ESS W2 L1 pt 2 - cycles of energy

cycle of energy in the biosphere

Definition of the biosphere:

• Vladimir Vernadsky (1863-1945) :

•    “Activated by radiation, the matter of the biosphere collects and redistributes solar energy, and converts it ultimately into free energy capable of doing work on Earth (…).” Biosfera, 1926

Solar energy:

• Earth receives energy from the sun

•   But the same amount of energy we receive from the sun is released back into space (mainly as heat energy)

• First law of thermodynamics

  • Energy isn’t destroyed its transformed

•    What happens to that energy?

law of entropy:

•    2^nd law of thermodynamics

•   A common way to describe entropy is an increase in disorder – things become more mixed or random, over time

•    It could be described as the spreading of energy over time

•    Entropy is why hot things cool down and cold things warm up

• Or why gas expands to fill a container

• Entropy is constantly increasing over time

If entropy (disorder) is constantly increasing, how is there life on earth?

• If earth was a closed system, then eventually the spread of energy (entropy) would mean that the temperature of earth would be the same, and life would die out, everything would decay.

• But earth is not a closed system as we have the sun

Entropy:

• The sun gives us a constant stream of low entropy energy

•   Plants use this energy to grow and release heat energy (high entropy)

• Animals eat these plants, releasing more heat energy

•   At each step, energy becomes more spread out – converting to high entropy energy

• We receive high energy (low entropy) protons from the sun

• The earth releases back the same amount of energy but in low energy protons (high entropy)

entropy - dissipating energy

• Life is highly efficient at dissipating energy, converting it from low to high entropy

•   Energy transfer: As energy moves through the food chain, some of it is lost as heat (thermal), which increases entropy

•   Ecosystems are driven by the flow of energy and the increase in entropy

• We are facilitating entropy, we are ‘doing the work’

But life can go against the law of entropy:

• However, life itself is highly organised, and can maintain a low entropy (ordered) structure

• For example, during photosynthesis plants consume light from the sun and convert it into high entropy thermal energy, but at the same time decreases its internal entropy by producing sugars and carbohydrates (which are low entropy).

• As more heat than sugars are produced, there is an overall increase in entropy, maintain the Second Law of Thermodynamics.

atp - add cycle powering life

• atp - adenosine triphosphate

• adp - adenosine diphosphate

• two key parts to photosynthesis - light and dark reactions

• this constant cycle of atp into ads powers this life

atp - add cycle powering life - light reactions

• Sunlight captured by chlorophyll in chloroplast s- absorbs light energy into chemical energy – stored in energy molecules – ATP and NADPH

•   Water is being split into hydrogen and oxygen – oxygen produced through hydrolysis

• ATP – three phosphate groups – bonds of this group which contain energy

• ATP changed into ADP

• This drives the dark reaction

atp - add cycle powering life - dark reactions

•   Co2 drawn down into biomass through enzyme rubisco – atmospheric carbon drawn into biomass through sugars

• Rubisco is most abundant protein on earth

•    Most organic carbon transferred from atmo in this way

Photosynthesis from space:

• Seeing photosynthesis from space

• White light – transformed into fluorescence

autotrophs

• an organism that can produce its own food using light, water, carbon dioxide, or other chemicals – the foundation

• The carbon compounds made by plants are food for other organisms.

• e.g. plants, algae, many bacteria

heterotrophs

• an organism that eats other plants or animals for energy and nutrients – consumers

• e.g. animals, fungi, many bacteria

Heterotrophic respiration: the krebs cycle

• Heterotrophs use carbon compounds in respiration

• Take carbs. Sugars etc – use krebs cycle to break them down

Flow of energy in the biosphere: