natural selection

differential reproduction. Some individuals leave more offspring than others, contributing proportionally more gametes to future generations. If the phenotypic characteristics that contribute to greater reproductive success are transmitted through genes to offspring, those offspring should also have a reproductive advantage (assuming a stable environment). Phenotypic characters associated with more fertile individuals are thus augmented in the next generation, whereas characters associated with fewer progeny diminish in relative frequency. Selection thus does not necessarily reflect size, strength, or health, only the relative ability to produce fertile offspring.


[syn. scaphoid] a boat shaped tarsal bone that articulates proximally with the talus and distally with the medial, intermediate and lateral cuniforms.

New World monkey

primates that are in the suborder Platyrrhini whose natural habitats are located in Central and South America.


the environment that an organism lives in.

ninth rib

a false rib.

ninth thoracic

counting from the top, the ninth vertebra forming the mid-back.


refers to an organism primarily active during the night.


the point on a cladogram or phyletic chart that shows a line leading to two or more different species "branches" or separates from the main line; defined by synapomorphies.


an organism that continuously moves in search of resources for survival, such as food.

nutrient foramen

a small hole or opening in a bone through which a blood vessels or nerves pass.