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2.5 a Flashcards

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1
Q

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

A
  • all free-living species are thought to be hosts for several parasite species
  • at least half of all species are parasites
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2
Q

How can parasites teach us about evolution?

A
  • 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
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3
Q

Definition of parasitism…

A

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

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4
Q

Describe reproductive potential of parasite…

A

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

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5
Q

What is an ecological niche?

A

a multidimensional summary of tolerances and requirements of a species

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6
Q

What is a parasite niche like?

A

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

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7
Q

What is an ectoparasite?

A

parasite that lives on surface of the host

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8
Q

What is an endoparasite?

A

parasite that lives inside host’s tissues

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9
Q

What is a definitive (primary) host?

A

the organism on or in which the parasite reaches sexual maturity

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10
Q

What is the intermediate (secondary) host?

A

host needed for parasite to complete life cycle

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11
Q

What is a vector?

A

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

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12
Q

What is a fundamental niche?

A

what a species occupies in absence of interspecific competing influences

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13
Q

What is a realised niche?

A

is occupied in response to interspecific competition

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14
Q

When does competitive exclusion occur?

A

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

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15
Q

When does resource partitioning occur?

A

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

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16
Q

What is resource partitioning?

A

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

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17
Q

What is a microparasite?

A

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

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18
Q

What is a macroparasite?

A

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

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19
Q

What are common parasites?

A

protists, platyhelminths, nematodes, arthropods, bacteria and viruses

20
Q

What human diseases are caused by parasites?

A

schistosomiasis and malaria

21
Q

What causes schistosomiasis and where?

A

schistosomes in sub-tropical/tropical world regions

22
Q

Describe life cycle of schistosomes…

A

-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

23
Q

What are symptoms of schistosomiasis?

A

rash and cough, readily treated in UK

24
Q

What causes malaria?

A

plasmodium

25
Q

Describe life cycle of plasmodium…

A
  • 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
26
Q

Why is it hard to create malaria vaccine?

A

plasmodium is very hard to culture

27
Q

What are malaria symptoms?

A

presents as headache and fever, treatable if detected

28
Q

How do parasites escape the host immune system?

A

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

29
Q

What are viruses?

A

parasites that only replicate inside the host cell

30
Q

What is the structure of a virus like?

A
  • 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
31
Q

What are retroviruses?

A

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

32
Q

Give an example of a retrovirus…

A

HIV

33
Q

Describe the life cycle of a virus…

A
  • 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
34
Q

What do viruses depend upon the host for?

A
  • ATP
  • nucleotides
  • amino acids
  • enzymes
35
Q

What do viruses also do to the host cells?

A

they suppress host’s own DNA replication and protein synthesis

36
Q

What is transmission?

A

the spread of a parasite to a host

37
Q

What is virulence?

A

the harm caused to host species by parasite

38
Q

When are transmission rates greatest?

A
  • 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
39
Q

How are ectoparasites transmitted?

A

through direct contact

40
Q

How are endoparasites transmitted?

A

by vectors or consumption of intermediate hosts

41
Q

How do parasite use host behaviours?

A

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

42
Q

What is an extended phenotype?

A

where host behaviour become part of parasite phenotype

43
Q

Give example of extended phenotype in toxoplasma..

A

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

44
Q

Give example of extended phenotype in plasmodium…

A

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

45
Q

Give example of extended phenotype in hairworm…

A

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

46
Q

What may parasites modify in a host?

A
  • host immune system
  • host size
  • host reproductive rate
  • host lifespan
47
Q

What does host modification do for the parasite?

A

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

advanced higher biology (17 decks)

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