Unit 2: Organisms and evolution KA 2.5: Parasitism Flashcards
define the term ecological niche
a multi-dimensional summary of tolerances and requirements of a species
example of a biotic tolerance (2)
-density of predators
-intensity of competition
example of biotic requirement (3)
-availability of prey
-availability of pollinators
-other ecological services
examples of abiotic tolerances (2)
-range of temperatures
-range of pH
example of abiotic requirements (1)
-suitable habitat features, such as flat rock for basking
define intraspecific competition
competition between members of the same species for the exact same resources
define interspecific competition
competition between members of different species for similar resources
what is a fundamental niche
the niche a species occupies in the absence of any interspecific competition
what is a realised niche
the niche occupied in response to interspecific competition
describe competitive exclusion
where the niches of 2 species are so similar that one species declines to local extinction
describe resource partitioning
where the realised niches become sufficiently different, potential competitors can co-exist by resource partitioning
what does degenerate mean in terms of parasites
the host provides so many of the parasites needs, many parasites are degenerate, lacking structures and organs found in other organisms
define ectoparasite
a parasite that lives on the surface of its host
define endoparasite
a parasite that lives within the features of its host
define a definitive host
the organism in/on which the parasite reaches sexual maturity, produces gametes or undergoes sexual reproduction
describe an intermediate host
intermediate hosts may also be required for the parasite to complete its life cycle
what is a vector
a vector plays an active role in the transmission of the parasite and may also be a host
what is the name of the parasite responsible for malaria
plasmodium
where does asexual reproduction occur in the lifecycle of the plasmodium parasite
in humans, within the liver then in red blood cells
what is released into the bloodstream when red blood cells burst in the lifecycle of the plasmodium parasite
plasmodium gametocytes
where does sexual reproduction occur in the lifecycle of the plasmodium parasite and what does that make this host
the mosquito, the definitive host
what is the name of the parasitic flatworms
schistosomes
where does sexual reproduction occur in the lifecycle of the schistosome parasite and what does this make that host
the human intestine, a definitive host
how do the fertilised eggs in the human intestine turn into larvae in the water
the fertilised eggs pass out via faeces into water where they develop into larvae
where does asexual reproduction occur in the lifecycle of the schistosome parasite
water snails
how do schistosomes get transmitted to humans
motile larvae penetrate the skin of a human that’s in the water and enter the bloodstream
what is in the centre of a virus
genetic material in the form of dna or rna
what surrounds the genetic material in a virus
a protective protein coat
what is on the outer surface of a virus
antigens, that a host cell may or may not be able to tell is foreign
what are some viruses surrounded by and what is it derived from
a phospholipid membrane, which is derived from host cell material
what are the stages of the life cycle of a virus inside a host cell
1) infection of the host with genetic material
2) Host cell enzymes replicate viral genome, transcription of viral genes and translation of viral proteins
3) assembly and release of new viral proteins
examples of what the host cell supplies a virus with (4)
-nucleotides
-amino acids
-ATP
-enzymes
example of a retro virus
HIV
what does RNA retrovirus use to from DNA
reverse transcriptase
define the term transmission
how parasites spread to the host
define the term virulence
how much harm parasites cause their host and the affect on the hosts fitness
factors that increase transmission rate (3)
-overcrowding of hosts
-mechanisms that allow the parasite to spread (vectors and waterborne dispersal)
-changes in host behavior
examples on how host behavior can be altered by parasites (5)
-foraging
-movement
-sexual behaviour
-habitat choice
-anti predator behaviour
examples of non behavioural changes parasites can cause in their host (3)
-suppress hosts immune system
-modify host size
-modify reproduction rate (in ways that benefit growth, reproduction and transmission)
state the term that describes how host behaviour becomes part of the parasite
extended phenotype
how are ectoparasites generally transmitted
direct contact
how are endoparasites generally transmitted
by vectors or consumption of intermediate hosts
example of a non specific physical defense against parasites (1)
-epithelial tissue-blocks the entry of parasites
example of a non specific chemical defense against parasites (2)
-hydrolytic enzymes in mucus, saliva and tears which destroy the cell wall
-low pH enviorments of the secretions of the stomach, vagina and sweat glands, which denatures the cellular proteins of pathogens
example of a non specific cellular defense against parasites
-inflammatory response
-phagocytosis
-natural killer cells
what happens in the inflammatory response when cells are damaged
-injured cells released signalling molecules (cytokines)
-this results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes to deal with any pathogens
describe the process of phagocytosis
killing of parasites using powerful hydrolytic enzymes contained in lysosomes, by engulfing them and enclosing them inside a vacuole
what do natural killer cells do
identify and attach to cells infected with a virus, releasing chemicals that lead to apoptosis
define lymphocytes
white blood cells produced from stem cells in the bone marrow
how is a clonal population of identical lymphocytes produced
antigen binding leads to repeated lymphocyte division, resulting in a clonal population of identical lymphocytes
what produces memory lymphocytes
initial antigen exposure
why are memory lymphocytes important for the secondary responce
antibody production is enhanced in terms of speed of production, concentration in blood and duration when the second response occurs
what is antigen mimicry
when an endoparasite copies the antigens of a self cell to evade detection from antibodies
what is antigenic variation
it allows the parasite to change between antigens over the course of infection of a host
what is latency in terms of viruses
when a virus integrates their genome into the genome of a host
the parasite will then become active again when the conditions are favourable
define the term epidemiology
the study of the outbreak of infectious disease
3 factors the the herd immunity threshold depends on
-type of disease
-the effectiveness of the vaccine
-the density of the population
why must vaccines reflect the antigenic variation found in parasites
vaccines that reflect the antigenic variation produce a range on antibodies, so remain effective
describe 2 reasons why it can be difficult to develop vaccines and treatments for parasitic infections
-the similarities between the host and the parasite can make it difficult to find drug components that only target the parasite
-some parasites are difficult to culture therefore its difficult to design vaccines
examples of possible parasite control strategies
- co-ordinated vector control
- civil engineering projects to improve sanitation
give two benefits to children when the spread of parasites is controlled
-reduced child mortality
-improved child development and intelligence
define the term herd immunity threshold
the density of the resistant host in the population required to prevent an epidemic
