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Advanced Higher Biology > Unit 2 - Parasitism > Flashcards

Unit 2 - Parasitism Flashcards

(65 cards)

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1
Q

What is a ecological niche?

A

An ecological niche is a multi-dimensional
summary of tolerances and requirements of a
species

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2
Q

What is a fundamental niche?

A

A species has a fundamental niche that it
occupies in the absence of any interspecific
competition

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3
Q

What is a realised niche?

A

A realised niche is occupied in response to
interspecific competition

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4
Q

What is competitive exclusion?

A

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

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5
Q

What is resource partitioning?

A

Where the realised niches are sufficiently
different, potential competitors can co-exist
by resource partitioning

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6
Q

What is paratitism?

A

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

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7
Q

What is the difference in the reproductive potential of the host to parasitise?

A

Unlike in a predator–prey relationship, the
reproductive potential of the parasite is
greater than that of the host.

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8
Q

What do parasites have?

A

a narrow (specialised)
niche as they are very host-specific

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9
Q

What does degenerate mean?

A

lacking structures and organs found in other organisms

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10
Q

What does the host provide?

A

As the host provides so many of the
parasite’s needs, many parasites are
degenerate, lacking structures and organs
found in other organisms

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11
Q

What is an ectoparasite?

A

An ectoparasite lives on the surface of its
host,

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12
Q

What is an endoparasite?

A

lives within the tissues of its host

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13
Q

What is the definitive host?

A

The definitive host is the organism on or in
which the parasite reaches sexual maturity.
Intermediate hosts may also be required for
the parasite to complete its life cycle

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14
Q

What is a vector?

A

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

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15
Q

What is the life cycle of Plasmodium?

A
  • An infected mosquito, acting as a vector,
    bites a human.
  • Plasmodium enters the human bloodstream.
  • Asexual reproduction occurs in the liver and then in the red blood cells.
  • When the red blood cells burst gametocytes are released into the bloodstream.
  • 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
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16
Q

What is the life cycle of Schistosomes?

A
  • Schistosomes reproduce sexually in the human intestine.
  • The fertilised eggs pass out via faeces into water where they develop into larvae.
  • The larvae then infect water snails, where asexual reproduction occurs.
  • This produces another type of motile larvae, which escape the snail and penetrate the skin of a human, entering the bloodstream.
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17
Q

What is the definitive host in plasmodium?

A

In the mosquito

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18
Q

What is the intermediate host in plasmodium?

A

Human where asexual reproduction takes place

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19
Q

What is the definitive host of the schistosomes?

A

Human

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20
Q

What is the intermediate host of the schistosomes?

A

Snail

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21
Q

What are viruses?

A

Viruses are parasites that can only replicate
inside a host cell

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22
Q

What do viruses contain?

A

Viruses contain genetic material in the form
of DNA or RNA, packaged in a protective
protein coat

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23
Q

What are viruses surrounded by?

A

Some viruses are surrounded by a
phospholipid membrane derived from host
cell materials

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24
Q

What does the outer surface of a virus contain?

A

The outer surface of a virus contains
antigens that a host cell may or may not be
able to detect as foreign

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25
What is the viral life cycle stages?
- Infection of host cell with genetic material - host cell enzymes replicate viral genome - transcription of viral genes - translation of viral proteins - assembly and release of new viral particles
26
What is RNA retroviruses?
RNA retroviruses use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell
27
What can viral genes do?
Viral genes can then be expressed to form new viral particles
28
What is transmission?
Transmission is the spread of a parasite to a host
29
What is virulence?
Virulence is the harm caused to a host species by a parasite
30
How are ectoparasites transmitted?
through direct contact
31
How are endoparasites transmitted?
Endoparasites of the body tissues are often transmitted by vectors or by consumption of intermediate hosts
32
What are the factors that increase transmission rates?
- 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
33
Why are host behaviours exploited?
exploited and modified by parasites to maximise transmission
34
What does the host behaviour become?
The host behaviour becomes part of the extended phenotype of the parasite
35
How are host behaviours altered?
- host foraging - movement, - sexual behaviour - habitat choice - anti-predator behaviour.
36
What can parasites do to supress the host immune system?
- Modify host size - Modify reproductive rate (benefit the parasite growth, reproduction or transmission)
37
What do defence against pathogens do humans have?
nonspecific and specific aspects
38
What are the non-specific defences?
Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells
39
What are natural killer cells?
natural killer cells destroying cells infected with viruses
40
What does the epithelial tissue do?
Epithelial tissue blocks the entry of parasites;
41
What do chemical secretions do?
- 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.
42
What happens when cells are injured?
Injured cells release signalling molecules. This results in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes.
43
What is the process of phagocytosis?
Killing of parasites using powerful enzymes contained in lysosomes, by engulfing them and storing them inside a vacuole in the process of phagocytosis
44
What do natural killer cells do?
Natural killer cells can identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis.
45
What are the specific defences?
A range of white blood cells constantly circulate, monitoring the tissues
46
What happens if a tissue becomes 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
47
What do different lymphocytes have?
each possessing a receptor on its surface, which can potentially recognise a parasite antigen
48
What happens when an antigen binds to a lymphocytes receptor?
lymphocyte’s receptor selects that lymphocyte to then divide and produce a clonal population of this lymphocyte
49
What are the two types of things lymphocytes can do?
- Some selected lymphocytes will produce antibodies - others can induce apoptosis in parasite-infected cells
50
What do antibodies possess?
regions where the amino acid sequence varies greatly between different antibodies
51
What does the variable region do?
gives the antibody its specificity for binding antigen
52
What happens when an antigen binds to the binding site?
the antigen-antibody complex formed can result in inactivation of the parasite, rendering it susceptible to a phagocyte, or can stimulate a response that results in cell lysis
53
What do memory lymphocyte cells do?
- 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.
54
What do endoparasites do to evade the immune system?
- mimic host antigens to evade detection and modify host immune response to reduce their chances of destruction - It may also allow re-infection of the same host with the new variant
55
How do some viruses escape immune surveillance?
- by integrating their genome into host genomes, - existing in an inactive state known as latency. - The virus becomes active again when favourable conditions arise
56
What is epidemiology?
Epidemiology is the study of the outbreak and spread of infectious disease
57
What is herd immunity threshold?
The herd immunity threshold is the density of resistant hosts in the population required to prevent an epidemic
58
What do vaccines contain?
Vaccines contain antigens that will elicit an immune response
59
What makes it difficult to find drugs that only target the parasite?
The similarities between host and parasite metabolism
60
What must be reflected in vaccines?
Antigenic variation has to be reflected in the design of vaccines
61
Why is it often difficult to design vaccines?
Some parasites are difficult to culture in the laboratory making it difficult to design vaccines
62
What are some of the challenges with parasites spreading?
- overcrowding or tropical climates - Overcrowding can occur in refugee camps that result from war or natural disaster or rapidly growing cities in LEDCs.
63
How do you reduce the rates of transmission?
- Civil engineering projects to improve sanitation combined with co-ordinated vector control may often be the only practical control strategies - Improvements in parasite control reduce child mortality and result in population-wide improvements in child development and intelligence, as individuals have more resources for growth and development
64
What happens when secondary exposure occurs?
When this occurs antibody production is enhanced in terms of speed of production, concentration in blood and duration
65
How are memory cells formed?
Initial antigen exposure produces memory lymphocyte cells specific for that antigen

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