Evolution and History of Life on Earth Flashcards
(25 cards)
What did the big bang create?
Lightest elements
What created the heavier elements?
Successive generations (to the big bang) of red giant stars, supernova, stellar collisions
Why is it that out of >100 billion galaxies in the universe, only 10% are likely to have complex life?
The rest are probably sterilized by gamma ray bursts
How much energy does the Sun provide for life on Earth?
Nearly all of it
What is a strong indication of life on a planet?
If a planet orbiting a star has an atmosphere out of chemical equilibrium
What is the Goldilocks Zone?
Where water can exist as a liquid
Why is the earth’s atmosphere suitable for life?
Allows light penetration for photosynthesis but protects against excess UV light
The Earth’s axial tilt is stabilised by what?
The moon - ecological, environmental stability
The Moon gives Earth tides, what is the effect of this?
- increased biodiversity
- biological cues to time reproduction
- enhanced colonisation of life on land?
What did collisions with Theia create?
The axis inclination to the plane of orbit => seasons
Cooling of earth => oceans formed
Why is the axis inclination beneficial?
Saves EArth from overheating as happened to Venus
All of Earth gets warmed at sometime in the season
What are the features of living organisms?
They reproduce They transform energy They grow They respond to stimuli They maintain stable internal environments - homeostasis
What is Panspermia?
The hypothesis that life exists throughout the Universe, distributed by space dust, meteroids, asteroids, comets, planetoids, and also by spacecraft carrying unintended contamination by microorganisms
What is Stage 1 of origins of life on Earth?
Monomers
New atmosphere formed
Earth cooled - oceans formed
What is stage 2?
Polymers
More complex molecules formed such as proteins and nucleic acids
What is stage 3?
Protobionts
Protobionts are collections of organic molecules enclosed by a membrane
Certain lipids can self-organise to form a spherical membrane around organic molecules
Non-living but can exibit some features of life ie polarised membranes, simple metabolism
What is stage 4?
RNA
Development of genetic code to provide heritable mechanism
Rapid diversification of life forms driven by natural selection
How old if the oldest fossil?
~3.5 Gyrs, Stomatolites
When is the earliest prokaryote?
~3.9 Gyrs ago
How long were prokaryotes Earth’s sole inhabitants?
~1.5 Gyrs
It was they that initially changed Earth’s atmosphere, they were first to colonise land
When was the earliest eukaryote?
~2.1 Gyrs (possibly as early as 2.7 Gyrs) - Endosymbiosis (mitochondria, chloroplasts etc)
What are the three domains of life?
Bacteria
Archaea
Eukaryota
How common is extinction?
99.9% of species are estimated to be extinct
Extinction is continuous
Most species last average ~ 2Myrs
How many mass extinctions has there been?
5 so far
