- Life Sciences
mass extinction event of 250 million years ago, in which about 90% of all species on Earth died out. It included a mass extinction of insects.
a social structure in which different classes are determined by heredity.
a chemical messenger produced and released by a cell or a gland in one part of the body of the...
wild animals from tropical forests that are captured or killed for food or traditional medicine...
epithelial tissue consisting of a single layer of cells.