U.S. Greenhouse Gas Emissions. In the United States, greenhouse gas emissions caused by human activities increased by 7 percent from 1990 to 2014. Since 2005, however, total U.S. greenhouse gas emissions have decreased by 7 percent. Carbon dioxide accounts for most of the nationâs emissions and most of the increase since 1990. Electricity generation is the largest source of greenhouse gas emissions in the United States, followed by transportation.
The phylum Arthropoda (jointed foot) has the largest number of species. In fact, about 85 percent of known species are arthropods, and insects alone make up about 75 percent of known species. Other arthropods include the centipedes and millipedes; the arachnids (spiders, scorpions, ticks, mites); and the crustaceans (barnacles, crabs, crayfish, lobsters, shrimp, water fleas). Obviously,
The nine largest phyla contain the majority of species. One phyla, the arthropods, which includes insects and spiders, constitutes about 75 percent of all known animal species. More than 900,000 arthropods have been described, and according to some estimates there may be more than five million more.