Term
| give an example of zooprophylaxis? |
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Definition
| animals offer protection to humans because they divert pathogen carrying vectors from humans |
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Term
| where is lyme disease most prevalent? |
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Definition
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Term
| at what stage of tick development is lyme disease most likely to be transmitted? life cycle of borrelia burgdorferi? |
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Definition
| nymphal stage most likely to transmit bc infectious but too small to notice. life cycle- eggs hatch and larvae jump to mice or other small mammals, winter season goes by, grow to nymph stage and jump to other small mammals, molts over the summer to adult stage when it infects deer and large mammals in fall, winter goes by, jump off deer and lay eggs in spring |
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Term
| what is a dilution effect? (more good hosts, less diversity means disease more prevalent) what is disease risk and how does it relate to the density of infected vectors? |
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Definition
| disease risk is proportion of vectors infected and also density of infected vectors. dilution effect is when a diverse assemblage of relatively inefficient hosts reduces disease risk. more diversity means fewer good hosts so disease risk decreases |
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Term
| how is the number of lyme disease cases related to the number of different host species? |
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Definition
| more species richness means less incidence of lyme disease bc fewer of the available hosts are the really good ones so less efficient for the pathogen |
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Term
| what is the relationship between number of blood meals and resevoir competence? |
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Definition
| low resevoir competence (inefficient vector) means more blood meals must be taken to achieve transmission |
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Term
| how does fragmentation affect lyme disease? describe two possible mechanisms. |
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Definition
small fragments have higher lyme disease risk bc less species diversity in small patches. large areas have more species so the disease is not as dangerous.
1. loss of overall species diversity
2. increased mouse density as a result of predator loss. predators are often the first to go with human disturbance and subsequent loss of diversity
increased rodent pops and loss of diversity can increase human risk |
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Term
| how do the relative numbers of passerines and non passerines affect the prevalence of west nile cases in humans? |
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Definition
| the more non passerines the fewer the cases of west nile. passerines can carry the disease so when they are diluted there is less transmission and fewer cases in humans |
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Term
| how did the grassland plant species experiment show evidence supporting the dilution effect? |
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Definition
manipulated species richness and abundance in patches of grassland, allowed plants to be colonized by pathogens, assessed severity of disease in each patch.
as species richness increases, disease incidence decreases
as host abundance increases, disease incidence increases |
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Term
| how is the dilution effect different in frequency dependent transmission vs. density dependent transmission? |
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Definition
FD- adding host species decreases proportion of infecteds in a community, leading to decreased contacts
DD- adding species decreases the overall density of host |
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Term
| what is the main vector of west nile virus? when did it reach new york? what are the effects of west nile in humans? what type of virus? what is the distribution of the disease? |
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Definition
| vector is mosquitos. came to new york in 1999. probably introduced through imported plants or animals imported for food or pet trade |
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Term
| describe the west nile virus transmission cycle? |
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Definition
| mosquito transmits from birds to birds. incidental infections include humans and horses that can now house the pathogen but not transmit it |
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Term
| how does WNV manifest itself in humans? |
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Definition
| incidental infection from mosquito bite. no human-->human transmission |
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Term
| in what species is WNV most common. |
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Definition
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Term
| explain the janzen-connel hypothesis and what it tell us |
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Definition
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Term
| in terms of J-C hypothesis, what happens to seeds as distance from the parent tree is increased? pathogens? |
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Definition
| number of seeds declines with distance from parent tree |
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Term
| what did the greenhouse experiment tell us about whether fungus at the tree root was responsible for low seedling survival? |
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Definition
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Term
| how many species exist on earth? how many are described? |
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Definition
| 6 million species. 1.4 million have been described |
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Term
| what percent of known species are parasitic? |
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Definition
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Term
| what species are most threatened? |
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Definition
| amphibians, mammals, we don't know how many parasites are threatened |
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Term
| why is the % of parasites threatened likely to be large? |
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Definition
| bc they depend on the species that are also threatened and dying out |
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Term
| who is Carl Linnaeus and what did he do? |
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Definition
| developed binomial nomenclature classifaction |
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Term
| how does the biological species concept define species? how does this make it problematic for parasites to be classified as a species? |
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Definition
| groups of interbreeding populations that are reproductively isolated from other groups. many parasites are not reproductively isolated, lots of hybridization |
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Term
| how do parasites reproduce? |
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Definition
| clonal reproduction, selfing, sib-mating |
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Term
| some parasites exhibit tremendous genetic diversity. how do they accomplish this? |
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Definition
| diversity due to hybridization across species |
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Term
| what is the relationship between parasite and corresponding host extinction? |
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Definition
| when a host goes extinct usually the parasite goes along with it |
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Term
| is an ecosystem without parasites, 'healthy'? why or why not? |
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Definition
| ecosystems with parasites are more healthy bc they can increase or maintain good levels of diversity |
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Term
| how do parasites and disease impact host diversity? |
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Definition
| they can increase or decrease host diversity |
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