Evolution and History of Life on Earth

Question 1

What did the big bang create?

Answer 1

Lightest elements

Question 2

What created the heavier elements?

Answer 2

Successive generations (to the big bang) of red giant stars, supernova, stellar collisions

Question 3

Why is it that out of >100 billion galaxies in the universe, only 10% are likely to have complex life?

Answer 3

The rest are probably sterilized by gamma ray bursts

Question 4

How much energy does the Sun provide for life on Earth?

Answer 4

Nearly all of it

Question 5

What is a strong indication of life on a planet?

Answer 5

If a planet orbiting a star has an atmosphere out of chemical equilibrium

Question 6

What is the Goldilocks Zone?

Answer 6

Where water can exist as a liquid

Question 7

Why is the earth’s atmosphere suitable for life?

Answer 7

Allows light penetration for photosynthesis but protects against excess UV light

Question 8

The Earth’s axial tilt is stabilised by what?

Answer 8

The moon - ecological, environmental stability

Question 9

The Moon gives Earth tides, what is the effect of this?

Answer 9

• increased biodiversity
• biological cues to time reproduction
• enhanced colonisation of life on land?

Question 10

What did collisions with Theia create?

Answer 10

The axis inclination to the plane of orbit => seasons

Cooling of earth => oceans formed

Question 11

Why is the axis inclination beneficial?

Answer 11

Saves EArth from overheating as happened to Venus

All of Earth gets warmed at sometime in the season

Question 12

What are the features of living organisms?

Answer 12

They reproduce
They transform energy
They grow
They respond to stimuli
They maintain stable internal environments - homeostasis

Question 13

What is Panspermia?

Answer 13

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

Question 14

What is Stage 1 of origins of life on Earth?

Answer 14

Monomers
New atmosphere formed
Earth cooled - oceans formed

Question 15

What is stage 2?

Answer 15

Polymers

More complex molecules formed such as proteins and nucleic acids

Question 16

What is stage 3?

Answer 16

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

Question 17

What is stage 4?

Answer 17

RNA
Development of genetic code to provide heritable mechanism
Rapid diversification of life forms driven by natural selection

Question 18

How old if the oldest fossil?

Answer 18

~3.5 Gyrs, Stomatolites

Question 19

When is the earliest prokaryote?

Answer 19

~3.9 Gyrs ago

Question 20

How long were prokaryotes Earth’s sole inhabitants?

Answer 20

~1.5 Gyrs

It was they that initially changed Earth’s atmosphere, they were first to colonise land

Question 21

When was the earliest eukaryote?

Answer 21

~2.1 Gyrs (possibly as early as 2.7 Gyrs) - Endosymbiosis (mitochondria, chloroplasts etc)

Question 22

What are the three domains of life?

Answer 22

Bacteria
Archaea
Eukaryota

Question 23

How common is extinction?

Answer 23

99.9% of species are estimated to be extinct
Extinction is continuous
Most species last average ~ 2Myrs

Question 24

How many mass extinctions has there been?

Answer 24

5 so far

Question 25

What is the effect of a mass extinction?

Answer 25

Mass extinctions, whether caused by terrestrial or extra-terrestrial events, or combinations of them, allow major changes in the dominant life forms
The rise of the dinosaaurs
then
The rise of the mammals