Credit: Lynn Betts, USDA Natural Resources Conservation Service
Topsoil is the upper, outermost layer of soil, usually the top 2 inches (5.1 cm) to 8 inches (20 cm). It has the highest concentration of organic matter and microorganisms and is where most of the Earth's biological soil activity occurs. Pictured: Terraces, conservation tillage, and conservation buffers save soil, control erosion and improve water quality on this Iowa farm. 1999.
Drawing of an American paddlefish (Polyodon spathula). Also called the Mississippi paddlefish or spoonbill, they live in slow-flowing waters of the Mississippi River drainage system and may grow to 7 feet (220 cm) and weigh up to 220 pounds (100 kg). They appear to have been extirpated from Lake Erie and its tributaries.
Some Hydrothermal ventssupport peculiar ecosystems, based on dissolved minerals. Hydrothermal vent communities are able to sustain such vast amounts of life because vent organisms depend on chemosyntheticbacteria for food. The water that comes out of the hydrothermal vent is rich in dissolved minerals and supports a large population of chemo-autotrophic bacteria.
Mold growth covering a decaying peach. The frames were taken approximately 12 hours apart over a period of six days. Molds are fungi that grow in the form of multicellular filaments called hyphae. Molds are considered to be microbes but microscopic fungi that grow as single cells are called yeasts.
Credit: Bruce Fritz, USDA Agricultural Research Service
Sunflowers were domesticated by humans, and are native to Central America. The evidence thus far is that it was first domesticated in Mesoamerica|, present day Mexico, by at least 2600 BC. It may have been domesticated a second time in the middle Mississippi Valley, or been introduced there from Mexico at an early date, as maize was. Sunflower leaves can be used as a cattle feed, while the stems contain a fiber which may be used in paper production.
An animation of the Earth's hypothesized Pangaea separation. Pangaea is hypothesized as a supercontinent that existed during the Paleozoic and Mesozoic eras about 250 million years ago, before the component continents were separated into their current configuration.
Termite mounds in Tanzania with varied heights of chimneys regulate gas exchange, temperature and other environmental parameters that are needed to sustain the internal physiology of the entire termite colony.
Schoolingbigeye trevally. In biology, any group of fish that stay together for social reasons are said to be shoaling and if the group is swimming in the same direction in a coordinated manner, they are said to be schooling.