The Biological Interactions

  • William W. Hay


The earliest life forms on Earth were chemoautotrophs, manipulating the chemistry of compounds to obtain energy. Photosynthesis and the ability to use the energy from the Sun evolved about 2 billion years ago. Over the ages living organisms have modified the surface of the planet. Life forms a thin veneer on the surface of the land, with plants consuming nutrients, water, and CO2 for photosynthesis to produce sugars and other compounds that they and animals ultimately use for energy. Two major categories of plants, C3 and C4 use different pathways for photosynthesis. C4 plants are thought to have evolved as an adaptation to the lower levels of atmospheric CO2 that characterize the icehouse climate. They conserve water and do not return as much of it to the atmosphere as C3 plants. Humans use many C4 plants for food and have spread them over many areas formerly covered by C3 plants. Growth of some plants is enhanced by higher levels of CO2 but others are inhibited. Whereas plants are the obvious life forms on land, animals are the large life forms in the sea. Most marine plants are microscopic. There is little free CO2 dissolved in the ocean so many marine algae obtain their CO2 through photosynthesis from the bicarbonate ion. Many of them get rid of excess CO2 by combining it with the calcium ion to make calcium carbonate. Small animals eat the microscopic plants and produce fecal pellets that sink into the deep ocean. As more CO2 enters the ocean, it becomes increasingly acidic, affecting the ability of many organisms to secrete carbonate.


Last Glacial Maximum Fecal Pellet Ocean Floor Planktonic Foraminifera Planktonic Foraminifer 
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Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  1. 1.University of Colorado at BoulderEstes ParkUSA

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