Industrial country

The politically correct term for the rich countries of the world. The poor countries used to be called 'Third World' countries but are now referred to as non-industrial countries. Industrial melanism

In Britain, during the industrial revolution, some seventy different species of moth, which had superb camouflage colouring when resting on the bark of a tree, became very visible to insect-eating birds when the tree bark turned black from soot pollution. It was shown by breeding experiments that light-coloured moths could easily be changed to black, and vice versa. This is an example of the ability of reversible microevolution to change ecotypes. Infected seed

Infected seed has internal parasites that cannot be reached by surface chemicals which would control contaminated seed. Typically, covered smuts of cereals produce contaminated seed, while loose smuts of cereals produce infected seed. Infection

In a plant pathological context, this term is defined quite strictly. It is the contact made by one parasite individual with one host individual for the purposes of parasitism. See also: allo-infections, Auto-infection. Infectious

This term is normally taken to mean that a disease is caused by a parasitic organism, and that it can be transmitted from one host individual to another. But, in common usage, a laugh or a yawn can also be described as infectious. Infestation

This term is usually used in relation to insects but, in a wide epidemiological context, the terms infection and epidemic can be applied to all categories of parasite, including the insects. Inflexibility

See: Genetic inflexibility. Inflorescence

A flowering structure that has more than one flower. For example, the Umbellifereae are so called because each inflorescence is made up of many florets in an arrangement that is reminiscent of an umbrella. Inheritance

Inheritance is described as monogenic when the character in question is controlled by a single gene. Monogenic inheritance is qualitative in its effects and it leads to discontinuous variation in which a character is either present or absent, without any intermediates. Inheritance is described as polygenic if the character in question is controlled by many genes, called polygenes. Polygenic inheritance is quantitative in its effects, and it exhibits continuous variation with all degrees of difference between a minimum and a maximum. All polygenic resistance is horizontal resistance, but not all horizontal resistance is inherited polygenically.

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