Biology

Protoclepsydrops

Protoclepsydrops — early Carboniferous amniote of the Joggins cliffs

Protocoleoptera

Protocoleoptera: the earliest beetles and their fossil evidence

Protoplasm

Protoplasm: the historical concept of living cell substance

Protoplast

Protoplast (wall-less cell): definition, isolation, uses, and distinctions

Protostome

Protozoa

Protozoa: single-celled eukaryotes, diversity, ecology and significance

Pseudogene

Pseudomonadales

Pseudomonadales: biology, ecology, and significance

Pseudomonas

Pseudomonas: ecology, biology, and clinical relevance

Pseudomonas aeruginosa

Pseudomonas aeruginosa: biology, clinical impact and control

Pseudopodia

Pseudopodia: cytoplasmic extensions for movement and feeding

Pseudosuchia

Pseudosuchia (crocodile-line archosaurs)

Pteropoda

Pteropoda: pelagic gastropods known as sea butterflies and sea angels

Pterygota

Pterygota: the winged insects and their descendants

Puberty

Puberty: Biological changes, timing, development and social aspects

Pubis (bone)

Pulmonary artery

Pulmonary artery: anatomy, function, and clinical significance

Pulmonary fibrosis

Pulmonary fibrosis: causes, symptoms, diagnosis and management

Pupa

Pupil (eye)

Purple bacteria

Putrefaction

Putrefaction: the microbial breakdown of organic matter

Qingjiang biota

Quadruped walk

Race (biology)

Race (biology): populations, differences, and taxonomic use

Biological race describes distinct populations within a species with modest morphological or genetic differences. The term contrasts with subspecies and has ecological, geographic,

Radiata

Radiolaria

Radioresistance

Radioresistance: biological resistance to radiation

Radius (bone)

Radula

Range (biology)

Range (biology): species distribution, patterns, measurement, and conservation

Range of motion

Range of motion (ROM): joint and muscle movement capacity

Rapid eye movement sleep

Rapid eye movement (REM) sleep

Recapitulation theory

Recapitulation theory (ontogeny recapitulates phylogeny)

Receptor (cell biology)

Receptor antagonist

Recognition

Recognition (cognitive process)

Rectum

Red algae

Red algae (Rhodophyta): biology, ecology and human uses

Red blood cell

Reflex

Reflex (automatic physiological response)

Regeneration

Regurgitation

Regurgitation: biological process, causes, and ecological roles

Relaxin

Renin

Replacement child

Replication

Replication: principles across science, biology, and computing

Reproduction

Reproduction (biology): sexual and asexual processes and their significance