Definition: A recurring period of sexual receptivity and fertility in female mammals, often referred to as heat.

Example: The female dog is in oestrus and is ready to mate.

Definition: A large, nocturnal bird found in Central and South America that primarily eats fruit and is known for its ability to produce oil from its young.

Example: The oilbird is famous for its unique diet and the oil extracted from its young.

Definition: A sound made by a pig, often described as a grunting noise.

Example: The pig let out a loud oink when it was hungry.

Definition: A type of animal that lives in the forests of Africa, similar to a giraffe but smaller, with a reddish-brown body and white stripes on its legs.

Example: The okapi is known for its unique appearance and is often called the 'forest giraffe'.

Definition: A type of marine duck that has a black body and a white breast, commonly found in cold regions like the Arctic and North Temperate areas.

Example: The oldsquaw is known for its distinctive long tail and beautiful plumage.

Definition: A type of worm that belongs to a specific class of annelids, which includes earthworms and some small freshwater species. These worms do not have a specialized head and are often found in soil or water.

Example: The oligochaete plays an important role in soil health by aerating the ground and breaking down organic matter.

Definition: Describing an organism that feeds on a limited variety of food sources, particularly a small number of plants, often used in reference to insects.

Example: Some insects are oligophagous, meaning they only eat a few types of plants.

Definition: The third part of the stomach in animals that chew cud, found between two other stomach sections.

Example: In ruminants, the omasum plays a crucial role in the digestion process.

Definition: A type of animal that eats both plants and other animals, including certain mammals like hogs and hippopotamuses, as well as some birds.

Example: Bears are considered omnivores because they eat both fruits and fish.

Definition: A person or animal that eats both plants and animals.

Example: Bears are omnivores because they eat berries, fish, and insects.