background rate of extinction

The average rate of extinction that occurred before the appearance of humans or that occurs between mass extinction events. (Chapter 11)

benthic macroinvertebrates

Easy-to-see (not microscopic) arthropods such as insects that live on the stream bottom. (Chapter 15)

bioaccumulation

The buildup of substances in the tissue of an organism over the course of its lifetime. (Chapter 3)

biocentric worldview

A life-centered approach that views all life as having intrinsic value, regardless of its usefulness to humans. (Chapter 1)

biochar

A form of charcoal, produced when organic matter is partially burned, that can be used to improve soil quality. (Chapter 17)

biodegradable

Capable of being broken down by living organisms. (Chapter 7)

biodiversity

The variety of life on Earth; it includes species, genetic, and ecological diversity. (Chapter 1, 12)

biodiversity hotspot

An area that contains a large number of endangered endemic species. (Chapter 12)

biological assessment

The process of sampling an area to see what lives there as a tool to determine how healthy the area is. (Chapter 15)

biomagnification

The increased levels of substances in the tissue of predatory (higher trophic level) animals that have consumed organisms that contain bioaccumulated toxic substances. (Chapter 3)

biomass energy

Energy from biological material such as plants (wood, charcoal, crops) and animal waste. (Chapter 23)

biome

One of many distinctive types of ecosystems determined by climate and identified by the predominant vegetation and organisms that have adapted to live there. (Chapter 8)

biosphere

The sum total of all of Earth’s ecosystems. (Chapter 8)

biotic

The living (organic) components of an ecosystem, such as the plants and animals and their waste (dead leaves, feces). (Chapter 8)

biotic potential (r)

The maximum rate at which the population can grow due to births if each member of the population survives and reproduces. (Chapter 9)

boom-and-bust cycles

Fluctuations in population size that produce a very large population followed by a crash that lowers the population size drastically, followed again by an increase to a large size and a subsequent crash. (Chapter 9)

bottleneck effect

The situation that occurs when population size is drastically reduced, leading to the loss of some genetic variants, and resulting in a less diverse population. (Chapter 11)

bottom-up regulation

The control of population size by factors that enhance growth and survival (growth factors) such as nutrients, water, sunlight, and habitat. (Chapter 9)