Parasitism

What is an ecological niche?

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

What is a fundamental niche?

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

What is a realised niche?

The niche that is occupied in response to interspecific competition

What is competitive exclusion?

When the niches of two species are so similar that one declines to total extinction as a result of interspecific competion

What is resource partitioning?

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

Unlike in a predator-prey relationship, the reproductive potential of the parasite is…

greater than that of the host

What is an ectoparasite?

A parasite that lives on the surface of its host

What is an endoparasite?

A parasite that lives within the tissues of its host

What is the Definitive host?

The organism on or in which the parasite reaches sexual maturity

What is a vector?

an organism that does not cause the disease itself, but carries the parasite from one host to another

What are viruses?

Parasites that can only replicate inside a host cell

What do viruses contain genetic material in?

In the form of DNA or RNA, packaged in a protective protein coat

What does the outer surface of a virus contain?

Antigens that a host cell may or may not be able to detect as foreign

Describe the Viral Life Cycle

Infection of a host cell with genetic material

Host cell enzymes replicate the viral genome

Transcription of viral genes and translation of viral proteins

Assembly and release of new viral particles

What are RNA retroviruses?

Viruses that use the enzyme reverse transcriptase to form DNA

What is transmission?

The spread of a parasite to a host

What is virulence

The harm caused to a host species by a parasite

How are ectoparasites generally transmitted?

Through direct contact

How are endoparasites of body tissues transmitted?

By vectors or by consumption of intermediate hosts

Factors that increase transmission rates

The overcrowding of hosts when they are at high density

Mechanisms such as vectors and waterborne dispersal stages, that allow the parasite to spread even if infected hosts are incapacitated

Name examples of host behaviours that is exploited and modified by parasites to maximise transmission

Alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour.

List non-specific defences

Physical barriers, chemical secretions, inflammatory response, phagocytes and natural killer cells destroying cell infected with viruses

Describe how memory lymphocytes work?

Initial antigen exposure produces memory lymphocyte cells specific for that antigen that can produce a secondary response when the same antigen enters the body in the future.

The secondary response is faster, produces a higher concentration of cells and increases duration

How do endoparasites evade detection?

By mimicking host antigens

How do some viruses escape immune surveillance?

By intergrating their genome into host genomes, existing as an inactive state known as latency

What is epidemiology?

The study of the outbreak and spread of infectious disease

What is the herd immunity threshold?

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

What do vaccines contain?

Antigens that will elicit an immune response

Host behaviour is often exploited and modified by parasites to…

maximise transmission

What do parasites often do to hosts to benefit parasite growth, reproduction and transmission?

Suppress the host immune system and modify host size and reproductive rate

What makes it difficult to find drug compounds that only target the parasite?

The similarities between the host and parasite metabolism

Where does overcrowding occur?

In refugee camps that result from war or natrual disaster, or rapidly growing cities in LEDC’s

What causes the rapid spread of parasites?

Overcrowding and tropical climates

What is the main practical control strategy to prevent spread of parasites?

Civil engineering projects to improve sanitation combined with co-ordinated vector control

How does improvement in parasite control affect children?

It will reduce child mortality and result in population-wide improvements in child development and intelligence and individuals have more resources for growth and development