Glossary: O

obligate

Required.

ocean coasts, dunes

areas dominated by accumulations of sand which is shaped and formed by the action of wind and/or water. This habitat type also includes desert dune areas and lake coasts characterized by dune formation.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oceanic vent

Areas of the deep sea floor where continental plates are being pushed apart. Oceanic vents are places where hot sulfur-rich water is released from the ocean floor. An aquatic biome.

oceanodromous

Referring to fish that live entirely within oceans.

oestrus cycle

See estrus cycle.

ommatidia

The individual optical units of a compound eye. Found in Arthropoda.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

organism

a living thing (plant, animal, or microbe)

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

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osmoregulatory

referring to the means by which water content and salt and mineral concentrations of body fluids are controlled in animals and protozoans.

ossicle

any small bony or chitinous structure found in various skeletal parts of animals. Usually used to refer to the bones of the middle ear in vertebrates.

ostia

plural form of ostium, which is any small opening in a body organ or part. Usually used to refer to small openings or pores in the tissues of sponges (Phylum Porifera).

other polygyny

any form of polygyny that is not characterized as resource defense, female defense, or lekking polygyny

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

ovoviviparous

reproduction in which eggs develop within the maternal body without additional nourishment from the parent and hatch within the parent or immediately after laying.