Sedimentology and Palaeontology Lecture 9: Major Evolutionary events and the Origin of life Flashcards
Define ‘Life’
Life is the condition that distinguishes living organisms from dead organisms and non-living things.
Specifically, by the capacity to grow, metabolize, respond
(to stimuli), adapt, and reproduce.
What are the three main domains
Archaea, Bacteria and Eukaryota
Define Prokaryotes
Prokaryotes are organisms whose cells lack a nucleus and other organelles.
Two distinct groups: the bacteria and the archaea
Most prokaryotes are small, single-celled organisms with a simple structure.
Define Eukaryotes
Eukaryotes are organism with have a nucleus and other organelles.
All animals, plants, fungi, and many unicellular organisms are eukaryotes.
List the differences between Prokaryotes and Eukaryotes
Prokaryotes:
* Lack nuclei and other
organelles
* Typically unicellular
* Reproduce asexually
Eukaryotes:
* Posses a nucleus and organelles
(e.g. mitochondria)
* Unicellular and multicellular
* Reproduce asexually and sexually
What is the main theory of the origin of Eukaryotes
Endosymbiosis
* Theorised by Lynn Margulis 1967
Organelles such as mitochondria and chloroplasts are derived from once free-living prokaryotes taken inside another prokaryotic cell to create a eukaryote.
List the main events of the first half billion years in Earth’s history
Ga = Giga Annum/Billion years
Late Heavy Bombardment (4.1-3.8 Ga)
Oldest rocks (4.0 Ga), Acasta Gneiss, Canada
First liquid water on Earth (4.4 Ga) and oldest zircon crystal
Formation of the Moon (4.5 Ga)
Formation of the Earth (4.6 Ga)
Describe the atmospheric conditions and changes in the atmospheric conditions in the Hadean time period
Earliest atmosphere probably comprised hydrogen and helium
- Volatile gases were released during the formation on the
Moon in the Hadean - compounds such as methane and
ammonia and water vapour created reducing conditions (meaning oxidationn is prevented via absence of oxygen - By the late Hadean the atmosphere is thought to largely
consist of water vapour, nitrogen and carbon dioxide - The atmosphere only became oxygen-rich much later -
after it started being produced by bacteria via photosynthesis
What is the oldest zircon rock found?
What kind of rock is it and what is it evidence of?
The 4.4 Ga Jack Hills zircon is from a metamorphic rock
with a sedimentary protolith → oceans and at least some
continental crust existed at that time
Describe conditions in the Hadean and early Archean that would have made it difficult for life to develop?
The early oceans were hot, reducing and acidic, and
there was a lot of UV radiation due to the lack of ozone
- The Late Heavy Bombardment would have made it
difficult for life to evolve at the surface until afterwards - But it could have happened in deep marine hydrothermal
systems (Extremophiles)
Define Extremophiles
Organisms that live in environments that are inhospitable to most life.
- e.g. extremes of salinity,
pH, temperature etc. such
as hot springs and
hydrothermal vents
List the four ingredients for life
Water
Time
Energy
C - H - N - O - P - S
(Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur)
Describe the miller urey experiment
Abiogenesis = process by
which life arose from simple
organic compounds
- Life involves amino acids,
nucleic acids, lipids and
carbohydrates
Miller-Urey experiment (1952) - Synthesized amino acids from inorganic compounds
(water, methane, ammonia, hydrogen) - Electric spark to mimic lightning
What is the Panspermia hypothesis?
The theory that Life on Earth was ‘seeded’ from elsewhere in the
universe
Evidence that microbes
can survive in space
(years) from work by the
International Space Station and can survive the shock of being ejected into space
But the hypothesis merely shifts the problem as the life would have to find a way to start elsewhere.
Describe the Earliest evidence of life
Nuvvuagittuq Belt, Quebec,
Canada (4.28-3.77 Ga)
Tubes and filaments of hematite
* Seafloor hydrothermal vent
deposits
Isotopically light carbon ratio type from associated carbonate material, this suggest biological activity.
Jack Hills, Australia (4.1 Ga)
Zircon crystal with graphite
inclusions
* Isotopically light carbon ratio
* Biogenic processes fractionate the
isotopes of carbon to give a high
12C/13C ratio
Isua, Greenland (3.7 Ga)
Carbon isotope ratios and
stromatolites
* cm-scale layered structures made
from microbial communities
* Shallow marine environment
Apex Chert, Australia (3.5 Ga)
Cyanobacteria (2.7 Ga)
Great Oxidation Event (2.4-2.0 Ga)
Multicellular fossils (2.1 Ga)
Eukaryotic fossils (1.63 Ga)
