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TERMGROUPDEFINITION
OBLIGATE ANAEROBENPBACTERIAPronunciation:

Etymology:

An obligate anaerobe is a cell that is poisoned in the presence of free oxygen.
OCELLUS (OCELLI)NANIMALS, PROTISTSPronunciation:

Etymology:

An ocellus (ocelli, pl.) is a simple eye or eyespot characteristic of many invertebrate groups.
ONCHOSPHERENANIMALSPronunciation:

Etymology:

An onchosphere (also called a coracidium) is the first encapsulated larval stage of certain tapeworms. It is ciliated and has 6 hooks.
OOCYSTNPROTISTSPronunciation:

Etymology:

An oocyst is an encysted zygote in many microbial eukaryotes (e.g. coccidians and heliozoans).
OOGAMOUSADJANIMALS, PLANTS, PROTISTS, FUNGIClick here
OOGONIUMNANIMALS, PLANTS, PROTISTS, FUNGIPronunciation & Etymology:

Oogonium is a specialized structure (gametangium) that contains the ovum or egg of an oogamous taxon.
OPERCULUM (OPERCULA)NANIMALS, PLANTSPronunciation:

Etymology:

Cap-like structure at the tip of the capsule.
OPISTHOKONTN OR ADJANIMALS, PROTISTSPronunciation:

Etymology:

Flagellum located in posterior position.
OPISTHOSOMANANIMALSPronunciation:

Etymology:

An opisthosoma is the chelicerate abdomen or the hind body region of the pogonophora.
ORAL PAPILLA (ORAL PAPILLAE)NPANIMALSPronunciation:

Etymology:

Oral papillae are paired finger-like appendages on either side of the mouth, which release a sticky substance used to capture prey in onychophorans.
ORDERNPSYSTEMATICSPronunciation:

Etymology:

Order is the taxonomic level that contains one or more families.
OSCULUM (OSCULA)NANIMALSPronunciation:

Etymology:

An osculum (oscula, plural) is the excurrent opening of a sponge.
OSTEOLATEADJPLANTSPronunciation:

Etymology:

Pericarp with hole on it.
OSTIUM (OSTIA)NANIMALSClick here
OVERTOPPINGNEVOLUTIONPronunciation:

Etymology:

Overtopping is a type of growth pattern in which there is unequal dichotomous branching. This produces a larger stem and a smaller lateral stem.
OVIDUCTNANIMALSClick here
OVIGEROUS LEGSNPANIMALSPronunciation:

Etymology:

Ovigerous leg are legs adapted to carrying eggs.
OVIPAROUSADJANIMALSPronunciation:

Etymology:

An oviparous (adj.) animal is one that releases eggs in its life cycle. They may be fertilized internally or externally.
OVULARYNPLANTSPronunciation:

Etymology:

An ovulary is the part of the pistil that contains the ovules. Sometimes this is called an ovary.
OVULENPLANTSPronunciation:

Etymology:

An ovule is a structure that contains the megagametophyte in seed plants. The megagametophyte remains within the megasporangium (the nucellus), which is surrounded by layers of integuments. After fertilization, the ovule develops into a seed.
OXIDASENPronunciation:

Etymology:

Oxidases are catalytic enzymes that use oxygen as an electron acceptor.
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