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Advanced Higher Biology 2025 > KA2.5 - Parasitism > Flashcards

KA2.5 - Parasitism Flashcards

Unit 2 (73 cards)

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1
Q

Define an ‘ecological niche’

A

A multi-dimensional summary of a species’ tolerances (e.g., temperature, pH) and requirements (e.g., food, shelter)

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2
Q

Define ‘fundamental niche’

A

Niche occupied in the absence of interspecific competition

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3
Q

Define realised niche

A

Niche occupied in response to interspecific competition

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4
Q

Differentiate between a fundamental niche and a realised niche.

A
  • Fundamental Niche: Occupied in the absence of interspecific competition.
  • Realised Niche: Occupied in response to interspecific competition
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5
Q

What are the two possible outcomes of interspecific competition?

A
  1. Competitive Exclusion
  2. Resource Partitioning
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6
Q

Explain ‘competitive exclusion’

A

Occurs when realised niches are very similar, leading to one species declining to local extinction

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7
Q

Explain ‘resource partitioning’

A

Occurs when realised niches are sufficiently different, allowing competitors to co-exist by dividing resources.

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8
Q

Define ‘parasitism’

A
  • 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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9
Q

Describe how a parasite-host relationship differs from predator-prey in terms of reproductive potential

A

Parasite’s reproductive potential is greater than the host’s

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10
Q

Describe key characteristics of most parasites regarding their niche and physical structure

A
  • Niche: Narrow/specialized (very host-specific)
  • Structure: Often degenerate (lack structures/organs) as the host provides many needs
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11
Q

Name and define the two main classes of parasites

A
  • Ectoparasite: Lives on the surface of its host.
  • Endoparasite: Lives within the host’s body.
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12
Q

How many hosts can parasites require to complete their life cycle?

A

Some require only one; many others require more than one

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13
Q

Define ‘definitive host’

A

The organism on or in which the parasite reaches sexual maturity

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14
Q

Define ‘intermediate host’

A

An organsim which may also be required for the parasite to complete it’s life cycle

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15
Q

Define ‘vector’ in the context of parasites

A

An organism that plays an active role in the transmission of the parasite and may also be a host

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16
Q

What causes malaria and how is it primarily spread?

A
  • Caused by the Plasmodium parasite
  • Spread by infected mosquitoes acting as vectors.
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17
Q

Describe Step 1 of malaria transmission

A

Infected mosquito (vector) bites a human

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18
Q

Describe Step 2 of mosquitto transmission

A

Plasmodium enters bloodstream

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19
Q

Describe Step 3 of mosquitto transmission

A

Asexual reproduction of plasmodium in liver then red blood cells

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20
Q

Describe Step 4 of mosquitto transmission

A

Gametocytes released when red blood cells burst

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21
Q

Describe Step 5 of mosquitto transmission

A
  • Another mosquito bites infected human ingesting gametocyte
  • Gametocyte matures into male and female gametes
  • Sexual reproduction occurs
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22
Q

Describe Step 6 of mosquitto transmission

A

Mosquito can then infect another human host

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23
Q

For Malaria, identify the:

Definitive Host
Intermediate Host
Vector

A

Definitive Host: Mosquito
Intermediate Host: Human
Vector: Mosquito

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24
Q

What causes Schistosomiasis?

A

Schistosomes (parasitic worms)

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25
Describe **Step 1** of schistosomiasis transmission
Schistosomes reproduce sexually in the human intestine.
26
Describe **Step 2** of schistosomiasis transmission
The fertilised eggs pass out via faeces into water and develop into larvae
27
Describe **Step 3** of schistosomiasis transmission
Larvae infect water snails where asexual reproduction occurs
28
Describe **Step 4** of schistosomiasis transmission
This produces another type of motile larvae, which escape the snail and penetrate the skin of a human, entering the bloodstream.
29
For Schistosomiasis, identify the: * Definitive Host * Intermediate Host * Vector
**Definitive Host**: Human **Intermediate Host**: Freshwater Snail **Vector**: Freshwater snails
30
Where do viruses reproduce?
They are parasites that can only replicate inside a host cell
31
Describe the basic components of a virus
* Genetic material (DNA or RNA) packaged in a protective protein coat * Some have a phospholipid membrane with antigens (derived from host cell).
32
Explain the advantage to the virus of having a phospholipid membrane with host cell antigens?
Causes the host cell to may or may not be able to detect the virus as foreign
33
Outline the four general steps of a viral life cycle.
1. Infection of host cell with genetic material. 2. Host cell enzymes replicate viral genome. 3. Transcription of viral genes & translation of viral proteins. 4. Assembly and release of new viral particles.
34
How do RNA retroviruses replicate their genetic material?
Using the enzyme reverse transcriptase to form DNA from their RNA genome, which is then inserted into the host cell's genome.
35
Define 'transmission' in context of parasite
The spread of a parasite to a host
36
Define 'virulence' in context of parasite
Harm caused to a host species by a parasite
37
How are ectoparasites typically transmitted?
Generally through direct contact.
38
How are endoparasites (of body tissues) often transmitted?
By vectors or consumption of intermediate hosts
39
What factors can increase the rate of parasite transmission?
* Overcrowding of hosts (high density). * Readily available vector and waterborne dispersal stages. | The 2nd allows for parasite spread even if host is incapacitated
40
What is the concept of the extended phenotype in parasitism?
Host behaviour is exploited and modified by parasites to maximise their own transmission
41
Give examples of host behaviours that parasites can alter
* Foraging * Movement * Sexual behaviour * Habitat choice * Anti-predator behaviour
42
Besides behaviour, how else can parasites modify their host?
* Suppress the host immune system * Modify host size * Modify host reproductive rate
43
What are the two main aspects of the mammalian immune response?
1. Non-specific 1. Specific
44
What is the first line of defence, and what does it involve?
It's a non-specific defence involving physical and chemical barriers
45
Give an example of a physical barrier in the first line of defence.
Epithelial tissue, which blocks entry to pathogens.
46
Give examples of chemical barriers and their action in the first line of defence.
* Hydrolytic enzymes (in mucus, saliva, tears) destroy bacterial cell walls. * Low pH environments (stomach, vagina, sweat) denature pathogen proteins.
47
When is the second line of defence activated, and what initiates it?
* Activated when 1st line of defence is breached * Begins with the inflammatory response
48
Briefly describe the key steps of the inflammatory response.
1. Injured cells release cytokines 2. Enhances blood flow 3. Brings antimicrobial proteins, non-specific (phagocytes and natural killer cells) and specific white blood cells
49
How do phagocytes kill parasites?
They engulf parasites into a vacuole (phagocytosis); lysosomes containing enzymes then bind to the vacuole to destroy the parasite.
50
How do Natural Killer (NK) cells destroy infected cells?
They identify and attach to virus-infected cells (using antigens) and release chemicals that induce apoptosis (cell death).
51
State the type of white blood cell involved in the specific defence to infection?
Lymphocytes
52
Explain how lymphocytes recognise pathogens?
Possess a surface receptor that can recognise a specific parasite antigen.
53
What happens after an antigen binds to a lymphocyte's receptor?
That lymphocyte is selected to divide, producing a clonal population. Some produce antibodies, others induce apoptosis in infected cells.
54
What are antibodies?
* Proteins that protect you when an unwanted substance enters your body. * Made by lymphocytes in response to binding to an unknown antigen.
55
Explain how antibodies are specific to a particular antigen?
Antibodies possess regions where the amino acid sequence varies greatly between different antibodies. This variable region gives the antibody its specificity for binding antigen.
56
What are the possible outcomes when an antigen-antibody complex forms?
* Inactivation of the parasite (making it susceptible to phagocytes). * Stimulation of a response that results in cell lysis.
57
Describe the purpose of a memory lymphocyte?
They can produce a secondary response when the same antigen enters the body in the future.
58
Explain how a secondary immune response differs from the primary?
Faster, higher concentration and longer duration of antibody production
59
What are the three main methods parasites have evolved to evade the host immune system?
1. Mimicking Host Cells 2. Antigenic Variation 3. Viral Latency
60
How do some parasites use "mimicking host cells" to evade detection?
Endoparasites mimic host antigens to avoid immune detection and modify the host immune response.
61
Explain 'antigenic variation' as a parasite's immune evasion strategy.
Parasites change their surface antigens during infection, allowing re-infection of the same host | (e.g. seasonal flu)
62
Explain Viral Latency as an immune evasion strategy.
Viruses integrate their genome into the host genome, remaining inactive and undetectable by the immune system until favourable conditions cause reactivation.
63
Define 'epidemiology'
The study of the outbreak and spread of infectious disease.
64
What is 'herd immunity'?
Enough people being immune to a disease that the infection can't spread from one person to another
65
What is the herd immunity threshold?
The density of resistant hosts required to prevent an epidemic
66
How can the herd immunity threshold be achieved?
By increasing resistant individuals through vaccination (vaccines contain antigens that elicit an immune response)
67
What is one major challenge in designing drugs that target parasites?
Similarities between host and parasite metabolism make it hard to find drugs that only target the parasite.
68
Why is it difficult to design some vaccines in the laboratory?
Some parasites are difficult to culture in the laboratory
69
How does antigenic variation pose a challenge for vaccine design?
Rapid antigenic variation in some parasites means vaccines need to be constantly adapted to new variants.
70
How does overcrowding complicate the control of parasite spread?
High density of people (e.g., in refugee camps, rapidly growing cities) greatly increases parasite transmission.
71
What climate condition makes coordinated parasite treatment and control difficult?
Tropical climates.
72
What practical strategies are often necessary for parasite control when coordinated treatment is difficult?
* Civil engineering projects to improve sanitation * Coordinated vector control
73
What are the population-wide benefits of effective parasite control?
Reduced child mortality and population-wide improvements in child development and intelligence (due to more resources for growth)

Advanced Higher Biology 2025 (19 decks)

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