Advanced higher biology key area 2.5 ( parasitism)

Antigenic variation

Change between different antigens during the course of infection of a host

B lymphocytes

White blood cells that produce specific antibodies in response to specific antigens

Competitive exclusion

Where the niches of two species are so similar that one declines to local extinction

Definitive host

The organism in or on which the parasite reaches sexual maturity

Ectoparasite

A parasite that lives on the surface of its host

Endoparasite

A parasite that lives within the tissues of its host

Epidemiology

The study of outbreak of infectious diseases

Extended phenotype

The expression os a parasites genotype into the genotype of its host by manipulating the host phenotype to facilite its transmition

Fundamental niche

The niche that is occupied in the absence of any interspecific competition

Gametocytes

The precursors of male and female gametes

Heard immunity threshold

The density of resistant hosts in the population required to prevent an epidemic

Hydrolytic enzymes

Any enzyme that catalyses the hydrolysis of a chemical bond

Inflammatory response

Injured or wounded areas become warm and red due to increased blood floe brining white blood cells for defence

Intermediate host

A host that is normally used by a parasite in the course of its life cycle and in which it may multiply asexually but not sexually

Latency

Viruses may escape immune surveillance by intergrating their genome into host genomes, existing in an inactive state

LEDC

Less economically developed country

Memory lymphocyte

Lymphocyte specific for a specific antigen, they are retained in the body following infection and can produce a secondary response to the same antigen

Natural killer cells

Lymphocytes responsible for destroying abnormal cells

Niche

A multi-dimensional summary of tolerances and requirements of a species

Non-specific defences

General response to infection, including phagocytosis

Phagocyte

White blood cells in non-specific defence, engulfing and destroying foreign antigens; may also present antigen to lymphocytes

Realised niche

The niche that is occupied in response to interspecific competiton

Resource partitioning

Where the realised niches are sufficiently different that potential competitors can co-exist

RNA retroviruses

Viruses that use the enzyme reverse transcriptase to form DNA

Specific cellular defences

Activity of the immune system in response to a particular pathogen, triggered by antigens located on the surface of cells

Transmittion

The spread of a parasite to a host

Vaccines

Contain antigens that will elicit an immune response

Vector

An organism that dos not cause disease itself but which spread the parasite from one host to another

Virulence

The harm caused to a host species by a parasite