death rate

the frequency of individuals in a population dying over a set period of time.


lost during development; an anatomical reference to primary or "baby" teeth (deciduous dentition).


when one or more base pairs is removed from a sequence in DNA as a result of replication errors or mutations.


a study of the increase or decrease in population size and what may have caused these changes (i.e., survival rates, death rates, reproduction, etc.).


the odontoid process located on the second cervical vertebrae (the axis).

dental formula

a standardized notation for the total number of incisors, canines, premolars, and molars in the upper and lower jaw seen in an organism. An adult human dental formula is expressed as


the chief tissue of a tooth; a tissue in the middle of the tooth that surrounds the pulp cavity and is covered by enamel on the crown and cementum on the root of the tooth.



deoxyribonucleic acid

a nucleic acid based on the five-carbon sugar deoxyribose in a double helix formation; found within chromosomes that carries genetic information. See also DNA.

derived trait

a recently acquired trait.

descent with modification

genetic material, including mutations, is pass from parent to offspring; the most basic principle of evolution.


refers to an artifact from a distinct time period and/or tool industry; a bone that is identifiable as a particular species.


primary ossification center, or shaft, of long bones.


a space between teeth.


the state of cells containing two copies of each chromosome. Humans are diploids.

directional selection

when one extreme is selected against, changing the average composition of the population by removing the variants at that one extreme.

disruptive selection

when the mean is selected against, driving the extremes of the population farther and farther from each other; may ultimately split the population into two separate populations.


a relative term used to describe a part of a limb that is farther from the attachment point to the trunk of the body; the opposite of proximal.

distal (dentition)

for premolars and molars, a relative term referring to the part of the tooth that is closer to the back of the mouth or throat; the opposite of mesial.


refers to an organism whose primary activities are during daylight hours.


[syn. divergent evolution] when genetic or character differences accumulate causing members of the same species to become increasingly different; the opposite of convergent evolution.


the abbreviation for deoxyribonucleic acid.

DNA sequence

the order of nucleotides in DNA.

dominant allele

an allele that is expressed in the phenotype regardless of is recessive alternative.


a relative term used for quadrupedal organisms (those that travel on four legs) to describe features that are closer to the spine or back of the body; opposite of ventral. The term posterior is a synonym commonly used when referring to bipedal hominin anatomy.


flexing the foot upwards towards the leg.