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Question 1

The number of parasite species is unknown, but estimates suggest that:

Answer 1

• all free-living species are thought to be hosts for several parasite species
• at least half of all species are parasites

Question 2

How can parasites teach us about evolution?

Answer 2

• parasites/hosts show coevolution
• study of parasitic/non-parasitic genomes gives evidence of gene loss mechanisms and diversification
• parasites play major role in evolutionary appearance and maintenance of sexual reproduction in organisms

Question 3

Definition of parasitism…

Answer 3

parasitism is a symbiotic interaction between parasite and host (+/-)
a parasite gains benefit in terms of nutrients at the expense of its host

Question 4

Describe reproductive potential of parasite…

Answer 4

unlike in predator/prey relationship, the reproductive potential of the parasite is greater than that of the host

Question 5

What is an ecological niche?

Answer 5

a multidimensional summary of tolerances and requirements of a species

Question 6

What is a parasite niche like?

Answer 6

tend to have narrow niches as they are host specific
- as host provides many of parasite’s needs, many are degenerate, lacking in structure and organs found in other organisms

Question 7

What is an ectoparasite?

Answer 7

parasite that lives on surface of the host

Question 8

What is an endoparasite?

Answer 8

parasite that lives inside host’s tissues

Question 9

What is a definitive (primary) host?

Answer 9

the organism on or in which the parasite reaches sexual maturity

Question 10

What is the intermediate (secondary) host?

Answer 10

host needed for parasite to complete life cycle

Question 11

What is a vector?

Answer 11

it plays an active role in the transmission of the parasite and may also be a host

Question 12

What is a fundamental niche?

Answer 12

what a species occupies in absence of interspecific competing influences

Question 13

What is a realised niche?

Answer 13

is occupied in response to interspecific competition

Question 14

When does competitive exclusion occur?

Answer 14

where niches of two species are so similar that one declines to local extinction

Question 15

When does resource partitioning occur?

Answer 15

where realised niches are sufficiently different and potential competitors can co-exist

Question 16

What is resource partitioning?

Answer 16

where two competing species occupy different realised niches, compromising over resources and thus managing to exist simultaneously

Question 17

What is a microparasite?

Answer 17

of microscopic size (must use microscope to see)
e.g. bacteria, viruses, protozoans and fungi

Question 18

What is a macroparasite?

Answer 18

can be seen with the naked eye
e.g. ticks, nematodes, flukes

Question 19

What are common parasites?

Answer 19

protists, platyhelminths, nematodes, arthropods, bacteria and viruses

Question 20

What human diseases are caused by parasites?

Answer 20

schistosomiasis and malaria

Question 21

What causes schistosomiasis and where?

Answer 21

schistosomes in sub-tropical/tropical world regions

Question 22

Describe life cycle of schistosomes…

Answer 22

-schistosomes sexually reproduce in human intestine
- fertilised eggs pass out via faeces into water where they develop into larvae
- larvae then infect water snails where asexual reproduction occurs
- produces kind of motile larvae which escapes snail and penetrate human skin, entering the blood stream

Question 23

What are symptoms of schistosomiasis?

Answer 23

rash and cough, readily treated in UK

Question 24

What causes malaria?

Answer 24

plasmodium

Question 25

Describe life cycle of plasmodium...

Answer 25

- infected mosquito (vector) bites human - plasmodium enters blood stream - asexual reproduction occurs in liver and then red blood cells - when red blood cells burst gametocytes released into the blood stream - another mosquito bites infected human and gametocytes enter mosquito maturing into male/female gametocytes, allowing sexual reproduction to occur

Question 26

Why is it hard to create malaria vaccine?

Answer 26

plasmodium is very hard to culture

Question 27

What are malaria symptoms?

Answer 27

presents as headache and fever, treatable if detected

Question 28

How do parasites escape the host immune system?

Answer 28

sometimes mimic host antigens, hiding in liver cell so are undetected by immune system, allowing future recurrence also can modify the immune response

Question 29

What are viruses?

Answer 29

parasites that only replicate inside the host cell

Question 30

What is the structure of a virus like?

Answer 30

- genetic material, both DNA and RNA, packaged in protein coat - some viruses surrounded by phospholipid membrane derived from host cell materials - outer virus surface contains antigens that host cells may/may not detect as foreign

Question 31

What are retroviruses?

Answer 31

have genetic material that is RNA, use the enzyme reverse transcriptase to form DNA which is then inserted into host cell genome the viral genes are then expressed to form new viral products

Question 32

Give an example of a retrovirus...

Answer 32

HIV

Question 33

Describe the life cycle of a virus...

Answer 33

- infection of host with genetic material - host cell enzymes replicate viral genome - transcription of viral genes and translation of viral proteins - assembly and release of new viral particles

Question 34

What do viruses depend upon the host for?

Answer 34

- ATP - nucleotides - amino acids - enzymes

Question 35

What do viruses also do to the host cells?

Answer 35

they suppress host's own DNA replication and protein synthesis

Question 36

What is transmission?

Answer 36

the spread of a parasite to a host

Question 37

What is virulence?

Answer 37

the harm caused to host species by parasite

Question 38

When are transmission rates greatest?

Answer 38

- when hosts overcrowd, areas with high population density (cities) - when mechanisms, vectors/waterborne dispersal stages allow parasite to spread even if hosts (infected) are incapacitated

Question 39

How are ectoparasites transmitted?

Answer 39

through direct contact

Question 40

How are endoparasites transmitted?

Answer 40

by vectors or consumption of intermediate hosts

Question 41

How do parasite use host behaviours?

Answer 41

often exploited to maximise transmission e.g. foraging, movement, sexual behaviour, habitat choice, anti'predator behaviour

Question 42

What is an extended phenotype?

Answer 42

where host behaviour become part of parasite phenotype

Question 43

Give example of extended phenotype in toxoplasma..

Answer 43

the cat parasite toxoplasma gondii causes infected rodents to lose predator fear so cat catch easier, toxoplasma then sexually reproduces in cat gut

Question 44

Give example of extended phenotype in plasmodium...

Answer 44

female infected mosquitoes are more attracted to humans than non-infected ones

Question 45

Give example of extended phenotype in hairworm...

Answer 45

crickets jump into water when infected by hairworm, sot it can come out of cricket to continue its lifestyle adult horsehair worms are free-living in fresh water and damp soil parasitised crickets seek water as they think they are thirsty

Question 46

What may parasites modify in a host?

Answer 46

- host immune system - host size - host reproductive rate - host lifespan

Question 47

What does host modification do for the parasite?

Answer 47

tend to benefit parasite growth, reproduction or transmission host survival may actually increase with some levels of infection