Poaceae groups, using the C3 and C4 photosynthetic pathways for carbon fixation. The C4 grasses have a photosynthetic pathway, linked to specialized Kranz leaf anatomy, which allows for increased water use efficiency, rendering them better adapted to hot, arid environments and those lacking in carbon dioxide. The C3 grasses are referred to as "cool-season" grasses, while the C4 plants are considered "warm-season" grasses. The grass family is one of the most widely distributed and abundant groups of plants on Earth. Grasses are found on every continent, including Antarctica with the presence of Antarctic hair grass on the Antarctic Peninsula. Grasses are
Smallest organisms cetacean, which is also (as of 2006) the most endangered, is the vaquita. Male vaquitas grow to an average of around 135 cm (53 in); the females are slightly longer, averaging about 141 cm (55 in) in length. Duckweeds of the genus "Wolffia" are the world's smallest flowering plants. Fully grown, they measure only 300 µm by 600 µm and reach a mass of just 150 µg. Nanobes are thought by some scientists to be the smallest known organisms about one tenth the size of the smallest known bacteria. Nanobes, tiny filamental structures first found in some rocks and sediments,