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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).…

Fungi that exhibit the natural phenomenon of bioluminescence (the ability of an organism to emit visible light). Bioluminescence is the emission of photons of visible light by living organisms via the chemical reaction of molecular oxygen (O2) with…

A major mental disorder in which there are lifelong episodes of both mania and depression; also known as manic-depressive illness. Bipolar disorder, also termed manic-depressive illness or manic depression, is characterized by sudden and often…

A deciduous tree of the genus Betula, which is distributed over much of North America, in Asia (south to the Himalayas), and in Europe. Birch trees are assigned to the genus Betula. They belong to the family Betulaceae (which also contains alders,…

A group of steroidal plant hormones, typified by the compound brassinolide, that produce effects on plant growth and development. Plant hormones are naturally occurring organic molecules that regulate multiple aspects of plant growth and development…

Unwanted, aggressive behavior that involves a real or perceived power inequity. The behavior of bullying is often chronic and includes actions such as threats, spreading rumors, attacking someone physically or verbally, and purposefully excluding or…

A genus comprising yeastlike fungi that cause a variety of human diseases referred to as candidiasis. All Candida species are single-celled yeasts that are ovoid in shape and 3–5 μm in size, and they multiply by a process called budding. Most of…

Common pigments, typically of yellow, orange, or red hues, that serve in both light absorption and the protection against too much light in photosynthesis as well as in the vision process. Carotenoids comprise a class of labile, easily oxidizable,…

A linear polymer of (1→4)-linked β-d-glucopyranosyl units, and the most abundant of all naturally occurring substances. Cellulose is the main polysaccharide in living plants, forming the skeletal structure of the plant cell wall. Cellulose…

The generic name for any of the intensely green, blue, or purple pigments found in higher plants, algae, and photosynthetic bacteria that are an integral part of photosynthesis. Chlorophyll is the name given to any member of a group of important…

A tropical evergreen shrub or small tree of the genus Coffea (family Rubiaceae), a native of northeast Africa and adjacent southwest Asia, cultivated for the seeds (coffee beans) of its fruit. Members of the genus Coffea (Fig. 1) grow mainly between…

The internal structures and processes that are involved in the acquisition and use of knowledge, including sensation, perception, attention, learning, memory, language, thinking, and reasoning. The mental processes and behaviors that constitute…

Technology used to augment human mental capacity. In contrast, technology is widely used to augment human physical capabilities. We can move faster using cars, we can lift heavier weights using cranes, and we can even fly through the air using…

The ability to discriminate light on the basis of wavelength composition. Color vision is found in humans, in other primates, and in certain species of birds, fishes, reptiles, crustaceans, and insects. These animals have visual receptors that…

A learned response performed by a human or other animal to a signal that was previously associated with an event of consequence for that human or animal. A conditioned reflex, also known as a conditioned response, is an acquired response in which…

The state of being aware of one's own existence, of one's mental states, and of the impressions made upon one's senses. Consciousness is central to human existence, yet it has proved difficult to define and characterize. Typically, consciousness…