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A common psychiatric disorder (especially in children) characterized by attentional difficulties, impulsivity, and hyperactivity. Attention deficit hyperactivity disorder (ADHD) is a mental disorder marked by an individual's inability to pay…

The quantitative assessment of individual hearing, both normal and defective. In typical tests, pure tones are presented through headphones, though some tests use speech instead of tones. In bone conduction tests, tones are presented through a…

Any member of an adaptively diverse group of extinct hominin species that inhabited Africa between approximately 4.2 million years ago (MYA) and 1.2 MYA. The term australopith is used in preference to the term australopithecine, which is sometimes…

A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism have difficulties with social communication and interaction. They also can have unusual behaviors, such as…

A class of nonflagellate unicellular algae, commonly called diatoms, with boxlike silicified walls. Diatoms range in maximum dimension from 4 micrometers to more than 1 millimeter. The diatom wall or frustule (Fig. 1) comprises several interlocking,…

A fast-growing tree, Ochroma pyramidale (also known as O. lagopus), which is widely distributed in tropical America, especially in Ecuador. Balsa (Ochroma pyramidale; also, O. lagopus) belongs to the mallow family, Malvaceae, in the order Malvales.…

The branch of ecology that focuses on the evolutionary causes of variation in behavior among populations and species. The scientific study of behavioral ecology investigates how changes of behavior are influenced by ecological factors (Fig. 1).…