Week 5 Flashcards
What makes earth habitable?
Goldilock’s distance
Carbon abundance
Insulating atmosphere
Liquid water
Magnetic field
When was the formation of earth?
4.57bn years ago
What is the period of 4.57bn years ago called?
The Hadean
What are the events of the hadean period?
Cooling and differentiation of the earths layers
Stabilisation of the atmosphere
Great impact
How old are the oldest rock records?
Only 4.03bn years
What caused the differentiation of the earth’s core?
Bombardment of asteroids delivered more material
Metal will separate from the silica
Metal will sink towards the centre of the planet forming a core
How did earth maintain light elements?
Comets, and early proto planets with carbon- rich cores delivered very light volatile elements
How did the moon form?
The collision of Theia, 4.53bn years ago added material to the earths core and sent debris into orbit
The orbit coalesced and formed the moon
What was the Hadean atmosphere like?
Toxic dense and smoggy, volcanic activity released volatile gases into the atmosphere
CO2 and methane created insolation
When and how were our oceans formed?
4.4bn years ago the earth cooled enough to support liquid water.
Water vapour that had accumulated in the atmosphere condensed and rained down creating acidic pools of water.
When was the Archean period?
4.0-2.5bn years ago
What were the events of the Archean period?
Late heavy bombardment
Plate tectonic formation
Earth’s magnetic field
Atmospheric development
How did the magnetic field form?
Convection currents churns the liquid outer core and generates electric currents which powers the earth’s magnetic field
What was the late heavy bombardment?
The continual attack of asteroids causing damage to the young crust and vaporizing the ocean
What is the evidence for a permanent ocean?
The formation of metamorphosed sedimentary rocks
What was the atmosphere like in the archean period?
Most H2O would’ve been lost when the ocean formed.
The ocean also becomes a sink for CO2 removing it from the atmosphere
Remaining atmosphere would be high in nitrogen
What defines a prokaryote?
No membrane bound organelles
DNA is free floating
70S ribosomes
Asexual reproduction
Unicellularity, binary fission
When was the oldest eukaryote fossil formed?
Grypania 2.1bn years ago
Development of life timeline
Simple polymers
Prokaryotic cells=3bn years
Photosynthetic cells
Cyanobacteria
Smaller cells within larger cells
First eukaryotic cells =2bn years
What are stromatolites?
Microbial mats built from bound falling sediments
What is the oldest stromatolite?
3.4bn years
What was the first evidence of sexual reproduction?
Bangiomorphia pubescens- red algae 1.05bn years ago
How can we look for signs of life?
Body fossils- the physical remains of an organism
Trace fossils- Evidence of activity such as footprints
Chemical footprints- Such as pigments, dna or sterols
How many ice ages were there?
- Sturtian glaciation
- Marinoan glaciation
- Gaskiers glaciation
What caused these snowball events and how did they subside?
Snowballing is caused by a runaway albedo effect from the expansion of ice sheets.
Desnowballing is caused by volcanic activity and the release of greenhouse gases
What was the impact of snowball events on evolution
Limited habitat space and extreme conditions selected for larger mobile complex organisms
What is the oldest animal?
Sponges- 600million years ago
What are the characteristics of the edicarian biota?
Soft bodies (no shells etc)
Frondose- look like sea pens
Erniettamorphs- inflated tubes on midlines
Dickinsonia rex- flat bilaterian
