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steve Flashcards

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Biology 101 flashcards
1
Q

What percent of human pathogens are generalists that infect multiple hosts?

A

60%

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2
Q

What percent of carnivore pathogens are generalists that infect multiple hosts?

A

90%

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3
Q

In terms of only human pathogens, what is more likely to be a generalist, ermerging diseases or old diseases?

A

Old diseases

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4
Q

2 hotspots of pathogen richness

A

South America and Africa

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5
Q

What kind of transmission is single host-pathogen system?

A

Density dependent transmission

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6
Q

What type of transmission is beta11 and beta22

A

Intraspecific

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7
Q

What type of transmission is beta12 and beta21

A

Interspecific

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8
Q

2 scenarios of cross species transmission

A

At least one interspecific transmission non existing, mutual interspecific infection

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9
Q

The first scenario of cross species transmission says that what?

A

Pathogen can only persist if it can persist on one host alone

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10
Q

What is the spillover effect?

A

One host is capable alone of supporting the pathogen - i.e. it “spills over” into the second host resulting in some level of infection in that host

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11
Q

2 different ways scenario 2 of cross species transmission

A

Interspecific transmission < intraspecific transmissions, interspecific transmission > intraspecific transmission

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12
Q

If interspecific transmsiiions < intraspecific transmission, what allows the pahtogen to persist?

A

Two host densities combine

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13
Q

What scenario of mutual interspecific transmission allows the pathogen to exist in the least abundance?

A

Interspecific > intraspecific

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14
Q

Example of pathogen spill-over study

A

A. fatua that is a good host for barley yellow dwarf virus

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15
Q

What did the A. fatua study find?

A

Pathogen spill-over strongly increased pathogen prevalence in the other plants in the community

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16
Q

Within density-dependent transmission, what does pill-over dynamics do to host population density and fitness?

A

Decreases it

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17
Q

Within density-dependent transmission, what kind of interactions between host populations are mediated by the pathogen?

A

Negative (indirect)

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18
Q

Within density-dependent transmission, what does an increase in one host due to pathogen prevalence in the other host? Host density?

A

Increases, decreases

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19
Q

What does the theory of amplification effect say?

A

Multiple hosts could facilitate pathogen persistence and amplify pathogen abundance

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20
Q

What is the main study showing support for the amplification effect?

A

Lyme disease vs bird host diversity

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21
Q

What kind of pathogens are most interspecific pathogens?

A

Vector transmitted

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22
Q

Cross-species transmission is usually what kind of transmission?

A

Frequency-dependent

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23
Q

Within frequency-dependent transmission, what effect does a second host have on a pathogen?

A

Makes its persistence less likely

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24
Q

What is the dilution effect and what type of transmission does it deal with?

A

Host numbers dilute per capita transmission rate of frequency-dependent transmission

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25
Q

Example of dilution effect

A

West Nile virus

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26
Q

More or less disease: Additive species and frequency-dependent transmission

A

Less

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27
Q

More or less disease: Substitutive species and frequency-dependent transmission

A

Less

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28
Q

More or less disease: Additive species and density-dependent transmission

A

More

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29
Q

More or less disease: Substitutive species and density-dependent transmission

A

Less

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30
Q

True or false: Multi-host systems can either increase or decrease the probability of persistence of a pathogen dependent on transmission mode

A

True

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31
Q

True or false: Most cross species infection follows density-dependent transmission type

A

False

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32
Q

True or false: Increased biodiversity usually increases disease prevalence and risk of infections

A

False

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33
Q

True or false: Frequency-dependent transmission pathogens can drive a single host to extinction

A

True

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34
Q

3 general patterns of dilution effect

A

Sharing a pathogen can rescue a host from extinction, most likely if second host is a “bad” host for the disease, extinction unlikely since it requires high interspecific transmission rates than intraspecific rates

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35
Q

2 ways that sharing a pathogen can rescue a host form extinction

A

Frequency-dependent dilution effect, dilution effect exceeds interspecific infection

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36
Q

Animal(s) where increased species richness increase lyme disease prevalence; animal(s) where increased species richness decreases lyme disease prevalence

A

Birds; mammals and lizards

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37
Q

3 conditions where positive effects of hosts sharing pathogens are likely to be seen

A

Alternative host reduces intraspecific transmission rate in other host, alternative host is more resistance to disease, interspecific transmission rates are lower than intraspecific transmission rates

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38
Q

What pathogen causes lyme disease?

A

Borrelia burgdorferi

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39
Q

What is lyme disease transmitted by?

A

Black legged tick

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40
Q

Addition of non-human host to “siphon” vector meals away from humans

A

Zooprophylaxis

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41
Q

When a host is asymptomatic and not infectious

A

Latent

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42
Q

When a host is asymptomatic and infectious

A

Carrier

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43
Q

Time from infection to symptoms

A

Incubation period

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44
Q

Time from infection to transmission

A

Latent period

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45
Q

2 meanings of the word “virulence”

A

Measure of disease severity once host is infected, measure of the pathogen’s ability to infect the host

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46
Q

3 by-products of pathogen adaptation

A

Direct use of host resources for growth and reproduction, damage during growth and multiplication, damage during transmission

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47
Q

2 by-products that are incidental to pathogen adaptation

A

Long-term damage well after transmission, suppression of host defenses against other pathogens

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48
Q

True or false: use of host nutrients for growth and reproduction is frequently not a major reason for pathogenesis

A

True

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49
Q

3 exceptions to the theory that using host nutrients for growth and reproduction is not a reason for pathogenesis

A

Bacteriophages, parasitioids, macro-parasites

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50
Q

3 examples of damage during growth and reproduction within host that damages humans

A

Malaria, flesh-eating bacteria, gangrene

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51
Q

Plant pathogen that needs living tissue to reproduce

A

Biotrophic

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52
Q

Plant pathogen that kills tissue and feeds on dead remains

A

Saprotrophic

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53
Q

4 examples of damage during transmission of pathogen

A

Sleeping sickness, syphilis, cholera, brucella ovis

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54
Q

What is brucella ovis?

A

STD that causes abortions in cows; returns cows to oestrus and mating

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55
Q

2 examples of damage occurring well after infectious period that is non-adaptive for a pathogen

A

Tertiary syphillis, atheroscelerosis

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56
Q

What is tertiary syphilis?

A

Formation of soft tumor like balls of inflammation in tissue

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57
Q

What is atheroscelerosis?

A

hardening of arteries caused by pneumonia

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58
Q

Example of inactivation of host defenses against other pathogens

A

AIDS

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59
Q

3 ways fever combats disease

A

activates immune system, lowers iron concentration in blood, slows bacterial growth

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60
Q

6 ecological or behavioral resistances

A

active repulsion, cleaning, avoidance of infected sites, avoidance of infected individuals, social structure, self medication

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61
Q

Example of herding and parasite avoidance

A

Behavior of horses to avoid horseflies

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62
Q

Physiological/biochemical resistance that is there all the time

A

Constitutive

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63
Q

Physiological/biochemical resistance that is induced by the presence of the pathogen

A

Inducible

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64
Q

2 advantages of constitutive defense

A

Pre-emptive, no time delay

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65
Q

3 disadvantages of constitutive defense

A

Operate in absence of pathogen, difficulty in specificity, mechanisms may act as cues for specialized pathogens

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66
Q

Example of constitutive defense in humans

A

Ciliated cells in upper respiratory system

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67
Q

4 advantages of inducible defense

A

Only expressed when needed, valuable for “costly” defenses, can be “tailored”, some only effective when inducible

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68
Q

3 disadvantages of inducible defense

A

requires prior exposure, costs of constructing system, self-damage costs

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69
Q

Main problem with inducible defense

A

Distinguishing pathogen from self

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70
Q

3 examples of harmless nonself

A

Food, harmless organisms in environment, genetically different individuals of same species (e.g. sperm, offspring)

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71
Q

3 mechanisms of non-self recognition

A

Be a systematist, label self, generate cells that attack everything but remove those that recognize self

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72
Q

Reject other individuals based on differing taxon characteristics

A

Systematist

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73
Q

Reject unlabelled individuals

A

Label Self

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74
Q

Example of cells that attack everything, but remove those that recognize self

A

Vertebrate immune system

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75
Q

2 ways hosts distinguish bacteria from self

A

Cell wall constituents, flagellin

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76
Q

2 ways hosts distinguish fungi from self

A

cell wall and membrane constituents

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77
Q

Example of a host labeling self and rejecting unlabeled

A

Methylate DNA, degrade un-methylated DNA

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78
Q

Example of an “island effect” - too low genetic diversity resulting in outbreak of disease

A

Tasmanian devils with low diversity of MHCs

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79
Q

4 factors that constrain directional selection on host resistance

A

Lack of genetic variation in host, cost of resistance, heterozygote advantage, frequency dependent selection

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80
Q

How might a resistant host have lower fitness than a susceptible host?

A

Poorer competitor, lower fecundity, slower growth, delayed maturity

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81
Q

What can small resistance costs lead to?

A

Maintenance of genetic polymorphism

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82
Q

Instances where it is better to have two different alleles than a homozygous genotype

A

Heterozygote advantage

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83
Q

Why is heterozygote advantage actually advantageous?

A

Ideally, you can defend against 2x as many pathogens

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84
Q

Example of heterozygote advantage in animals

A

Harbor seals resistant to lung-worm

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85
Q

Example of heterozygote advantage in humans

A

Sickle cell anemia

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86
Q

What does the diversity of MHC receptors determine?

A

How many antigens the immune system can recognize

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87
Q

3 reasons why do MHC genes undergo rapid evolution?

A

Pathogens continually evolving, new pathogens have non-recognizable antigens, might allow host response to unpredictable and frequent disease outbreaks

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88
Q

What type of MHC diversity has the highest fitness?

A

Intermediate

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89
Q

What happens when MHC diversity is too low?

A

Not good enough to deal with novel pathogens

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90
Q

What happens when MHC diversity is too high?

A

Autoimmune responses

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91
Q

What is frequency dependent selection

A

Fitness of different genotypes depends on their relative frequencies

92
Q

How does frequency dependent selection operate?

A

Pathogens adapt to infect most “common” genotype, and make it rare, leading to cyclical dynamics

93
Q

2 predictions of red queen hypothesis

A

Changes in host genotype frequency should lead to time-lagged changes in infection frequency, parasites should be most infective in common hosts genotypes

94
Q

What does pathogens selecting for increasing host defenses and hosts selecting for new pathogen variants result in

A

Evolutionary “arms race”

95
Q

Ways that pathogens are able to win evolutionary arms race

A

faster generations, larger populations, higher mutation rates, lateral gene transfer

96
Q

Way that hosts are able to win evolutionary arms race

A

Larger genome

97
Q

What did the Lenski experiment try to solve?

A

The evolutionary arms race using lab cultures to investigate bacteria vs phage

98
Q

Change in gene frequencies over time

A

Evolution

99
Q

Gradual non-random process by which heritable traits that increase organism’s fitness in a given environment are more favored than less beneficial traits

A

Natural Selection

100
Q

2 assumptions made when using pathogens as evolutionary agents

A

Pathogens exert selective pressure on hosts by causing differential survival or reproduction, selection leads to changes in gene frequencies in the host

101
Q

3 things that parasite-mediated selection requires

A

Parasite numbers vary among individuals in population, variation parasite number must be associated with variation in fitness, trait to be mediated must co-vary with parasite number

102
Q

Which of the 3 ways of parasite-mediated selection is not common

A

Trait to be mediated must co-vary with parasite number

103
Q

2 things that parasite-mediated evolution requires

A

Parasite mediated selection, heritability of trait of interest

104
Q

What happens when variation is not heritable?

A

Selection without evolution

105
Q

The potential for evolution under particular conditions

A

Heritability

106
Q

How does one measure heritability

A

h^2, but difficult

107
Q

A mutation in what receptor causing the HIV resistance?

A

CCR5

108
Q

Where were mutations in the CCR5 gene first seen?

A

Central Europe

109
Q

A mutation in what gene causes sickle cells

A

Hemoglobin gene

110
Q

2 long term advantages of sexual reproduction

A

Populations without sex go extinct, recombination acts as a repair mechanism for deleterious mutations

111
Q

2 short term advantages of asexual reproduction

A

Adaptation to variable abiotic environments, adaptation to ever changing pathogen pressures

112
Q

Which has a reduced BYDV infection rate: sexually produced progeny or asexually produced?

A

Sexually produced

113
Q

What is the abundance of trematode prevalence among snails determined by?

A

Abundance of birds

114
Q

How does mate choice affect disease spread?

A

Direct assessment of disease status

115
Q

2 exaggerated secondary sexual characters that are used as indicators of disease status

A

Bright plumage, active courtship displays

116
Q

2 assumptions for parasite-mediated sexual selection

A

Health status is reflected in secondary sexual characteristics, females choose males with such characteristics to obtain “good genes”

117
Q

Do swallows get a lot of diseases?

A

YES!!!

118
Q

Highest prevalence among swallows

A

Ornithonyssus (mite)

119
Q

How does disease among swallows manifest itself in sexual selection?

A

Tail feathers grow less on diseased swallows, with tail length direct indicator of disease level

120
Q

What does the fact that offspring of males with longer tails having fewer mites independent of where the offspring were raised suggest

A

More genetically resistant

121
Q

True or false: sexual reproduction is intrinsically costly

A

True

122
Q

True or false: Progeny produced by asexual reproduction have a direct ecological advantage over sexual progeny

A

False

123
Q

True or false: Sexual selection provides faster mechanism for evolution of host resistance

A

True

124
Q

3 ways that conventional wisdom, “Parasites evolve to become benign” fail

A

sleeping sickness, river blindness, insect mushrooms

125
Q

What happens to someone infected with sleeping sickness

A

Alters circadian rhythm, leads to coma and death

126
Q

What happens to someone infected with river blindness

A

Permanent blindness

127
Q

What happens to an insect that is infected with insect mushrooms

A

Fungi cause hosts to fly or crawl to high spots and then die so spores can go further

128
Q

True or false: Parasites that rely on host mobility or behavior should be less virulent than those that are vector-transmitted

A

True

129
Q

If virulence is costly, why be virulent at all?

A

Virulence often co-varies with other factors that carry direct beneits

130
Q

Example of virulence direct benefits

A

Increased numbers within a host increase the likelihood of spreading to a new host

131
Q

What ultimately determines optimal virulence of a pathogen?

A

Fitness curve between virulence and parasite fitness

132
Q

True or false: shape of fitness curve (virulence vs parasite fitness) is unknown for almost all pathogens

A

True

133
Q

What is myxoma?

A

DNA virus that infects rabbits and causes tumors

134
Q

2 ways that virulence is altered

A

Hosts evolve, spatial structures

135
Q

How does spatial structure alter virulence?

A

Spatial clumping decreases virulence

136
Q

What does spatial clumping decrease virulence?

A

CHanges in transmission virulence trade-off

137
Q

What does old Paul Ewald have to say about virulence?

A

Transmission strategies determine optimal level of virulence, parasites that rely on host mobility should be less virulent than those that are vector-transmitted

138
Q

How does the tragedy of the commons apply to virulence?

A

If another pathogen has invaded your host, you should use up the host resources as fast as possible so your competitor doesn’t get them

139
Q

What prediction can be made in terms of tragedy of the commons applied to virulence?

A

Pathogens in mixed infections should have higher virulence than those in single-clone infections

140
Q

True or false: Pathogens always try to maximize their transmission rates

A

True

141
Q

True or false: Evolution of virulence driven by trade-off between costs and benefits

A

True

142
Q

True or false: Optimal virulence is usually at the maximum

A

False

143
Q

What can the virulence-transmission trade-off be altered by?

A

Environmental factors and transmission modes

144
Q

Evolutionary history of a group

A

Phylogeny

145
Q

How is phylogeny represented?

A

Tree

146
Q

Part of phylogenetic tree that is a point divergence between taxa

A

Node

147
Q

Part of phylogenetic tree that describes the relationships between taxa

A

Branch

148
Q

Part of phylogenetic tree that describes most recent common ancestor of all taxa

A

Root

149
Q

3 things that support for a phylogenetic tree comes from

A

Additional genes, additional taxa, evidence from geology

150
Q

3 uses of phylogenies in disease biology

A

pathogen relationships and control, understanding emerging diseases, tracing disease epidemiology

151
Q

3 things that understanding evolutionary relationships helps with

A

What control mechanisms are effective, culture techniques, features determining virulence

152
Q

What does molecular epidemiology seek to do

A

Trace spread of disease through populations using comparative gene sequence data

153
Q

What do successful strains of a pathogen have in common?

A

High rate of substitutions at particular codons

154
Q

Parasitism by an organism on or in another parasite

A

Hyperparasitism

155
Q

What is at the top of an Elton’s pyramid of predation

A

Secondary predator

156
Q

What is at the top of an Elton’s pyramid of parasitism

A

Hyperparasite

157
Q

2 examples of decreased virulence as a result of a hyperparasite

A

Virophage, dsRNA virus,

158
Q

3 examples of virophage

A

A. polyphaga, mamavirus, sputnik

159
Q

What are dsRNA viruses?

A

Viral-like genomes, often naked RNA molecules

160
Q

Example of dsRNA virus

A

Chestnut blight

161
Q

What does chestnut blight do?

A

Destroy bar, causing death of tree

162
Q

Example of increased virulence as result of hyperparasite

A

Bacteriophage

163
Q

Parasitism of members of the same species

A

Homoparasitism

164
Q

Where do most examples of homoparasitism occur?

A

Ticks

165
Q

What do homoparasitic ticks do?

A

Feed on hemolymph

166
Q

One way that hyperparasitism benefits humans?

A

Biological control agents to control insect pests

167
Q

How was mealybug invasions reduced?

A

Parasitoid wasps were released

168
Q

What is the fungus Ampelomyces used to control?

A

powdery mildew

169
Q

True or false: hyperparasitism is common

A

True

170
Q

True or false: hyperparasitism cannot alter virulence of their host

A

False

171
Q

What is a host shift?

A

Novel host-pathogen combination that become a new disease

172
Q

3 types of emerging infectious diseases

A

No transmission, transient host shift; transmission on new host, not self sustaining; transmission and self-sustaining

173
Q

3 factors favoring evolution in pathogens

A

Large numbers of source hosts, many contacts with new hosts, transmission in new host

174
Q

Why does large numbers of source hots favor evolution?

A

More mutations/variants

175
Q

Why does many contacts with new hosts favor evolution?

A

More selective trials

176
Q

Why does transmission in new host favor evolution?

A

More mutation and selection

177
Q

2 strategies to control host shifts

A

Limit number of generations in humans, limit population size

178
Q

What is serial passing experiments?

A

Experimental host shifts to determine how quickly pathogens adapt to new hosts

179
Q

True or false: once a host-shift occurs, specialization to new host is slow

A

False

180
Q

3 impacts of predators

A

Removal of sick, old, weak; reduce population of prey, result in cyclical population dynamics

181
Q

What does removal of “sick, old, weak” result in?

A

Reduction of infecteds within the population

182
Q

What does reducing population of prey result in?

A

Reduces contact rate for density-dependent transmission

183
Q

What does cyclical population dynamics result in?

A

COntact rate may vary dramatically over time

184
Q

True or false: specialist predators (i.e. that prey on only sick/weak) will reduce disease risk to humans

A

False

185
Q

How do generalist predators impact prey cycles?

A

Less likely to result in them

186
Q

2 characteristics of generalist predators

A

Can regulate prey populations to low levels over large areas, highly mobile

187
Q

What happens when predators don’t consume prey whole?

A

Spread infective stages of a pathogen

188
Q

2 non-consumptive effects of predators?

A

Changes in behavior, changes in physiology

189
Q

3 changes in behavior due to predators

A

clumping together, reduction in activity levels, changing habitat preferences

190
Q

2 changes in physiology due to predators

A

inducible defenses, re-allocation of energy

191
Q

2 things that are always at the top of the food chain

A

Parasites, pathogens

192
Q

If there are N species, how many connections of a food chain can there be?

A

N^2

193
Q

True or false: parasites are more specialized than predators or scavengers

A

True

194
Q

1 factor that increases the risk of secondary extinction of hosts

A

Complex life cycles of parasites

195
Q

What did Kuris and Lafferty find in a study on a California marsh?

A

Higher percentage of linkages of a food chain when parasites are considered

196
Q

True or false: Pathogen/parasite biomass exceeds that of top predators

A

True

197
Q

In a coastal marsh, what is the birth rate of trematodes in terms of elephants

A

One elephant/day

198
Q

What is the highest modern cause of species extinction

A

Habitat destruction

199
Q

What is the lowest modern cause of species extinction?

A

Disease

200
Q

True or false: Disease is likely to be lost when populations get small and/or isolated from each other

A

True

201
Q

2 general principles of disease-caused extinction

A

Host specific pathogens and parasites, generalist pathogens

202
Q

2 deterministic events that led to a decline in black footed ferrets

A

Loss of habitat/food resources, fragmentation/isolation

203
Q

3 stochastic events that led to a decline in black footed ferrets

A

Disease, very small population, inbreeding

204
Q

How did several bird species of Hawaii go extinct?

A

Bird malaria introduced by invasive birds and malaria

205
Q

What did Pedersen’s 2007 study on the assessment of threatened species find?

A

Direct evidence of parasites causing population declines or substantial negative effects on fitness

206
Q

2 types of IUCN classifications of “threatened”

A

By pathogens, by other factors

207
Q

True or false: most threatened species are closely related to domestic species

A

True

208
Q

What percent of threatening parasites can infect multiple hosts?

A

66%

209
Q

WHat percent of threatening parasites also infect domestic animals

A

96%

210
Q

Major threat to wildlife-diseases

A

Spill-over effects from domesticated animals

211
Q

Theory that says many invasive and pest species are successful because they have left their natural enemies behind

A

Enemy-escape hypothesis

212
Q

How does loss of diseases affect invasions?

A

Direct effect of population regulation, reallocation of resources from defense to reproduction

213
Q

What is a “healthy” ecosystem

A

Ecosystem persists and maintains productivity, biodiversity, resilience

214
Q

How can larval trematodes that parasitize snails be used by humans>

A

Measure habitat restoration success

215
Q

About how many cannibalistic species have been identified?

A

> 1500

216
Q

2 things that consumption of sick conspecifics often lead to

A

Infection, reduction in survival and growth

217
Q

Disease can only spread though cannibalism by?

A

Group cannibalism

218
Q

True or false: disease-mediated extinction is one side effect of canibalism

A

False

219
Q

True or false: disease transmission through “conspecific necrophagy” requires group cannibalism

A

True

220
Q

4 things of the war on infectious diseases

A

development of antibiotics, controlled vaccination programs, public health measures, social measures

221
Q

2 public health measures

A

public sanitation, chlorination of water supply

222
Q

2 social measures

A

improving housing, reducing poverty and over-crowding

223
Q

How many people die of infectious diseases per year

A

8 million

224
Q

Main cause of death by infectious diseases

A

Lower respiratory tract diseases

225
Q

Hot spots of emerging pathogens/diseases

A

India, Africa, southeast asia

226
Q

3 causes of antibiotic resistance

A

unnecessary prescriptions, use in animals, evolution

227
Q

First pandemic of 21st century

A

SARS

BIO 331 (1 decks)

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