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Advanced Higher Biology > 2.5 Parasitism > Flashcards

2.5 Parasitism Flashcards

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1
Q

What is an ecological niche?

A

A multidimensional summary of tolerances and requirements of a species

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2
Q

What are tolerances of a species?

A

The range within which it can survive, these can be biotic or abiotic

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3
Q

What is the fundamental niche?

A

The niche occupied in the absence of any interspecific competition

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4
Q

What is the realised niche?

A

The niche occupied in response to interspecific competition

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5
Q

What is competitive exclusion?

A

Where the realised niches of the two species are very similar and one declines to total extinction, it occurs due to interspecific competition

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6
Q

What is resource partitioning?

A

Where the realised niches of the two species are sufficiently different potential competitors can co-exist by this, it occurs due to interspecific competition

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7
Q

What is a symbiont?

A

An organism that lives in close association with another

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8
Q

What is a parasite?

A

A symbiont which gains benefit in terms of nutrients at the expense of its host

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9
Q

What is a non-symbiotic organism which gains at the expense of others?

A

Predators

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10
Q

What is the reproductive potential of a parasite compared to its host?

A

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

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11
Q

Why is a parasite more energy efficient?

A

It gains nutrients directly from the host, so no foraging takes place

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12
Q

What is the niche of a parasite?

A

Parasites have very narrow niches as they are very host specific

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13
Q

What is a degenerate parasite?

A

Many parasites are degenerate, which means that they are lacking in structures and organs found in other organisms since the host provides so many of the parasites needs

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14
Q

What is an ectoparasite?

A

A parasite whos niche is on the surface of its host

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15
Q

What is an endoparasite?

A

A parasite whos niche is within the body of the host

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16
Q

What is an intermediate host?

A

Organisms on/in which developmental stages happen to complete the parasites life cycle

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17
Q

What is the definitive host?

A

Organism on/in which the parasite which achieve sexual maturity and consequently sexually reproduce

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18
Q

What is a vector?

A

Organism which transmits the parasite and may also be a vector

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19
Q

What is a virus?

A

Parasites which can only replicate inside a host cell

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20
Q

What are key features of viruses?

A

Genetic material can be DNA or RNA,
A phospholipid membrane may surround a virus (derived from host cell materials),
Antigens on the surface of a virus may be detected by a host cell and recognised as being foreign

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21
Q

What is the process of virus replication?

A
  1. Virus attaches itself to surface of the host cell
  2. Virus injects its DNA into host cell
  3. Virus interrupts host cell metabolism, often entering host genome
  4. Virus used host cell machinery and raw materials to replicate DNA
  5. Using host cell resources, DNA is transcribed into mRNA and translated into protein so more viral coats produced
  6. New DNA enters newly formed protein coats, thus producing many more viruses
  7. These then leave the cell to infect new cells and the host cell undergoes lysis, bursting
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22
Q

What is a bacteriophage?

A

A virus that uses a bacterium as a host cell

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23
Q

What are retroviruses?

A

Viruses with RNA rather than DNA e.g. HIV and hepatitis

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24
Q

What happens when a retrovirus injects RNA?

A

The virus also imjects enzyme reverse transcriptase which will form DNA from the RNA. The DNA Is then insterted into the genome of the host cell

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25
What is transmission?
The spread of parasites to hosts
26
What is virulence?
the harm caused to a host by a parasite
27
How are ectoparasites transmitted?
Direct contact is used, or by consumption of intermediate hosts
28
How are endoparasites transmitted?
Vectors are used
29
What can increase transmission rates?
Overcrowding of hosts, means of transition (vectors or waterborne dispersial stages), exploiting natural host behaviours
30
What can parasites do to hosts to maximise transmission?
Modify their behaviour e.g. rabies makes hosts more aggressive so it will bite and pass on virus in saliva
31
What are examples of parasite life cycles?
Plasmodium (causes malaria), Schistosoma (causes schistosomiasis)
32
What are ways that parasites evade the immune system?
Mimic host antigens, Antigenic variation, Integrate genome into host genome
33
How do parasites mimic host antigens?
Produce surface antigens that mimic those of the host, this helps it evade detection and so there is a reduced antibody response
34
How does antigenic variation help parasite evade immune detection?
Parasites have hundreds of copies of surface antigen genes and each new generation expresses a new randomly selected set of these genes. This allows the parasite to evolve quicker than the host immune system can respond and allow re-infection with a new variant
35
How does integrating genome into host genome help parasites evade detection?
They integrate their genomes into host genomes, existing in an inactive state known as latency, the virus becomes active again when favourable conditions arrive
36
What is epidemiology?
The study of the outbreak and spread of infectious disease
37
What is the herd immunity threshold?
The density of resistant hosts required to prevent an epidemic
38
When does herd immunity occur?
When the number of resistant hosts are increased in the population through vaccination
39
What do vaccines allow?
Active immunity to be acquired as the body produces antibodies in response to antigens present in the vaccine
40
What is immunological memory?
White blood cells provide a larger and quicker response if a pathogen with the antigen is encountered, this can be as a result from vaccination
41
What are challenges in vaccine development?
Some parasites are difficult to culture in a lab, Difficult to study the parasite outside the host, Rapid antigen change in parasites
42
Why are parasites difficult to culture in a lab?
Due to their complex life cycles, narrow niche and high host specificity
43
Why is drug development to kill parasites hard?
The metabolism of the host and parasite are very similar, so a drug meaning to kill a parasite may harm the host
44
What are LEDCs?
Less Economically Developed Countries
45
Why dont LEDCs invest in antiparasitic drugs?
Complex and costly nature of development
46
What are some strategies which target transmission stages?
Civil engineering projects to improve sanitation, Coordinated vector control
47
How do civil engineering projects work?
Improve sanitation by installing toilet facilities, sewage systems and water taps from boreholes.
48
What do civil engineering projects prevent?
The mixing of drinking water with water that is contaminated with human waste, blocking the transmission route
49
How may coordinated vector control strategies work?
Spraying houses with insecticides and using bed nets
50
Where do parasites spread most rapidly?
Conditions where coordinated treatment and control programs are most difficult to achieve, for example overcrowded areas and tropical climates
51
What is overcrowding?
Can occur in refugee camps as a result of wars or natural disasters. They have high density and may be difficult to get to with resources to control parasites
52
Why do tropical climates help parasite transmission?
They promote large populations of insect vectors that would need to hibernate during cooler seasons in colder climates
53
What is the relationship between parasite control and child mortality?
As parasite control increases, child mortality decreases
54
How does the body defend attacks?
Non-specific and specific means
55
What do white blood cells provide?
Cellular response to pathogens
56
What are antibodies?
Proteins produced during immune responses
57
What is an infectious disease?
A disease resulting from infection of a host organism by a pathogen
58
What is a pathogen?
A disease causing organism e.g. bacteria, fungi, viruses, parasites
59
What is an antigen?
A protein found on the surface of all cells
60
What is a foreign antigen?
If they do not belong to the host they are considered foreign and trigger an immune response, these can belong to bacteria, viruses, fungi, parasitic worms and cells from transplanted tissues
61
What are first line defences?
Non-specific defences which stop the parasite from entering the body, e.g. physical barriers and chemical secretions
62
What are second line defences?
Non-specific responses which attack parasite for being foreign, e.g. natural killer cells, inflammation, phagocytes
63
What are third line defences?
Specific cellular defences which attack specific antigens on parasite, e.g. lymphocytes, antibodies
64
What are examples of physical barriers of defence?
Nasal hairs and epithelial tissue
65
What are examples of chemical secretions of defence?
Sweat glands, mucus, tears, vagina, saliva, stomach
66
What are the steps of phagocytosis?
1. Phagocytes move to injury site 2. Plasma membrane of the phagocyte engulfs the parasite 3. Parasite is brought into the phagocyte in a vacuole 4. Lysosomes move towards the vacuole 5. Lysosomes fuse with the vacuole releasing digestive enzymes 6. The parasite is digested
67
What are phagocytes?
White blood cells which are able to migrate out from the blood into the tissue fluid which surrounds cells, they check cell surfaces for self-antigens and if these are not found it is digested
68
What are natural killer cells?
Type of white blood cell which can migrate into the tissue fluid. They detect abnormal cell-surface proteins and attach to the cell and release chemicals into the cell and cause apoptosis
69
What are lymphocytes?
White blood cells found mainly in lymph glands, each one has only one type of antigen receptor on its surface and so a different lymphocyte is produced in response to each foreign antigen
70
What is immune surveillance?
Lymphocytes check fluid which passes through lymph glands for antigens
71
When are lymphocyte cells activated?
Only activated to divide if its receptor protein binds to its specific antigen

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