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A major plant hormone that plays an important role in plant growth and development. Abscisic acid (ABA), with a chemical formula of C15H20O4 (Fig. 1), is one of the most significant hormones found in plants. It is responsible for regulating various…

Habituation to a specific practice, such as drinking alcoholic beverages or using drugs (for example, heroin, cocaine, or amphetamines), and disorders characterized by the chronic use of a drug, alcohol, or similar substance. Addiction and addictive…

Any disorder of recognition. Agnosia is a rare neurological condition in which an individual fails to recognize and identify persons or objects (see illustration). Typically, agnosia is the result of damage to specific areas of the brain.…

A disease of the nervous system characterized by a progressive dementia that leads to profound impairment in cognition and behavior. Dementia occurs in a number of brain diseases where the impairment in cognitive abilities represents a decline from…

A significant, yet relatively selective loss of memory. Amnesia is a type of memory loss, often resulting from brain disease or injury (see illustration). The inability to remember can be temporary or permanent. In general, amnesia can be…

One of the three living orders of the class Amphibia, encompassing the frogs and toads. Anura is the largest order of amphibians (class Amphibia), containing more than 7000 species of frogs (Fig. 1) and toads. Because members of the order Anura…

A disorder of language acquired as a result of brain disease. Aphasia is impairment in the use of spoken or written language caused by brain disorders (see illustration) that cannot be explained by paralysis or incoordination of the articulatory…

An impairment in the performance of voluntary actions despite intact motor power and coordination, sensation and perception, and comprehension. Apraxia is a neurological condition in which there is difficulty with skilled tasks or learned movements…

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…

Bats are members of the order Chiroptera, which is the second-largest order of living mammals. The geographic distribution of these flying mammals is tremendous as well, ranging from the limit of trees in the Northern Hemisphere to the southern tips…

Any of several leguminous plants, or their seeds, long utilized as food by humans or livestock. There are more than 40,000 varieties of beans, with only a small number of these being mass-produced for human or animal consumption. In particular,…

A taxonomic order of insects comprising the cockroaches and termites. The order Blattodea, also referred to as Blattaria, contains at least 4500 species of cockroaches (Fig. 1) and 3000 species of termites. Previously, termites were assigned to a…

The branch of biological science that embraces the study of plants and plant life. Botany is the scientific study of plants (see illustration), encompassing investigations of plant anatomy, physiology, genetics, phylogeny, ecology, pathology, and…

Terrestrial and aquatic animals that are capable of excavating holes in the ground for protection from adverse environmental conditions, as well as for storing food. Burrowing animals are uniquely adapted species, having the capacity to dig burrows…

A member of the mammalian family Camelidae in the order Artiodactyla. Camels are even-toed, hoofed mammals (ungulates). There are three extant camel species: the Bactrian camel (Camelus bactrianus; Fig. 1), the wild Bactrian camel (C. ferus), and…