Nearly one billion dollars a year are spent on clearing sediment from streams and lakes in the united states. which is the most common source of this sediment? a. productive farmland that is over-irrigated b. waste dumped by mining industries into the waterways c. hilly areas where protective vegetation has been removed

Afisherman is dragging his boat from the shore out into the ocean. match the following lists of areas he will move over in the correct order. continental rise continental slope continental shelf [tex]1.[/tex] [tex]2.[/tex] [tex]3.[/tex]

African penguins, which inhabit the coasts of southern africa, were classified as an endangered species in 2010. two significant threats to their survival are ecosystem damage from oil spills and overfishing by humans. overfishing depletes the food supply of african penguins. the best method to reduce the threat of overfishing would be to . the risk of oil spills could be reduced by increasing the use of , which should oil consumption. if an oil spill does occur, could be used to remove the oil so the ecosystem may more quickly recover.

Hydrilla (hydrilla verticillata) is an invasive aquatic plant and one of the most serious aquatic pests in florida. hydrilla has already been introduced to hundreds of bodies of water throughout florida, hydrilla is difficult to control because it grows rapidly and survives in many different water depths and conditions. hydrilla • describe how hydrilla affects native plant and animal species. include both a biotic and an abiotic limiting factor. • suggest one biotic and one abiotic recommendation that could slow the spread of hydrilla