Lecture 5: Gaia Hypothesis

Question 1

What approach did James Lovelock take to determining whether life on other planets could exist? What aspect of the planets did he devote particular attention toward?

Answer 1

He looked at the different planets alongside our knowledge of how life affects our planet already. One particular area he looked at was the differing atmospheric compositions

Question 2

Why were Lovelock’s efforts to determine whether life existed on other planets unpopular amongst his peers?

Answer 2

Because it undermined the credibility of their efforts to determine whether life existed on another planets

Question 3

What was the conclusion of Lovelock’s work looking at whether life existed on other planets, notably Mars?

Answer 3

That it demonstrated no current or previous indications of life

Question 4

What do low-entropy/living things do?

Answer 4

They produce high-energy waste products

Question 5

What do the high-energy waste products match with?

Answer 5

The high-energy waste products are of high disorder which matches with the growing disorder present in the universe

Question 6

What did Schrodinger state in 1944?

Answer 6

life will always change its surroundings by releasing unusual volatiles and other gases that normally react with each other to vanish, but instead they are maintained causing an unusual mixture in the atmosphere.

Question 7

What is the idea of disequilibrium?

Answer 7

When things coexist which are highly reactive with each other remain abundant in independent forms

Question 8

Is the earth in disequilibrium and what is this evident from?

Answer 8

Yes - extreme disequilibrium - evident from the unusual mixture of gases that are highly reactive with each other such as Methane and Oxygen and would normally not be separate

Question 9

Why is the earth’s atmospheric composition in extreme disequilibrium?

Answer 9

Because life generates large fluxes of gases in order to survive which then alters the atmosphere

Question 10

What did Lovelock hypothesis from looking at the atmospheric composition over time?

Answer 10

That because the composition has been preserved and stable over time, life must be regulating the atmosphere not just inputting new gases

Question 11

Who produced the knowledge about the Faint Young Sun Puzzle?

Answer 11

Carl Sagan

Question 12

What theory did Lovelock develop working with Carl Sagan regarding the faint young sun puzzle?

Answer 12

that is the sun was brighter by 30% before why was it not frozen over? It must have been because the greenhouse gas layer was being altered relative to the sun’s brightness. Vegetation must have been responsible for these changes and therefore alters the climate

Question 13

What was the Gaia hypothesis?

Answer 13

The theory co-produced by Lovelock and Marguilis which outlined how they believed life was altering numerous aspects of earth

Question 14

Where did the name “Gaia” come from and what controversy did it have around it?

Answer 14

It was the name of a Greek goddess and it received controversy because it combined quasi and religious ideas

Question 15

What were some of the topics the Gaia hypothesis wanted to explore?

Answer 15

1. Atmosphere disequilibrium, yet stable components
2. Why are gases perfectly suitable? e.g. oxygen
3. Stable climate despite faint young sun puzzle
4. Acidity and redox potential of earth’s surface anomalous yet tolerable

Question 16

What was the mechanism found in the sulphur cycle that enabled it to recycle?

Answer 16

Dimethyl Sulphide - it resupplied sulphur back to the atmosphere and allowed for sulphur to continue precipitating on the land

Question 17

What was the mechanism that allowed iodine to be replenished in to the ocean?

Answer 17

Methyl Iodide found in the marine biology

Question 18

What problems was Lovelock experiencing with getting his Gaia hypothesis to the public? How did he overcome it?

Answer 18

No journal would publish his theory. He would publish a book

Question 19

Who were two notable peers of Lovelock that criticised his theory? What did they critique?

Answer 19

Dawkins and Doolitle - how could unconscious bacteria consciously determine their environment

Question 20

What was the name of Lovelock’s response to criticism of his work?

Answer 20

Daisyworld

Question 21

What was “Daisyworld”?

Answer 21

A model that showed how plants (daises as an example) could automatically alter and regulate their envrionment

Question 22

What were the two types of plant that he included in the Daisyworld model?

Answer 22

Black Daises - absorb more sunlight which warms their surroundings
White daises - absorb less sunlight

Question 23

What will happen to black daises if luminosity and therefore temperature reaches a suitable level for growth? What subsequent effect will happen?

Answer 23

They will start to grow - meaning there is more black present which increases temperature more (feedback)

Question 24

What will happen to black daises when they become too many and temperature reaches too much?

Answer 24

If there are too many daises then the temperature will be too hot so they will start to decline, which dampens the feedback and eventually will vanish as all black daises are gone

Question 25

What will happen to white daises if luminosity and therefore temperature reach a suitable level for growth? What subsequent effect will happen?

Answer 25

They will start to increase but because they are white there is a negative feedback i.e. the more the temperature increases, the slower the daises start to grow.

Question 26

What will happen to white daises when the luminosity increases too much?

Answer 26

It will be too hot for the daises to continue dampening the effect by cooling their environment. This will reduce albedo and therefore temperatures will increase even more. Once all daises have gone the temperature relationship will normalise.

Question 27

Which daises will dominate at the lower level and the upper levels of luminosity/temperature? Think about the reason

Answer 27

Lower - black daises (They absorb more heat so can tolerate the cooler temperatures)
Upper - White (They reflect the heat so can tolerate higher temperatures)

Question 28

What is the transition between the two daises dominance characterised by?

Answer 28

A slight negative temperature line i.e. it decreases from the transition between black and white daisy dominance

Question 29

What is the daisyworld model a demonstration of?

Answer 29

Planetary-scale self-regulation can happen automatically

Question 30

What was the second part of the Gaia hypothesis looking at?

Answer 30

Ocean salinity

Question 31

What is the ocean salinity level suitable for life today and what would be fatal?

Answer 31

Today = 3.4%
Fatal = 6%

Question 32

What did Lovelock propose as the regulating mechanism for ocean salinity that then came to be wrong?

Answer 32

Coral reefs would create lagoons behind them with salt landforms being created to separate it from the ocean

Question 33

What are the known outputs/regulators of ocean salinity today?

Answer 33

Mid-ocean ridges: these can provide and take material from the ocean to the crust. Assisted by black-smokers.
Subduction: ancient salt sediments taken down and stored below the crust

Question 34

What are black smokers and how can they help regulate ocean salinity?

Answer 34

They release hot water that depending on its balance with ocean salt can either enter or remain in sea. The salty elements are also assisted by the high reactivity in these areas so then form rocks that cannot interact

Question 35

What did Alfred Redfield realise in the 1930s and 1950s?

Answer 35

There was a particular balance of nitrogen and phosphorus in the oceans that matched the requirements of organisms.

Question 36

What was his explanation for the similarity between organism requirements and ocean content of these ocean nutrients?

Answer 36

Life was responsible for setting the ratio in the ocean. Certain organisms can fix nitrogen in to its bioavailable forms so their activity adapts to and regulates the changing level of nitrogen so that it can be used for the organisms

Question 37

What is the name of the ratio between plant concentrations of phosphorus and nitrogen and the ocean concentrations?

Answer 37

Redfield ratio

Question 38

Did Redfield’s ideas predate Lovelock’s and what does this suggest?

Answer 38

They predated his ideas which suggested that he was way ahead of his time