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Advanced Higher Biology > Unit 2 - Parasitism > Flashcards

Unit 2 - Parasitism Flashcards

(72 cards)

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1
Q

What is an ecological niche?

A

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

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2
Q

What is a species’ fundamental niche?

A

The niche that is occupied in the absence of interspecific competition

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3
Q

What is a species’ realised niche?

A

The niche occupied in response to interspecific competition

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4
Q

What can happen as a result of interspecific competition?

A

Competitive exclusion can occur, where the niches of two species are so similar that one species decline to local extinction

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5
Q

What is the competitive exclusion principle?

A

Two species cannot co-exist in an area permanently if their niches are identical

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6
Q

When can potential competitors co-exist and how?

A

When the realised niches are sufficiently different. They do this by resource partitioning

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7
Q

What is parasitism?

A

A symbiotic relationship between a parasite and its host

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8
Q

Why is parasitism different from predator-prey relationship?

A

The reproductive potential of the parasite is greater than that of the host

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9
Q

What type of niches do parasites have?

A

Narrow/specialised niches

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10
Q

Why do parasites have narrow niches?

A

As they are very host-specific

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11
Q

What happens to parasites as a result of the host providing most of its needs?

A

Many parasites are degenerate, lacking structures and organs found in other organisms

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12
Q

What is an ectoparasite?

A

A parasite which lives on the surface of its host

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13
Q

What is an endoparasite?

A

A parasite which lives within the tissues of its host

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14
Q

What is a definitive host?

A

The host on or in which the host reaches sexual maturity

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15
Q

What is an intermediate host?

A

A host which may be needed for the parasite to complete its lifecycle or to increase its numbers quickly

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16
Q

What is a vector?

A

An organism that plays an active role in the transmission of a parasite from one host to another host, it may also be a host itself.

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17
Q

What is malaria caused by?

A

Plasmodium

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18
Q

Cycle of malaria

A
  • Infected mosquito bites human
  • Plasmodium enters bloodstream
  • Asexual reproduction in liver and then in red blood cells
  • Red blood cells burst, gametocytes released into bloodstream
  • Another mosquito bites infected human
  • Gametocytes enter the mosquito, mature into male and female gametes
  • Sexual reproduction occurs
  • Mosquito can infect another human
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19
Q
A
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20
Q

What causes schistosomiasis?

A

Schistosomes

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21
Q

Cycle of schistosomiasis

A
  • Schistosomes reproduce sexually in human intestine
  • Fertilised egg pass out via faeces into water
  • Develop into larvae
  • Larvae infect water snails where asexual reproduction occurs
  • This produces another type of motile larvae which escapes snail and penetrates skin of human and enter bloodstream
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22
Q

What are viruses?

A

Parasites that can only replicate inside a host cell

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23
Q

What do viruses contain?

A

Genetic material in the form of DNA or RNA packaged in a protective protein coat

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24
Q

What are some viruses surrounded by?

A

A phospholipid membrane derived from host cell materials

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25
What does the outer surface of a virus contain?
Antigens that a host cell may or may not be able to detect as foreign
26
Stages of viral life cycle
- Virus approaches host cell - Virus attaches to cell - Viral genetic material injected into host cell - Viral genes interrupts host cell metabolism - Host cell enzymes replicate viral genome - Transcription of viral genes and translation of viral proteins occurs - New viruses are assembled as the new DNA enter new protein coat - New viral particles leave host cell to infect new hosts
27
What are retroviruses?
Viruses that carry RNA instead of DNA
28
How do RNA retroviruses form DNA?
They use enzyme reverse transcriptase
29
What is transmission?
The spread of a parasite to a host
30
What is virulence?
The harm caused to a host species by a parasite
31
How are ectoparasites transmitted?
Through direct contact
32
How are endoparasites transmitted?
By vectors or consumption of intermediate hosts
33
Factors that increase transmission rates
- Overcrowding of hosts when they are at a high density - Mechanisms, such as vectors and waterborne dispersal stages, that allow the parasite to spread even if infected hosts are incapacitated
34
35
Why is host behaviour exploited and modified by parasites?
To maximise transmission
36
What types of host behaviour is altered?
- Foraging - Movement - Sexual behaviour - Habitat choice - Anti-predator behaviour
37
What does the host behaviour become part of?
The extended phenotype of the parasite
38
Aspects of immune response in mammals
Specific and non-specific
39
What are non-specific defence mechanisms?
Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells destroying cells infected with viruses
40
How does the skin act as a non specific defence?
Epithelial tissue forms a physical barrier which blocks entry of parasites
41
How do hydrolytic enzymes act as non-specific defences?
Hydrolytic enzymes in mucus, saliva and tears destroy bacterial cell walls
42
How do acid secretions act as non-specific defences?
Acid secretions in the stomach, vagina and sweat glands gives a low pH environment which denatures cellular proteins of many pathogens
43
How do injured cells act as non-specific defences?
Injured cells release signalling molecules which causes enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes
44
How do phagocytes act as a non-specific defence?
Phagocytes are white blood cells that engulf invading pathogens and store them inside a vacuole in the process of phagocytosis
45
How do natural killer cells act as non-specific defences?
They identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis
46
How are specific immune responses carried out?
By a range of white blood cells which constantly circulate, monitoring the tissues
47
What happens when tissues 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
48
What are lymphocytes?
They are white blood cells that have a receptor on its surface which can potentially recognise a parasite antigen
49
What happens when an antigen bind to a lymphocyte’s receptor?
It selects that lymphocyte to then divide and produce a clonal population of this lymphocyte
50
What can some lymphocytes produce?
Antibodies
51
What can some lymphocytes induce?
Apoptosis in parasite-infected cells
52
What varies greatly between different antibodies?
Regions of amino acid sequences
53
What does this variable region give the antibody?
Its specificity for binding antigen
54
What happens when the 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
55
What is formed when the antigen binds to the binding site?
Memory lymphocytes cells
56
What can memory lymphocytes do?
They 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
57
Strategies used by parasites to evade the immune system
- Endoparasites mimic host antigens to evade detection and modify host immune response to reduce their chances of destruction - Antigenic variation in some parasites allows them to change between different antigens during the course of infection of a host - Allow reinfection of the same host with the new variant
58
How do some viruses escape immune surveillance?
By integrating their genome into host genomes, existing in an inactive state known as latency
59
When does the virus become active again?
When favourable conditions arise
60
What is epidemiology?
The study of the outbreak and spread of infectious disease
61
What is the herd immunity threshold?
The density of resistant hosts in the population required to prevent an epidemic
62
What do vaccines contain and what do they do?
They contain antigens that will elicit an immune response
63
Why are similarities between host and parasite a challenge when finding treatment?
It makes it difficult to find drug compounds which only target the parasite and not the host
64
Why is the need for host conditions for parasites a challenge when finding treatment?
It means its difficult to culture them in a laboratory and therefore difficult to design vaccines
65
Why is the rapid evolution of antigenic markers in parasites a challenge when finding treatment?
It means that this antigenic variation has to be reflected in the design of vaccines which can lead to people needing to be vaccinated annually e.g. influenza virus
66
Where do parasites spread more rapidly?
In tropical climates and overcrowding
67
Why can overcrowding be a challenge?
It is often in camps of refugees as a result of war or natural disaster which means poor sanitation and shortage of sewage treatment, so ideal conditions for rapid spread of parasites.
68
Why are tropical climates a challenge?
Parasites are more common in tropical climates because large numbers of insect vectors used by parasites for transmission
69
What do these conditions make difficult?
To achieve co-ordinated treatment and control programs
70
What is civil engineering doing as a control method?
Improve sanitation
71
What else is a practical control strategy?
Co-ordinated vector control
72
What is the benefit of improving 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

Advanced Higher Biology (13 decks)

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