The seas are large masses of salt water determined by archipelagos, large islands or peninsulas or by relatively close land.

 

 

 

The oceans, much larger, separate the continents and reach a much greater depth.

 

 

  

 

The continents are extended under the water by a continental platform of about 200meters deep!

 

  

 

This platform ends by a steep drop, the continental slope, which reaches the great depths towards 3000 m depth!

 

 

 

Although the oceans and seas communicate with each other, their salinity, density and temperature are different.

 

  

Thus the tropical waters are more saltythan the waters where the great rivers flow, and the cold seas because of the greater evaporation, or because the salts dissolvesbetter in hot water.

 

 

The highest salinity is found in the RedSea (44 g / L on average and up to 300 g / L locally), the lowest in the Baltic Sea(2 g / L) with an average salinity of 35 g/ L!

 

 

There are two large zones of relatively homogeneous depth and characteristics:

The euphotic zone and the aphotic zone!

 

 

 

Concerning the euphotic zone:

The term euphotic comes from the Greek "eu" (good) and photos (light).

 

 

 

 

It is a shallow area, where light still arrives, where many plants live and where oxygenation is maximum.

 

 

 

It is divided into a hemi-peleagic zone(0 to 50 meters deep) and in a mesopelagic zone (-50 to -200 m) that only the ultraviolet reaches and the only plants are red and brown algae!

 

 

The aphotic zone encompasses everything else! 

The darkness is total, the infra-pelagic zone(-200 to -600m) is distinguished, 

 

 

 

enriched in nutrients by the proximity of the coasts and the euphotic zone populated by numerous animal species;

 

 

The bathypelagic zone(-600 to -2500m), which comprises most of the waters and where only large carnivores and species adapted to the depths live;

 

 

 

And finally the abyssopelagic zone(-2500m and more ), almost deserted!

The pressure increases with the depth of about 1000 hectoPascal every 10 meters.

 

 

 At 200m below sea level, each square centimeter must support 1,023kg.

The temperature decreases irregularly and differently according to latitude.

 

 

At the equator it is on average 30 degrees C to the surface, 15 degrees C to -250 m, 8degrees to -500 m, 5 degrees C to -1000 m and stabilizes between 5 and 0 degrees C to -4000 m!

 

  

 

Thus the temperature commonly found on the surface at the poles is found only 4000 m deep at the equator!

 

  

 

In addition, more than 90% of the world's water is in the oceans, which have an average depth of 3800m!

 

 

 

 

 

Finally, the inland seas and lakes are important reservoirs of more or less sweet water.

Depending on their origin, there are:

 

 

 

The volcanic(circular)lakes,

The glaciers(of elongated and irregular shape) resulting from the melting of old glaciers,

   

Tectonics(irregularly shaped) formed by movements of the earth's crust, such as the Dead Sea,

The coastal(formed of brackish water),

The Karstics(occupying the clay depressions),

 

 

 Residual lakes, which are remnants of ancient seas or gulfs, such as the CaspianSea,

The alluvial originated by the massive fall of rain,

 

 

 

 

And finally, the dams, whether natural or artificial, that the engineer, or the architect was a beaver or a man! 

The three main satellites of Jupiter also have notable hydrospheres!

 

 

 

 

 

Europe, whose surface is covered with ice, presented a subglacial ocean a hundred kilometers deep under the entire ice watercrust 

 

 

  

Ganymede would probably have a hydrosphere analogous to that of Europe with the presence of an ocean caught between two layers of ice.

 

 

 

Callisto could also have an ocean under its surface!

 

  

 

 

 

Finally, Gliese 581 c, which is the most similar known exoplanet to the Earth, gravitating in the habitable area of Gliese 581,

 

 

 

has an average temperature which could be between 0 degree and 40 degree celcius, which would allow the presence of Water in the liquid state on its surface!

The biosphere is the global, self-sustaining, or autocatalytic ecological system.

 

 It integrates all living beings and the relationships they create between themselves and with the compartmentsof the lithosphere(rocks),

 

 

The hydrosphere(water), and the atmosphere (air), in a metabolism that continually transforms the surface of the Earth by recycling or storing the elementsand creating complexity.

 

The concept of the biosphere intersted, in a religious context, Teilhard de Chardin, a French Jesuit priest, a researcher, a paleontologist, a philosopher, and a theologian.

  

 

He also used the term "noosphere", constituted by the human phenomenon, above the biosphere.

 

  

 

Beyond the beliefs, understanding the concepts of modern scientific ecology has popularized the appellation

 

 

 

and developed the perception of the environment of planetEarth, host of the biosphere!

 

 

 

Moreover, the deep biosphere is the deepest and underwater part of the biosphere and probably the least known!

 

  

 

It consists essentially of bacteria, arches(archeobacteria), and marine virusesadapted to life in extreme conditions. 

 

 

The exchanges between the different envelopes of the Earth are multiple, complex and permanent.

 

 

Life on our planet is closely linked to the atmosphere, as a reservoir of chemical elements like carbon, hydrogen, oxygen, nitrogen, sulfur...

 

The atmosphere is a privileged stage of the circulation of the abiotic chemical elements used for the edification of living beings!

 

 

 

Indeed, living organisms need about fortyelements to synthesize their own matter 

It's about:

 

  

 

Carbon( C ), nitrogen( N ), hydrogen( H ), oxygen(O ), sulfur and phosphorus!

 

 

These are the most important because they constitute the essential part of livingmatter; They alone account for about 95 % of the atomic make-up of living beings.

 

   

Macroelements such as potassium, calcium, magnesium, sodium...

 

   

 

They are necessary in "relative" large quantity.

Trace elements like zinc, copper... needed in very small quantities.

 

 

These elements pass alternately from livingmatter to mineral matter through cycles of varying length and complexity: biogeochemical cycles.

 

 

A given element can thus pass through the biosphere, along the food chains, to find itself in the atmosphere ...

 

 

 

Then in the oceans, be stored for very long periods in sediments before being released and reused again by living organisms!

 

 

It must be emphasized, however, that the biogeochemical cycles of these various elements do not necessarily pass through the atmosphere such as phosphorus, for example.

 

  

In addition, we must mention the essential role of water( H2O ) whose cycle intervenes in almost all the mechanisms intervening on Earth: climate, erosion, life...

 

  

 

Oxygen and carbon constitute 83.5 % of the atoms of the human body.

 

 

  

Organized in molecules with hydrogen and nitrogen, they constitute the major part of the organic matter characteristic of livingbeings.

 

   

The carbon atom has very special characteristics:

 

 

 

On the one hand, it behaves like a neutralatom capable of combining with electropositive atoms and electronegativeatoms;

 

 

 On the other hand, each carbon atom is capable of forming four bonds with other atoms and about one million different compounds of carbon are presently listed.

 

 

In addition, carbon and oxygen play a predominant role in the energy mechanisms essential to living beings.

 

 

 

 

 From an energy point of view, there are two types of living things:

 

 

Autotrophs, which are organisms capable of building their own material from the various mineral elements of their environment.

 

  

For example, during photosynthesis, chlorophyll plants are able to form their organic matter from carbon dioxide(CO2), water and mineral salts, using light energy.

 

 

Dioxygen released into the atmosphere can be considered a waste of photosynthesis.

 

 

Heterotrophs, which are organisms that elaborate their organic matter from moleculesmade by other living or dead beings.

 

 

 

They use them as raw materials and as a source of energy for two different mechanisms:

 

  

 Fermentation in an anaerobic(dioxygen free) environment in which organic molecules are degraded incompletely and with release of CO2,

 

 

such as the transformation of glucose into ethanol during the alcoholic fermentation carried out by certain bacteria.

 

 

 Aerobic respiration(with dioxygen) in which all energy molecules are degraded to CO2 and H2O that are released to the atmosphere,

 

such as during the transformation of glucose during animal or plant respiration.

The yield of respiration is much higher than that of fermentation!

 

 

Thus, the degradation of one mole of glucose released has nearly 45 times more energy during breathing than during fermentation.

 

 

 

So breathe, rather than rot! 

 Atmospheric oxygen, although it may result from the dissociation of water, is essentially of phosynthetic origin.

 

 As a result, the oxygen cycle is often associated with that of the carbon to which it is antiparallel in its main path: combustion and respiration deplete the oxygen that is reconstituted by photosynthesis.

 

 

In fact, the oxygen cycle, because of its ability to participate in multiple chemical combinations is very complex.

 

  

For example, the formation of ozone(3O2<-> 2O3 ), or the oxidation of minerals such as iron ( 4FeO + O2 -> 2FeO3)...

 

 

 

The oxygen cycle is a biogeochemical cycle that explains the transformations of oxygen in the terrestrial biosphere.

 

  

 

It is inseparable from the carbon cycle,because carbon dioxide is used during photosynthesis.

 

  

 

The latter produces dioxygen, which, through respiration, burns the carbon components produced by photosynthesis to give back carbon dioxide.

 

 

Photosynthesis and respiration are at the origin of the production and the equilibrium of atmospheric gases.

 

 

 

The two mechanisms CO2 + H2O -> sugars + dioxygen and vice versa, condition the circulation of carbon and oxygen.

 

 

This cycle explains the phenomenon of the appearance of ozone.

The use of cars emits nitrogen dioxide(NO2).

 

  

 

This, by decomposition and then recomposition with the ambient dioxygen(O2), forms ozone(O3).

  

  

 

However, this ozone is detrimental to health and is even considered a pollutant.

 

 

 

However, in the upper atmosphere, ozone forms a layer which is essential, indeed it acts as a filter with respect to the UV emitted by the sun.

 

Thus, and in a simplified manner, we have:

NO2 -> NO + O

and

O + O2 → O3.

The love of formulas....