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The Joshua tree (Yucca brevifolia) is a remarkable evergreen, treelike plant found only in the southwestern United States. It was named by Mormon settlers in the early 1800s. Upon seeing the limbs of this plant branching upwards to heaven, the…

An approach to management of natural resources that emphasizes how little is known about the dynamics of ecosystems and that, as more is learned, management will evolve and improve. Adaptive management is a systematic strategy that seeks to improve…

A model for the functioning of an agricultural system, with all inputs and outputs. An ecosystem may be as small as a set of microbial interactions that take place on the surface of roots, or as large as the globe. An agroecosystem may be at the…

Plant growth forms characteristic of upper reaches of forests on mountain slopes. In such an environment, trees undergo gradual changes that, though subtle at first, may become dramatic beyond the dense forest as the zone of transition leads into…

Intergrading regions on mountain slopes characterized by specific plant life forms or species composition, and determined by complex environmental gradients.Along an altitudinal transect of a mountain, there are sequential changes in the physiognomy…

Determination of the relative or absolute age of materials or objects by measurement of the degree of racemization of the amino acids present. With the exception of glycine, the amino acids found in proteins can exist in two isomeric forms called d-…

Collectively, members of the class Amphibia are facing massive reductions in total numbers, and the overall biodiversity of amphibians across the globe is under threat. Scientists have determined that global climate change and habitat destruction…

A method used by animals to conceal themselves from an enemy by appearing to be a section of the natural background. Animal camouflage is a strategy that animal organisms use to avoid or deflect the attacks of predators by misleading the latter's…

An ongoing current event in which a large number of living species are threatened with extinction or are going extinct because of environmentally destructive human activities. The Earth is presently in the midst of a mass extinction event. In the…

The observation, measurement, and explanation of human variability in time and space. Anthropology is a science concerned with the interrelations of the biological, cultural, geographical, and historical aspects of humankind, including modern human…

The systematic quantitative representation of the human body. Anthropometric techniques are used to measure the absolute and relative variability in size and shape of the human body. Instrumentation Depending on the objective, anthropometric…

The application of ecological principles to the solution of human problems and the maintenance of a quality life. It is assumed that humans are an integral part of ecological systems and that they depend upon healthy, well-operating, and productive…

The cultivation of freshwater and marine species for human purposes. Aquaculture, or aquatic farming, is concerned with the raising of animals and the harvesting of plants in freshwater and marine environments (Fig. 1). In other words, it is the…

The establishment of the temporal sequence of prehistoric events. An event can be defined as a duration of time during which certain features came together to form a set, for example, when certain materials were formed into an object (manufacturing…

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 parasitic disease caused by a roundworm typically found in raccoons that is transmissible to humans, other mammals, and birds. Baylisascaris procyonis is a parasitic roundworm of raccoons (Procyon lotor) and belongs to the order Ascaridida in…