Resource: Deep Sea Vents and Life's Origins

Bacteria found deep in the ocean in the volcanic regions of mid-ocean ridges suggest a possible scenario for the beginning of life on earth.

Ocean water seeps into cracks created by sea-floor spreading at the mid-ocean ridges and is heated by magma from inside the earth. Water in these hydrothermal vents reaches temperatures of 375 degrees C and higher and is rich in dissolved minerals. The hot water rises from the vents in geysers and meets cold ocean water, causing minerals to precipitate out of solution as the water cools. In some places compounds of iron and sulfides form "chimneys" on top of the vents. Such an extreme environment seemed unlikely to support life given the conditions of temperature, pressure, and absence of light for photosynthesis.

In 1977, Alvin, one of the first manned submersible vessels that could withstand extreme deep-sea pressures, made dives to the ocean floor during which its crew made a surprising discovery -- an ecosystem surrounding the hydrothermal vents of the mid-ocean ridges.

Bacteria called chemoautotrophs are the producers in the food chain, oxidizing sulfides to provide energy for synthesizing organic compounds. Species of tube worms, clams, mussels, and other organisms are the consumers. These communities cannot rely directly on photosynthesis, because sunlight cannot penetrate such depths. However, the oxygen dissolved in ocean water is produced by photosynthesis near the surface of the ocean.

The appearance of bacteria in these extremely hot, high-pressure, and dark environments has caused scientists to speculate that hydrothermal vents or places like them might be sites of the earliest appearance of life on earth -- fueled by water, energy from chemical reactions, and a rich supply of resources.

How does all the life you saw in the video survive without sunlight?

What are deep-sea vents? How are they formed?

How do deep-sea vent organisms survive in such extreme conditions?

Choose an organism that intrigues you and describe it.

What is the ultimate food source in the vent community? or How do these organisms get food?

Describe the Mid-Atlantic Ridge.