2.5 parasitism Flashcards
how can endoparasites evade the immune system?
by mimicking host antigens to evade detection and modify the host immune responseto reduce their chances of destruction
what are some methods for parasite control?
civil engineering projects to improve sanitation (latrines, wells)
vector control (pesticides)
what must be reflected in the design of the vaccine?
antigenic variation
which enzymes, found in mucus, saliva and tears, and involved in the breakdown of bacterial cell walls?
hydrolytic enzymes
what does the parasite become part of by altering the host?
its extended phenotype
what can parasites do to the host to benefit its growth, reproduction and transmission?
suppress the host immune system and modify host size and reproduction rate
what can parasites alter about the host to maximise transmission?
host foraging, movement, sexual behaviour, habitat choice and anti-predator behaviour
which two factors increase transmission rates of a parasite?
overcrowding of hosts when they are at a high density
mechanisms such as vectors and waterborne dispersal stages (allow the parasite to spread even if infected hosts are incapacitated)
which two aspects of a parasite’s biology must we understand?
transmission - how they spread
virulence - the degree of harm they cause their host
what happens once a retrovirus has formed DNA?
it is inserted into the genome of the host cell
what are the stages of the viral life cycle?
host infected with genetic material
host cells replicate viral genome
viral genes and proteins transcribed and translated
new viral particles assembled and release
what can be found on the outer surface of a parasite?
antigens that a host cell may or may not be able to detect as foreign
what are some viruses surrounded by?
a phospholipid membrane derived from host cell materials
in which form do viruses contain genetic material?
of DNA and RNA, packaged in a protective protein coat
what happens second in the plasmodium life cycle?
red blood cells burst and gametocytes are released
what is fundamental niche?
the niche that it occupies in the absence of any interspecific competing influences
how can some viruses escape immune surveillance?
they can integrate their own genome into the genome of the host, remaining inactive until they are needed. this is called latency
what does antigenic variation allow?
the parasite to change between different antigens whilst affecting the host, which can allow for re-infection
what will improving parasite control help with?
reducing child mortality rates
improving child development and intelligence due to greater access to resources
what do the conditions in refugee camps mean for the coordination of treatment programmes?
they are difficult to achieve
what can refugee camps result from?
war, natural disasters or over-crowing cities in less economically developed countries
which conditions can cause parasites to spread more rapidly?
overcrowding and tropical conditions
what gives antibodies specificity to binding antigens?
they possess regions where the aminoacid sequence varies greatly betweendifferent antibodies
why can it be difficult to produce a vaccine against parasites?
they can be difficult to culture in a lab
why can it be difficult for drugs to solely target the parasite?
similar metabolisms of the host and parasite
what are the three main control measures for infectious diseases?
controlling transmission, drug therapy, immunisation
what do epidemiologists study?
the outbreak and pattern of infections diseases to determine the factors that affect the spread of infectious disease
what is immune surveillance?
a range of different white blood cells move around the body in blood vessels, continuously monitoring the state of the tissues
what is the role of NK cells?
identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis.
what does the low pH of the stomach, vagina and sweat gland do?
it helps to denature proteins of a pathogen, rendering it harmless
what are physical barriers responsible for?
blocking the entry of parasites
how do retroviruses from DNA from RNA?
using the enzyme reverse transcriptase
what is a retrovirus?
a virus that contains RNA instead of DNA
what are viruses?
parasites that can only replicate inside a host cell
what happens finally in the schistosome life cycle?
motile larvae now penetrates human skin and enters the blood
what happens thirdly in the schistosome life cycle?
larvae then infect the snail where asexual reproduction occurs
what happens second in the schistosome life cycle?
fertilised eggs are released in faeces into water
what happens first in the schistosome life cycle?
schistosomes produce sexually in the human intestine
what happens finally in the plasmodium life cycle?
another mosquito bites the human and the gametocytes are transferred into it where they mature into male and female gametes, allowing sexual reproduction to occur
what occurs first in the plasmodium life cycle?
plasmodium enters the bloodstream and reproduces asexually in the liver and red blood cells
what is a vector?
plays an active role in the transmission of the parasite and in some cases may be a host
what is the intermediate host?
a host that may be required for the parasite to complete its life cycle
what is the definitive host?
the host in which the parasite reaches sexual maturity
how are ectoparasites usually transmitted?
by direct contact
how are endoparasites usually transmitted?
by vectors/by consumption of the intermediate host
where do endoparasites live?
within the body/tissue of its host
where does an ectoparasite live?
on the surface of its host
why are parasites degenerate?
the host provides so many of its needs
what does it mean to say that parasites are degenerate?
they lack structures and organs found in other organisms?
why do parasites have a narrow (specialised) niche?
they are host specific
how is a parasitic relationship different to predator-prey?
the reproductive potential of the parasite is greater than that of the host
what is a parasite?
a symbiont that gains nutrients at the expense of its host
how can potential competitors co-exist if their realised niches are sufficiently different?
by resource partitioning
when does competitive exclusion occur?
when the niches of two different species are very similar that the resulting competition between them causes the population decline and local extinction of one
what is realised niche?
the narrower niche occupied in response to interspecific competition
what is a niche?
the multidimensional summary of tolerances and requirements of a species
