecules = UV, lightning + methane and ammonia

Question 12

Panspermia (3)

Answer 12

Arrhenius
Small gap between late heavy bombardment and cellular life
some organic compounds found on meteorites

Question 13

Mars (3)

Answer 13

too cold
pressure too low
plumes of methane = underground microorganisms?

Question 14

Timeline

Answer 14

3,5 bya = prokaryotes
2,5 bya = oxygen accumulates
2,1 bya = eukaryotes
700 mya = multicellularity
420 mya = plants colonise land