Photosynthesis vs. Chemosynthesis

The discovery of biological communities around deep-sea hot water vents is an exciting scientific event. Giant tube worms, large clams and shrimp with eyes but can detect light has opened up a new field of studies in marine science. The communities live nearly isolated from other marine communities and they have no contact with the sun which is the source of energy for most living things on earth.

Organisms on the Earthıs surface depend on plants to produce surface from sunlight ­ a process called photosynthesis. These communities are unique in that they depend on a different food-making process other than photosynthesis. Bacteria at the vents make sugar by a process call chemosynthesis. Rather than light they depend on the chemicals that are released into the water by the vents. Bacterial use chemical energy to produce organic food molecules. The Vent organisms are dependent on the bacteria just as animals at the surface depend on plants for food production.

Several types of organisms have been discovered in the vent communities. A spectacular tube worm Riftia pachyptila can grow up to 3 meters (10 feet) long and several variety of large clams that are up to 25 cm or 10 inches long. While Riftia sp is found near the Galapagos vents a smaller tube worm Ridgia sp has been discovered on the Juan De Fuca vents. These animals have no gut but get their food from chemosynthetic bacteria living in their tissues. The tube worms extract hydrogen sulfide form the vent water transferring it to an organ containing bacteria, here, the bacteria oxidize the hyrogen sulfide and turn it into food that can be used by the tube worm. The clams carry the bacteria in their gills and extract the Hydrogen sulfide as the water is circulated over their gills.

When the vents become inactive the energy source for generating food stops, and the community dies.

Formulas for food production (production of Organic Carbon) Photosynthesis:

H20 + C02 _ Light Chlorophyll = Ch20 + 02 Water Carbon Dioxide Organic carbon Oxygen

Chemosynthesis 02 + 4H2S + C02 _ CH20 + 4S +3H20 Oxygen Hydrogen sulfide Carbon dioxide Organic carbon Sulfur water

Activity ­ Using various colors of gumdrops and toothpicks, build the formula for both Chemosynthesis and photosynthesis. For example H molecules- orange gumdrops, carbon molecules- green and oxygen,-purple.

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