2.5 Parasitism Flashcards
(96 cards)
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
what is the second step in the malaria life cycle
Plasmodium enters the human bloodstream
26
what is the third step in the malaria life cycle
asexual reproduction occurs in the liver and then in the red blood cells
27
what is the fourth step in the malaria life cycle
when the red blood cells burst gametocytes are released into the bloodstream
28
what is the fifth step in the malaria life cycle
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
what is the human disease schistosomiasis caused by
schistosomes
30
what is the first step in the schistosomiasis life cycle
schostosomes reproduce sexually in the human intestine
31
what is the second step in the schistosomiasis life cycle
the fertilised eggs pass out via faeces into water where they develop into larvae
32
what is the third step in the schistosomiasis life cycle
the larvae then infect water snails where asexual reproduction occurs
33
what is the fourth step in the schistosomiasis life cycle
this produces another type of motile larvae, which escape the snail and perpetrate the skin of a human, entering the bloodstream
34
what are viruses
parasite that can only replicate inside a host cell
35
which genetic information do viruses contain
viruses contain genetic information in the form of DNA or RNA, packaged in a protective protein coat
36
what are some viruses surrounded by
a phospholipid membrane derived form host cell material
37
what does the outer surface of a virus contain
antigens that a host cell may or may not be able to detect as foreign
38
what is the first stage of the viral life cycle
infection of a host cell with genetic material
39
what is the second stage of the viral life cycle
host cell enzymes replicate viral genome
40
what is the third stage of the viral life cycle
transcription of viral proteins
41
what is the fourth stage of the viral life cycle
assembly and release of new viral particles
42
what are retroviruses
a virus that contains RNA as its nucleic acid
43
which enzyme does RNA retrovirus use to form DNA
reverse transcriptase which is then inserted into the genome of the host cell
44
viral genes can be expressed to form...
viral particles
45
what is transmission
the spread of a parasite to a host
46
what is virulence
the harm caused to a host species by a parasite
47
how are ectoparasites transmitted
through direct contact or by consumption of intermediate hosts
48
how are endoparasites of the body tissues often transmitted
by vectors
49
name factors which increase transmission rate
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
what is extended phenotype
a theory whereby the parasite modifies the host's behaviour to increase its own transmission
51
what does the parasite modify in the host's behaviour
alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour
52
parasites often suppress the host immune system and modify....
host size and reproductive rate in ways that benefit the parasite growth, reproduction or transmission
53
types of immune response in mammals
specific
| non-specific
54
what are non-specific defences
immune system defence mechanisms in organisms that attempt to prevent any parasites from infecting the potential host
55
examples of non-specific defences
physical barriers and chemical secretions
inflammatory response
phagocytes
natural killer cells destroying cells infected with viruses
56
what are physical barriers and chemical secretions in non-specific defences
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
what is the inflammatory response in non-specific defences
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
what is phagocytes in non-specific defences
killing of parasites using powerful enzymes contained in lysosomes, by engulfing them ad storing them inside a vacuole in the process of phagocytosis
59
what is phagocytosis
non-specific defence where phagocytes engulf foreign antigens and digest them using digestive enzymes present in lysosomes
60
what is the first step of phagocytosis
phagocyte is attracted to chemical signals produced by a bacterium
61
what is the second step of phagocytosis
vacuole forms around the bacterium
| lysosomes move towards and fuse with the vacuole
62
what is the third step of phagocytosis
lysosomes release digestive enzymes into the vacuole, the bacterium is broken down by enzymes
63
what is the fourth step of phagocytosis
vacuole disintegrates releasing digested products into the cytoplasm digested products into the cytoplasm of the phagocyte
64
what is natural kills cells destroying cells infected with viruses
these cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis
65
what are natural killer cells
lymphocytes responsible for destroying abnormal cells
66
what is apoptosis
cell death
67
example of specific cellular defences
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
what is an antigen
a protein that may induce an immune response if it is foreign
69
what happens if tissue become damaged or invaded
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
mammals contain many different lymphocytes...
each possess a receptor on its surface, which can potentially recognise a parasite antigen
71
what does the binding of an antigen to a lymphocyte receptor do
selects that lymphocyte to then divide and produce a clonal population of this lymphocyte
72
what do lymphocytes do
some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells
73
what do antibodies have that vary
antibodies possess regions where the amino acid sequence varies greatly between different antibodies
74
what does the variable variable region of an antibody give
the antibody's specificity for binding to antigens
75
name the parts of an antigen
antigen binding site
variable region
constant region
76
how is the antigen-antibody complex formed
when the antigen binds to the antigen binding site
77
what does the formation of the antigen-antibody complex result in
inactivation of the parasite, rendering it susceptible to a phagocyte of can stimulate a response that results in cell lysis
78
what does initial antigen exposure produce
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
what are memory lymphocyte cells
cloned lymphocytes that remain in the body to respond faster if the individual is exposed to the same antigen a second time
80
what have parasites evolved
ways of evading the immune system
81
why do endoparasites mimic host antigens
to evade detection and modify host immune response to reduce their chances of destruction
82
what does antigenic variation allow
in some parasites, allows them to change between different antigens during the course of infection of a host
83
what is antigenic variation
where parasites show great variety amongst different strains
84
what is epidemiology
the study of the outbreak and spread of infectious diseases
85
what is herd immunity
the resistance to the spread of a contagious disease that results if a sufficiently high proportion of individuals are immune to the disease
86
what is the herd immunity threshold
the density of resistant hosts in the population required to prevent an epidemic
87
what do vaccines contain
antigens that will elicit an immune response
88
what does similarities between host and parasite metabolism result in
difficulty in finding drug compounds that only target the parasite
89
what has to be reflected in the design of vaccines
antigenic variation
90
what does parasites being difficult to culture in the lab result in
makes it difficult to design vaccines
91
where do challenges arise
where parasites spread most rapidly as a result of overcrowding or tropical climates
92
where does overcrowding happen
in refugee camps that result from war of natural disaster or rapidly growing cities in LEDCs
93
what does overcrowding result in in terms of treatment
make co-ordinated treatment and control programs difficult to achieve
94
what is civil engineering
a profession that is involved in the design and manufacture of infrastructure to improve standards of living
95
what is often the only practical control strategy
civil engineering projects to improve sanitation combined with co-ordinated vector control
96
what does improvements in parasite control reduce
child mortality and results in population-wide improvements in child development and intelligence, as individuals have more resources for growth and development
