Early Planet: Early Life

Question 1

How long ago was the formation of th Earth

Answer 1

4.6 Billion years ago

Question 2

How did the solar system form

Answer 2

The solar system formed from an interstella cloud
This is a region of dust and hydrogen, which contracted under its own gravity
The Sun formed in a Hot and Dense centre of the cloud and the rest formed a disc called a solar nebula

Question 3

How did the Earth’s Moon form

Answer 3

In a giant impact event ca. 4.51 billion years ago
The Debris from this collision between Earth and Theia (a body the size of Mars) was used in the formation of the Moon

Question 4

What is the Late Heavy Bombardment (LBH) and when did it occur?

Answer 4

An estimated 17,000 large coments and asteroids bombarded Earth 3.8-3.9 billion years ago, making the Earth’s surface hundreds of degrees hotter than the highest temperature at which amino acids/nuclueodies can survive undamaged, hence destroying any possible previous life before that

Question 5

How does the start of life link to the Late Heavy Bombardment

Answer 5

Life as we know it, is though to have started 3.9 billion yearsa go after the Late Heavy Bombardment, as life before this would have been whipped out

Question 6

Give some examples about how life on Earth can survive in the most extreme places

Answer 6

Antartica (-94.7 degrees recorded in 2010)
Strain 121m - a microbe found on some hydrothermal (volcanic) vents in the Pacific) survived a ten-hour blast in an autoclava at 121 degrees
Hypersaline springs
Toxic waste dumps
Cracks deep in the Earth’s crust and saline brine in oil fields

Question 7

What is the main two difference between prokaryotic and eularyotic cells

Answer 7

Prokaryotes do not have a nucleus
Prokaryotes do not have membrane-bound organelles

Question 8

Which life form evolved first eukaryotic or prokaryotic

Answer 8

Prokaryotic life forms evolved first, and dominat the would unseen today and are fundamental to most biogeochemical cycles and processes
Eukaryotes evolved much later (1.7-2.0 bya) and eventually clubbed together to form multiceulluar organisms

Question 9

Name two ways of how life could have originated on Earth

Answer 9

Life must have arrived from elsewhere or was created on our planet, as early conditiion were such that nothing could have lived on it

Question 10

What organism is believe to be the earliest form of life and what evidence exists for this

Answer 10

Archeae (4.0-2.5 bya)
Archean rocks are found around the works, which are cherts. They are almost pure silica (glass) and yield apex fossils (form in aqueous environments)
They are believed to be formed through both seawater and hydrothermal fluids
Evidence of their age can come from the silicon isotopes in the cherts

Question 11

The cherts give evidence of life how many years ago

Answer 11

They give evidence of life as far back as 3.5 billion years ago

Question 12

When chemical evidence exists for the presence of early life

Answer 12

The Great Oxygenation event and Carbon isotope evidence shows that like was operting around 3.8-3.5 bya

Question 13

Going from unicellular to multicullular organisms, how long did this progression take to occur

Answer 13

There is a big gap in time between the existence of singular and multi-celled organisms

Question 14

How does the occurence of elements relate to the formation of Earth and life

Answer 14

Chemical elements made in the starts and spread through the universe when start explode - supernova
Elements become rarer as they get heavier. The study of both the Eath and life revolved largely around subsets of the first 30 elements

Question 15

> 90% of the non-living planet is made up of what 4 elements

Answer 15

Oxygen, Magnesium, Silicon and Iron

Question 16

What are Lithophile and Siderophile elements and how did they affect the formation of the Earths core

Answer 16

Lithophile - rock loving
Siderophile - iron loving and also iron
Lithophile and siderophile elements and elements that combine with oxygen are preferentially incorporated into rocks and metallic core when Earth formed, leading a relative deficiency at the surface (this includes mainly oxygen, magnesium, silicon and iron)

Question 17

What elements have little-to-no role in life and why?

Answer 17

The unreactive noble gases
They do not play a significant role in low-temperature chemical systems, such as life as they are fully intert
Hence, they are only found on their own and don’t play any part in life/biological systems

Question 18

How does the composition of the sun link to formation of life

Answer 18

For the lightest chemical elements (minus the lithophile/siderophile elements and noble gases) there is a strong correlation between the composition of the Sun and of all of life
Life statically has a great deal in common with the composition of the sun

Question 19

Carbon and Silicon are two different elements in the centre of the periodic table, that are fundamental to the composition of the planet and of life, what is the common feture between the two
And what does it show about elements involved in life

Answer 19

They both have a valence of +4
Elements involved in life need to be reactive

Question 20

Silicion is highly reactive with oxygen forming silicon dioxide (silica) and can form either glass or quartz
What is the difference between these two compounds

Answer 20

The multiple bonding capabilities of silicon gives us the main structural component of rocks - quartz, which is a more ordered crystalline structure than glass

Question 21

What is the difference between the silicon structures which form like silicion dioxide and organic compounds which form

Answer 21

Carbon can form 3D complexes in a similar way, but with carbon you get not brittle crystals but soft and pliable structures, and more reactive than silicon

Question 22

What are 5 advantages of Carbon over Silicon for life

Answer 22

1. Can bond to itself as well as other elements: C-C backbones
2. Can be and fold to make much more complex structures than silicon, which is rigid and inflexible
3. Can form molecules that are soild (bone/wood(, liquid (oil), and gas (carbon dioxide and methane), allow exchange of carbon between different phases of matter
4. Can form soluable and insoluable molecules, usful for transporting carbon or making carbon resistant to water damage
5. Can have mutiple eletrical states e.g +4 in carbon dioxide and 4- in methane

Question 23

Why is it then, that life is made up only of a small number of elements

Answer 23

Because of the elements that carbon bonds with and that are available at the Earth’s surgave in sufficient amounts

Question 24

What are 4 key biological organic molecules which are associated with all forms of life

Answer 24

Carbohydrates
Lipids
Amino acids
Nucleic acids

Question 25

What where pre-life condition like on Earth: specifically the oceans and atmosphere

Answer 25

Oceans: liquid water was present, the sea water salty and contains cations (sodium, magnesium and calcium) and anions (chloride) and around similar levels of today
Atmosphere: was moderately reducing (rather than oxygen-rich), the sun was 30% dimmer, and high levels of CO₂ kept the earth warm
Overall it was still contusive for life

Question 26

How is life on a basic level, thought to have come about

Answer 26

Organic biological molecules were made abiotically
Monomers for polymers and they where enclosed in a cellular container
And these cells replicated and evolved via natural selection

Question 27

What is a major stumbling block in the theory of abiotic synthesis of basic building blocks of life

Answer 27

They synthesised organic biological molecules would have been created in dilute concentrations and many had short lifespans, e.g., an amino acid made in the atmosphere by lightening is carrier to the ocean by rainwater, where it is unlikely to meet another potential life molecules
An environment in which life molecules are concentrated and hence comes together, is a hurdle
However there are many theories for this like primordial broth

Question 28

Many theories for getting the biological organic molecules together are highly distributed, for example: evaporative intertidal lagoons, concentration of molecules of mineral surfaces, clouds or subsurface cracks on rocks
Deep sea vents seems like quite a likely hypothesis: explain?

Answer 28

Strong chemical concentrations, favourable conditions for chemical reactions, abundant energy, metal catalysts, all could aid in the synthesis of diverse organic molecules now thought to be possible by the mixing of hot geothermal fluids within seawater
There is also no shortage of these geothermal vent across planet Earth