2.5 Parasitism Flashcards
Summarise schistosomiasis.
Schistosomes reproduce sexually in the human intestine.
The fertilised eggs pass out via feaces into water where they develop into larvae.
The larvae then infect water snails, where asexual reproduction occurs.
This produces another type of larvae which escapes the snail and infects humans wading in the water.
State the difference between a definitive and intermediate host.
A definitive host is where a parasite reaches sexual maturity, where as an intermediate host is required for a parasite to complete its life cycle.
Discuss the role of vectors in transmitting parasites.
While vectors do not cause disease themselves, they spread a parasite from host to host.
What are viruses?
Parasites.
Describe the transmission of ectoparasites and endoparasites.
Ectoparasites are usually transmitted by direct contact, whereas endoparasites are transmitted by vectors.
Describe two factors that increase parasite transmission rates.
Tropical climates and dense populations.
Describe a behavioural modification, how it is an extension of the parasite’s phenotype and how it is advantageous to the parasite.
Behavioural modification to a prey’s anti-predator behaviour is an extension of the parasite’s phenotype, which aids the parasite in completing its life cycle by spreading itself further.
Describe the clonal selection of lymphocytes in a specific response to parasites.
Clonal selection is part of the secondary response, in which the response is enhanced in terms of; speed of production, concentration in blood and duration.
Describe two examples of chemical secretions in the defence against parasitic attack.
Mucus and saliva both prevent the passage of parasite to the internal system, thus preventing infection.
What are Natural Killer cells
Natural Killer cells patrol the body for the secretion of the protein MHC. No secretion of this protein triggers the natural killer cell to produce cytotoxic chemicals, which induce apoptosis.
Where do antibodies gain their specificity?
Antibodies variable region creates specificity.
Describe how endoparasites have evolved to evade the immune system.
Evading detection includes integrating the genome of the parasite with the genome of the host.
Describe what is meant by herd immunity.
Herd immunity is the percentage of the population which has the vaccination, which reduces transmission rates.
Describe what is meant by the vaccine and why they may be difficult to produce.
Vaccines expose an individual to the parasites antigens, to elicit an immune response. Antigens may be weakened, partial or dead.
Some viruses may be difficult to culture in a lab.
