The difference in concentration of a substance between two regions, which drives the movement of particles from high to low concentration.

Cavities or small pockets in certain plants or algae that contain reproductive organs, such as in marine algae.

The fertilization of an egg by a sperm cell, marking the beginning of pregnancy.

A model of evolution in which all members of a gene family evolve simultaneously, leading to coordinated changes across the entire gene set.

The degree to which two or more variables or conditions match or agree, often used in genetics to describe similarity in traits among individuals.

A simplified chemical formula that shows the elements in a compound and their proportions, omitting some of the bonds between atoms.

A mutation that expresses a phenotype only under specific environmental conditions or circumstances.

A learned response to a previously neutral stimulus that has been repeatedly associated with an unconditioned stimulus.

A rounded prominence at the end of a bone, typically part of a joint, where the bone articulates with another bone.

A type of photoreceptor cell in the retina of the eye that is responsible for color vision and visual acuity.