The ability to live in only a set parameter of conditions, as in the case of obligate parasites which require a host to complete their life cycle and reproduce.

Outdated or superceded.

The blocking out of, such as a tree occluding light under its canopy caused by its overhanging branches and leaves.

Sea water exceeding 200 metres in depth.

Pertaining to organisms in the ocean that migrate to other parts of the ocean, unlike the likes of salmon who migrate into freshwater environments to spawn.

An organism possessing 8 of each chromosome number for that species gene pool.

The part of the alimentary canal between the pharynx in the upper throat and the stomach where food can travel down further into the digestive system.

A female hormone produced in the ovary beginning at puberty, which promotes the presence of secondary sexual characteristics and is also found in small amounts in males.

The reproductive cycle in females coordinated by the pituitary gland and its hormone secretion which affects the availability of gametes readily available to be fertilised and maintains the presence of secondary sexual characteristics.

A type of fat which is in a liquid form at normal room temperature.

A short sequence of nucleotides.

Animals that feed on plant and animal matter as a means of getting nutrition.

A viral gene causing cancer induction.

The study of bird eggs.

Open Population

A population where gene flow can openly occur.

Another word for operon in biological terms.

A structural gene which is determined functional or non-functional by an operating and regulating gene. See operon model.

The model proposed by Jacob and Monod that describes the way certain genes are either active or inactive, depending on whether there is a need for them to be active.

The hypothesis is a prime example of effective and efficient biology at work, where resources are only used when needed. A more elaborate explanation of the operon hypothesis can be found in the control of growth and development tutorial.

Ideal, a situation where the best result is attained.

A more exact taxon than a class, the primates are an example of a taxon order. To further differentiate unique species, orders are divided into organisms respective families.

Any functional unit of an organism which combine forces to perform a common role en masse.

Sub-cellular structures that perform a role within each cell. These vary widely from the nucleus, containing all our genetic information, to the golgi apparatus which processes protein and secretes it in vesicles on demand by the cell.

Any living thing that exhibits living characteristics and is composed of one cell or more.

The part of embryonic development where the body's main organs develop.

A phosphate with insecticidal properties.

A biochemical pathway in the liver of mammals where excess ammonia produced by the breakdown of birds. The dedicated study of and factors affecting them.

Any gene that can be found in two or more different species that can be traced back to the same common ancestor.

A scientific instrument capable of measuring osmotic pressure.

Osmoreceptors can be found in the hypothalamus of many homiotherms, and are responsible for detecting changes

The regulation of water potential in an organism. Over many years, different species have developed evolutionary adaptations in relation to their environment due to the fact that any organism will always 'want' to have an ideal water concentration in its cells.

Essentially, osmoregulation works around the natural forces of concentration gradients and water potential. The body will initiate a variety of countermeasures that re-navigate the flow of water around our body and either promote water retention or promote the secretion of water, depending on what environment the organism in question is situated in. See the animal and plant water regulation tutorial pages for related information in regards to evolutionary adaptations regarding osmoregulation.

The movement of water through a selectively permeable membrane across a concentration gradient (from a high concentration to a low concentration).

The potential for water to move across a selectively permeable membrane, where the osmotic potential of pure water is 0 and any water movement is measured with a negative value.

Any of the bones in the middle ear. There are three in humans, namely the malleus, incus and stapes - also known as the hammer, anvil and stirrup.

The formation of bone matter over what would previously have been another tissue.

An opening in organic sponges that allow water to enter the organism.

The opposite of inbreeding, where reproduction occurs between organisms that have no distinct family ties.

Plural of ovum.

The organ in female mammals and types of plant that is responsible for the production of female gametes and also responsible for the secretion of some sex hormones like oestrogen.

The occurrence where humans excessively remove fish from their habitat due to their material and nutritional values, where the number of fish removed is greater than the new fish brought into the population via reproduction.

The tube responsible for transporting female gametes to an area where they can be readily fertilised.

The formation of female gametes from the ovarian follicle.

The functional female gamete produced by the ovarian follicle.

Oxidase is an enzyme which is capable of adding oxygen to a substance, where hydrogen is usually released as a by-product which can bind with oxygen to form water.

A reaction where electrons involved are lost from an atom, or the addition of oxygen to a substance. Oxidation releases energy when the substances bond with a hydrogen atom is broken. The term can also refer to a general increase in the proportion of oxygen in a molecule. This may not necessarilly involve adding more oxygen to a molecule, as removing other types of atom would naturally increase the amount of oxygen.

A gas with an atomic weight of 14 that contributes to 21% of the total gasses in the atmosphere. Oxygen is essential to animals, where the presence of it allows aerobic respiration and thus maximise the amount of energy created from one molecule of glucose. Respiration is around 10 times more efficient in the presence of oxygen.

The continuous cycle of oxygen through the environment and biochemical pathways of organisms.

A situation where hard working tissues require more oxygen than they have available, which results in a 'debt' of oxygen. When this is the case, anaerobic respiration occurs.

Pertaining to the production of oxygen, e.g. photosynthesis is responsible for producing oxygen as a by-product.

Oxygenated haemoglobin.

A type of hormone produced by the pituitary gland which causes contraction of the uterine wall, and is found dur.