An interaction in which members of different species reduce one another's access to limiting resources. Shared location or a correlated population decline alone does not prove this mechanism.

Biological disturbance and mixing of sediment, including burrowing. It modifies habitats and can destroy or change surfaces that otherwise preserve body impressions and trace fossils.

Study of the ecological and evolutionary consequences of animal behaviour.

An interaction providing net benefits to both participants under specified conditions. It need not be obligatory or free of evolutionary conflict.

Dependence of interacting organisms on one another’s presence or activities in a specified environment. One-sided reliance should be distinguished from reciprocal dependence.

A persistent close association between organisms of different species. Such associations can be mutualistic, commensal or parasitic; symbiosis does not by itself mean mutual benefit.

Use of metabolites released or supplied by another organism. An initially incidental exchange can become specialized, but cross-feeding alone does not establish reciprocal dependence.

Movement potentially connecting populations or colonizing habitat. Movement alone is not gene flow: migrants must contribute inherited material to later generations.

Differential use of resources by coexisting organisms. It can reduce competition, but does not by itself measure the strength of competition that produced or currently accompanies it.

Overlap in a stated dimension of resource use or environmental requirements. Similarity of potential resource use is not a direct estimate of its demographic cost.

Evolutionary divergence associated with interactions between coexisting lineages. Testing it requires alternatives to pre-existing differences and environmental sorting.

A species moved by humans beyond its natural geographic range. Introduction is defined relative to location, not only national boundaries.

Establishment and spread of organisms into a new region, with effects dependent on community context and introduction history.

Conservation biology applies knowledge of ecology, genetics and evolution to maintaining biological diversity. It investigates threats such as habitat fragmentation, biological invasion and extinction, and tests interventions against explicit biological outcomes.

Protecting a patch of habitat and restoring connections between patches address different mechanisms: the first can increase available habitat, while the second can change dispersal and gene flow. Measuring both survival and later reproduction helps distinguish short-term occupancy from a persisting biological population.

Acceptability of an item as food to a specified consumer. Chemical concentration, willingness to attack, willingness to swallow and subsequent illness are different measurements.

Reduction in detection through resemblance to the visual or other sensory background. It is distinct from recognition as a defended organism after detection.

Life history theory explains how natural selection shapes the timing and allocation of growth, survival and reproduction. Age at maturity, offspring number and investment per offspring affect lifetime reproductive success, but cannot generally be improved independently because resources and time are limited.

A life-history trade-off is a constraint, rather than simply an observed negative correlation. Individuals acquiring more resources can both reproduce more and survive better, masking an underlying cost of allocation. An experiment that changes reproductive effort while measuring later survival or fecundity addresses the cost more directly than comparing naturally different individuals.

Conversion of molecular nitrogen into biologically accessible reduced nitrogen. Symbiotic fixation costs energy and must be distinguished from nitrate uptake.

An early developing organism, whose cells and tissues are undergoing coordinated specification, growth and morphogenesis.

The generation of biological shape through processes including tissue growth, cell movement and changes in cellular organisation.