2.5 Parasitism Flashcards Preview

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Flashcards in 2.5 Parasitism Deck (96)
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1
Q

what is a niche

A

the niche of an organism is the functional role that it plays within an ecosystem

2
Q

what is an ecological niche

A

a multi-dimensional summary of tolerances and requirements of a species

3
Q

what are the types of niches

A

fundamental

realised

4
Q

what is a fundamental niche

A

the niche that an organism occupies when there are no other species present competing for space or resources (no interspecific competition)

5
Q

what is a realised niche

A

the niche that an organism occupies when there is competition from other species (interspecific competition)

6
Q

what can interspecific competition (realised competition) lead to

A

competitive exclusion

7
Q

what is competitive exclusion

A

when two species are in intense competition with one another and the weaker of the two species declines or becomes locally extinct

8
Q

what can occur if the realised niches are sufficiently different

A

resource partitioning

9
Q

what is resource partitioning

A

where two species occupy different realised niches, allowing them to co-exist by compromising over resources

10
Q

what is parasitism

A

a symbiotic interaction between a parasite and its host (+/-)

11
Q

what does a parasite benefit in at the expense of the host

A

nutrients and shelter

12
Q

what is the difference between a predator-prey relationship and parasitism

A

the reproductive potential of the parasite is greater then that of the host

13
Q

why do most parasites have a narrow (specialised) niche

A

the are very host-specific

14
Q

what does hosts providing many of the parasite’s needs lead to

A

parasite being degenerate

15
Q

what does degenerate mean

A

lacking structures and organs found in other organisms

16
Q

what is an ectoparasite

A

a parasite which lives on the surface of its host

17
Q

what is an endoparasite

A

a parasite which lives within the tissues of its host

18
Q

how many hosts do parasites require to complete their cycle

A

some require 1

most require more than one

19
Q

what is a definitive (primary) host

A

host where parasite reaches sexual maturity

20
Q

what is an intermediate (secondary) host

A

the host that the parasite might require in order to complete its life cycle or as a means of transmission thus making it a vector

21
Q

what is a vector

A

the means of transmitting a parasite

22
Q

what role does a vector play

A

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

23
Q

what is the human disease malaria caused by

A

Plasmodium

24
Q

what is the first step in the malaria life cycle

A

an infected mosquito, acting as a vector, bits a human

25
Q

what is the second step in the malaria life cycle

A

Plasmodium enters the human bloodstream

26
Q

what is the third step in the malaria life cycle

A

asexual reproduction occurs in the liver and then in the red blood cells

27
Q

what is the fourth step in the malaria life cycle

A

when the red blood cells burst gametocytes are released into the bloodstream

28
Q

what is the fifth step in the malaria life cycle

A

another mosquito bites an infected human and the gametocytes enter the mosquito, maturing into male and female gametes, allowing sexual reproduction to now occur
the mosquito can then infect another human host

29
Q

what is the human disease schistosomiasis caused by

A

schistosomes

30
Q

what is the first step in the schistosomiasis life cycle

A

schostosomes reproduce sexually in the human intestine

31
Q

what is the second step in the schistosomiasis life cycle

A

the fertilised eggs pass out via faeces into water where they develop into larvae

32
Q

what is the third step in the schistosomiasis life cycle

A

the larvae then infect water snails where asexual reproduction occurs

33
Q

what is the fourth step in the schistosomiasis life cycle

A

this produces another type of motile larvae, which escape the snail and perpetrate the skin of a human, entering the bloodstream

34
Q

what are viruses

A

parasite that can only replicate inside a host cell

35
Q

which genetic information do viruses contain

A

viruses contain genetic information in the form of DNA or RNA, packaged in a protective protein coat

36
Q

what are some viruses surrounded by

A

a phospholipid membrane derived form host cell material

37
Q

what does the outer surface of a virus contain

A

antigens that a host cell may or may not be able to detect as foreign

38
Q

what is the first stage of the viral life cycle

A

infection of a host cell with genetic material

39
Q

what is the second stage of the viral life cycle

A

host cell enzymes replicate viral genome

40
Q

what is the third stage of the viral life cycle

A

transcription of viral proteins

41
Q

what is the fourth stage of the viral life cycle

A

assembly and release of new viral particles

42
Q

what are retroviruses

A

a virus that contains RNA as its nucleic acid

43
Q

which enzyme does RNA retrovirus use to form DNA

A

reverse transcriptase which is then inserted into the genome of the host cell

44
Q

viral genes can be expressed to form…

A

viral particles

45
Q

what is transmission

A

the spread of a parasite to a host

46
Q

what is virulence

A

the harm caused to a host species by a parasite

47
Q

how are ectoparasites transmitted

A

through direct contact or by consumption of intermediate hosts

48
Q

how are endoparasites of the body tissues often transmitted

A

by vectors

49
Q

name factors which increase transmission rate

A

the overcrowding of hosts when they are at high density
mechanisms, such as vectors and waterborne dispersal stages, that allow the parasite to spread even if infected hosts are incapacitated

50
Q

what is extended phenotype

A

a theory whereby the parasite modifies the host’s behaviour to increase its own transmission

51
Q

what does the parasite modify in the host’s behaviour

A

alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour

52
Q

parasites often suppress the host immune system and modify….

A

host size and reproductive rate in ways that benefit the parasite growth, reproduction or transmission

53
Q

types of immune response in mammals

A

specific

non-specific

54
Q

what are non-specific defences

A

immune system defence mechanisms in organisms that attempt to prevent any parasites from infecting the potential host

55
Q

examples of non-specific defences

A

physical barriers and chemical secretions
inflammatory response
phagocytes
natural killer cells destroying cells infected with viruses

56
Q

what are physical barriers and chemical secretions in non-specific defences

A

epithelial tissue blocks the entry of parasites
hydrolytic enzymes in mucus
saliva and tears destroy bacterial cell walls
low pH environments of the secretions of stomach
vagina and sweat glands denatures cellular proteins of pathogens

57
Q

what is the inflammatory response in non-specific defences

A

injured cells release signalling molecules
this results in enhanced blood flowing to the site, bringing antimicrobial a theory whereby the parasite modifies the host’s behaviour to increase its own transmission proteins and phagocytes

58
Q

what is phagocytes in non-specific defences

A

killing of parasites using powerful enzymes contained in lysosomes, by engulfing them ad storing them inside a vacuole in the process of phagocytosis

59
Q

what is phagocytosis

A

non-specific defence where phagocytes engulf foreign antigens and digest them using digestive enzymes present in lysosomes

60
Q

what is the first step of phagocytosis

A

phagocyte is attracted to chemical signals produced by a bacterium

61
Q

what is the second step of phagocytosis

A

vacuole forms around the bacterium

lysosomes move towards and fuse with the vacuole

62
Q

what is the third step of phagocytosis

A

lysosomes release digestive enzymes into the vacuole, the bacterium is broken down by enzymes

63
Q

what is the fourth step of phagocytosis

A

vacuole disintegrates releasing digested products into the cytoplasm digested products into the cytoplasm of the phagocyte

64
Q

what is natural kills cells destroying cells infected with viruses

A

these cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis

65
Q

what are natural killer cells

A

lymphocytes responsible for destroying abnormal cells

66
Q

what is apoptosis

A

cell death

67
Q

example of specific cellular defences

A

a range of white blood cells constantly circulate, monitoring the tissue
it is soecific because teh immune system targets specific antigens on the surface of parasites

68
Q

what is an antigen

A

a protein that may induce an immune response if it is foreign

69
Q

what happens if tissue become damaged or invaded

A

cells release cytokines that increase blood flow resulting in non-specific and specific white blood cells accumulating at the site of infection or tissue damage

70
Q

mammals contain many different lymphocytes…

A

each possess a receptor on its surface, which can potentially recognise a parasite antigen

71
Q

what does the binding of an antigen to a lymphocyte receptor do

A

selects that lymphocyte to then divide and produce a clonal population of this lymphocyte

72
Q

what do lymphocytes do

A

some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells

73
Q

what do antibodies have that vary

A

antibodies possess regions where the amino acid sequence varies greatly between different antibodies

74
Q

what does the variable variable region of an antibody give

A

the antibody’s specificity for binding to antigens

75
Q

name the parts of an antigen

A

antigen binding site
variable region
constant region

76
Q

how is the antigen-antibody complex formed

A

when the antigen binds to the antigen binding site

77
Q

what does the formation of the antigen-antibody complex result in

A

inactivation of the parasite, rendering it susceptible to a phagocyte of can stimulate a response that results in cell lysis

78
Q

what does initial antigen exposure produce

A

memory lymphocyte cells specific for that antigen that can produce a secondary response when the same antigen enters the body in the future
when this occurs, antibody production is enhanced in terms of speed of production concentration in blood and duration

79
Q

what are memory lymphocyte cells

A

cloned lymphocytes that remain in the body to respond faster if the individual is exposed to the same antigen a second time

80
Q

what have parasites evolved

A

ways of evading the immune system

81
Q

why do endoparasites mimic host antigens

A

to evade detection and modify host immune response to reduce their chances of destruction

82
Q

what does antigenic variation allow

A

in some parasites, allows them to change between different antigens during the course of infection of a host

83
Q

what is antigenic variation

A

where parasites show great variety amongst different strains

84
Q

what is epidemiology

A

the study of the outbreak and spread of infectious diseases

85
Q

what is herd immunity

A

the resistance to the spread of a contagious disease that results if a sufficiently high proportion of individuals are immune to the disease

86
Q

what is the herd immunity threshold

A

the density of resistant hosts in the population required to prevent an epidemic

87
Q

what do vaccines contain

A

antigens that will elicit an immune response

88
Q

what does similarities between host and parasite metabolism result in

A

difficulty in finding drug compounds that only target the parasite

89
Q

what has to be reflected in the design of vaccines

A

antigenic variation

90
Q

what does parasites being difficult to culture in the lab result in

A

makes it difficult to design vaccines

91
Q

where do challenges arise

A

where parasites spread most rapidly as a result of overcrowding or tropical climates

92
Q

where does overcrowding happen

A

in refugee camps that result from war of natural disaster or rapidly growing cities in LEDCs

93
Q

what does overcrowding result in in terms of treatment

A

make co-ordinated treatment and control programs difficult to achieve

94
Q

what is civil engineering

A

a profession that is involved in the design and manufacture of infrastructure to improve standards of living

95
Q

what is often the only practical control strategy

A

civil engineering projects to improve sanitation combined with co-ordinated vector control

96
Q

what does improvements in parasite control reduce

A

child mortality and results in population-wide improvements in child development and intelligence, as individuals have more resources for growth and development