They say life began in the oceans.  We know that the lithosphere is cracked, adding new land, subducting land over time.  But much of the lithosphere is covered with water – and here life began.  Initially it had to begin on either rock or sand.  The sand would have been produced by the weathering and erosion of rock.  Obviously, this would all have had to occur over a long period of time.  But the first forms of life would have to be able to find food and nutrition from a barren seafloor with little to offer.  This would take a special community of creatures – ones we call the pioneer community.

Key members of these communities would have been the producers’ ones who produce food.  What we know now is that producers absorb carbon dioxide and water and – using the sun as a source of energy – convert this into carbohydrates and oxygen.  We have since learned that there are ancient forms of bacteria that can do this with hydrogen sulfide and other compounds.  However, it started – it began.  One problem with this model is that much of the world’s oceans are too deep for sunlight to reach.  Thus, living organisms would need to be close to shore.  Today we know two things.  One, the ocean’s surface is covered with microscopic plant-like creatures (phytoplankton) who can float and reach the sunlight. Two, some of the ancient chemosynthetic bacteria (those that do not need the sun and can use other compounds to produce carbohydrates) live on the ocean floor.

Producers are followed by consumers, creatures who cannot make their own food and must feed on either the producers or on other consumers.  There are plankton feeding animals – oysters, sponges, corals, and zooplankton.  There are larger creatures that feed on larger plankton – manta rays, menhaden, and whales.  There are consumers who feed on the first order of consumers – stingrays, parrotfish, and pinfish.  And there are the top predators – orcas, sharks, and tuna.  The ocean is a giant food web of creatures feeding on creatures.  All creatures evolve defenses to avoid predation.  Predators evolve answers to these defenses.  Some species survive for long periods of time like the horseshoe crabs and nautilus.  Others cannot compete and go extinct.

As we mentioned in Part 1 of this series – the hydrosphere is in motion.  Different temperatures, pressure, and the rotation of the planet move water all over.  These currents bring food and nutrients, remove waste, and help disperse species across the seas.  Life spreads to other locations.  Some conditions are good – and life thrives.  Others not so much – and only specialists can make it.  The biodiversity of our oceans is an amazing.  Coral reefs, mangrove forests, and seagrass beds are home to thousands of species all interacting with each other in some way.  The polar regions are harsh – but many species have evolved to live here, and the diversity is surprising higher than most think.  The bottom of the sea is basically unknown.  It has been said we know more about the surface of the moon than we do at the bottom of our ocean.  But we know there is a whole world going on down there.  We believe the basic principles of life function there as they do at the surface – but maybe not!

Fossil records suggest life here began almost one billion years ago.  The fossils they find are of creatures similar and different from those inhabiting our ocean currently.  As we stated that the physical planet is under constant change – life is as well.  It is a system that has been working well for a very long time.  Over the last few centuries humans have studied the physical and living oceans to better understand how these systems function.  They have been functioning well for a very long time.  And though life began at sea – there was dry land to exploit – for those who could make the trip.  That will be next.

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