General

General

General nature or nature terms.

Contributors in General

General

A covalent bond in which atoms share electrons in an unequal fashion. The resulting molecule has regions with positive and negative charges. The presence of polar covalent bonds allows other polar ...

peristalsis

Biology; General

Involuntary contractions of the smooth muscles in the walls of the esophagus, stomach, and intestines that propel food along the digestive tract. Waves of muscle contraction in the esophagus that ...

peroxisomes

Biology; General

Membrane-bound vesicles in eukaryotic cells that contain oxidative enzymes.

pesticides

Biology; General

Chemicals that are applied to agricultural crops or domesticated plants and which kill or inhibit growth of insects.

petals

Biology; General

Usually brightly colored elements of a flower that may produce fragrant oils; nonreproductive structures that attract pollinators. Sterile leaf-like (white, colorless, but usually colored) structures ...

pyloric sphincter

Biology; General

The ring of muscle at the junction of the stomach and small intestine that regulates the movement of food into the small intestine.

parallel evolution

Biology; General

The development of similar characteristics in organisms that are not closely related (not part of a monophyletic group) due to adaptation to similar environments and/or strategies of life.