Parasite Niche, Transmission and Virulence

Question 1

What is a parasite?

Answer 1

A symbiont that gains benefit in terms of nutrients at the expense of it’s hosts

Question 2

Define ‘ecological niche’

Answer 2

Multidimensional summary of tolerances and requirements of a species

Question 3

What does the ecological niche consider?

Answer 3

Abiotic factors (eg. temperature, salinity, pollution) and Biotic interactions (eg. predator-prey interactions, competition)

Question 4

What is the fundamental niche of a species?

Answer 4

Set of resources that it is capable of using in the absence of any interspecific competition

Question 5

What is the realised niche of a species?

Answer 5

Set of resources that a species actually uses in response to the presence of interspecific competition

Question 6

Describe the Competitive Exclusion principle

Answer 6

When two species are competing, their realised niches may be too similar, and one of the species will out-compete the other, leading to competitive exclusion

Question 7

What is resource partitioning?

Answer 7

When two species are competing and have different enough realised niches for them to co-exist then the species exploit different components of the same resource, reducing competition

Question 8

Give an example of a species that takes part in resource partitioning

Answer 8

Wading birds

Question 9

Give an example of an ectoparasite

Answer 9

Ticks, lice

Question 10

What are ectoparasites?

Answer 10

Parasites that live and feed on the surface of their host

Question 11

Give an example of an endoparasite

Answer 11

Tapeworm, Plamodium

Question 12

What are endoparasites?

Answer 12

Parasites that live and feed within their host

Question 13

Who has the bigger reproductive potential, the parasite or the host?

Answer 13

Parasite

Question 14

What is a degenerative parasite?

Answer 14

Parasite that lacks structures and organs found in other organisms

Question 15

Give an example of a degenerative parasite

Answer 15

A tapeworm

Lacks digestive system

Question 16

In what host does the parasite reach sexual maturity?

Answer 16

Definitive Host

Question 17

What is the intermediate host?

Answer 17

One in which the developmental stages of a parasite’s lifecycle occur

Question 18

What is the name for a species that plays an active part in the transmission of a parasite?

Answer 18

Vectors

Question 19

What is virulence, in relation to parasites?

Answer 19

The harm that a parasite causes to a host species

Question 20

State the two evolutionary stable strategies in relation to transmission and virulence

Answer 20

Low transmission, low virulence

High transmission, high virulence

Question 21

Why is high virulence, low transmission not an evolutionary stable strategy?

Answer 21

The parasite will not be transmitted sufficiently well to find new hosts and will die out

Question 22

Why is the high transmission, low virulence strategy not evolutionary stable?

Answer 22

Will be out-competed by a more virulent strain

Question 23

What transmission/virulence strategy does the common cold, rhinovirus use?

Answer 23

Low transmission, low virulence

Question 24

What are the three factors that increase transmission rates?

Answer 24

1. High Population Density
2. Use of Vectors
3. Water borne dispersal stages

Question 25

How does high population density increase transmission rates?

Answer 25

If hosts habitat is overcrowded, increases the chance of transmission by direct contact/ droplets

Question 26

What is the extended phenotype of a parasite?

Answer 26

When the parasite modifies the hosts behaviour

Question 27

What are the five categories of modifying host behaviour?

Answer 27

``` Host foraging Movement Sexual Behaviour Habitat Choice Anti-predator behaviour ```

Question 28

What is the advantage of a sexual phase in a parasite?

Answer 28

Produces genetic variation and so allows the rapid evolution needed in the Red Queen's race between parasite and host

Question 29

What is an advantage of an asexual phase in a parasite?

Answer 29

Rapid build up of a parasite population for dispersal into the next host

Question 30

What are the three factors that increase virulence?

Answer 30

1. Suppress the host immune system 2. Modify the size of the host 3. Reduce the host's reproductive rate

Question 31

How does suppressing the host immune system increase virulence?

Answer 31

Allows parasites to survive and reproduce in the host without being attacked by the host's defences

Question 32

How does modifying the host's size increase virulence?

Answer 32

Grows much larger so can support the asexual reproduction of more parasites

Question 33

How does reducing the host's reproductive rate increase virulence?

Answer 33

More of the host's energy can be directed to parasite reproduction

Question 34

What may cause a difference in host infection rates between members of the same population?

Answer 34

Sex Age Genotype Behaviour