Parasitism

Question 1

What is an ecological niche

Answer 1

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

Question 2

What is a fundamental niche

Answer 2

A niche a species occupies in the absence of any interspecific competition

Question 3

What is a realised niche

Answer 3

A niche in response to interspecific competition

Question 4

What is competitive exclusion

Answer 4

The niches of two species are so similar that one declines to local extinciton

Question 5

What is resource partitioning

Answer 5

When potential competitors co-exist since realised niches are sufficiently different

Question 6

What type of interaction is parasitism

Answer 6

Symbiotic (+/-)

Question 7

Does the parasite or the host have a greater reproductive potential

Answer 7

The parasite does

Question 8

What kind of niche does a parasite have

Answer 8

A very narrow, specialised host specific niche

Question 9

What makes parasites degenerate

Answer 9

The way the host provides so many of the parasite’s needs that it lacks in structures and organs found in other organisms

Question 10

Where does an ectoparasite live

Answer 10

On the surface of its host

Question 11

Where does an endoparasite live

Answer 11

In the tissue of its host

Question 12

What is the definitive host

Answer 12

The organism on or in which the parasite reaches sexual maturity

Question 13

What is a vector

Answer 13

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

Question 14

Explain the transmission of the disease malaria

Answer 14

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 blood cells
Blood cells burst releasing gametocytes into bloodstream
Another mosquito bites an infected human and gametocytes enter the mosquito, maturing into males and female gametes, allowing sexual reproduction to now occur.
The mosquito can then infect another human host.

Question 15

Explain the transmission of schistosomiasis

Answer 15

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.

Question 16

What are viruses

Answer 16

Parasites that can only replicate inside a host cell

Question 17

What do viruses contain

Answer 17

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

Question 18

What are some viruses surrounded in

Answer 18

A phospholipid bilayer derived from host cell materials

Question 19

What allows viruses to be detected by host cells

Answer 19

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

Question 20

Describe the viral life cycle stages

Answer 20

Infection of host cell with genetic material
Host cell enzymes replicate the viral genome
Transcription of viral genes and translation of viral proteins
Assembly and release of new viral particles

Question 21

What enzyme do RNA retroviruses use

Answer 21

Reverse transcriptase to form DNA

Question 22

What happens to the DNA once it has been converted

Answer 22

It is inserted into the genome of the host cell which forms new viral particles

Question 23

What is transmission

Answer 23

The spread of a parasite to a host

Question 24

What is virulence

Answer 24

The harm caused to a host species by a parasite

Question 25

How are ectoparasites transmitted

Answer 25

Via contact

Question 26

How are endoparasites transmitted

Answer 26

By vectors or by consumption by intermediate hosts

Question 27

Name 2 factors that increase transmission rates

Answer 27

Overcrowding of hosts when at high density Mechanisms such as vectors and waterborne dispersal stages, that allow the parasite to spread even if infected hosts are incapacititated

Question 28

How do parasites maximise transmission

Answer 28

They exploit and modify hosts to max transmission

Question 29

Name 5 examples of when host behaviour is exploited

Answer 29

``` Alteration of host foraging Sexual behaviour Habitat choice Anti-predator behaviour Movement ```

Question 30

What becomes part of the extended phenotype of a parasite

Answer 30

The host's behaviour

Question 31

How can parasites increase their own growth, reproduction and transmission

Answer 31

By suppressing the host immune system and modify host size and reproductive rate

Question 32

Give 4 examples of non-specific defences

Answer 32

``` physical barriers chemical secretions inflammatory response phagocytes NK cells destroying cells ```

Question 33

What does epithelial tissue do in terms of defence

Answer 33

blocks the entry of parasites

Question 34

What does hydrolytic enzymes in mucus, saliva and tears do

Answer 34

Destroy cell walls

Question 35

What does low pH of stomach, vagina and sweat glands do

Answer 35

dentures cellular proteins of pathogens

Question 36

Explain inflammatory response

Answer 36

Injured cells releasing signalling molecules (cytokines), resulting in enhanced blood flow to the site, bringing antimicrobial proteins and phagocytes (specific and non-specific white blood cells)

Question 37

Explain phagocytosis

Answer 37

The killing of parasites using powerful enzymes contained in the lysosome, by engulfing them and storing them inside a vacuole in the process of phagocytosis

Question 38

Describe how NK cells work

Answer 38

They identify and attach to cells infected with viruses, releasing chemicals that lead to cell death by inducing apoptosis

Question 39

What makes a lymphocyte specific to a parasitic antigen

Answer 39

The receptor

Question 40

What happens upon binding of a lymphocyte to the antigen of a parasite

Answer 40

The lymphocyte divides and produces a clonal population of lymphocytes

Question 41

What are the 2 possible roles of lymphocytes

Answer 41

Some will produce antibodies and others will induce apoptosis in parasite -infected cells

Question 42

What gives each antibody its specificity for the binding antigen

Answer 42

The variation in amino acid sequence in particular regions

Question 43

What is the effect of antibody binding

Answer 43

Inactivation of the parasite, rendering it susceptible to a parasite Stimulating a response that results in cell lysis (breaking down of a cell membrane)

Question 44

What is the use of memory cells

Answer 44

When the same antigen enters the body in future a secondary response is produced The secondary response is enhanced in terms of speed of production, concentration in blood and duration

Question 45

How do endoparasites evade detection

Answer 45

They mimic host antigens

Question 46

How do endoparasites reduce their chances of destruction

Answer 46

They modify host immune response

Question 47

What is antigenic variation in terms of parasites

Answer 47

It is when parasites change between different antigens during the course of infection of a host

Question 48

What is the cause of reinfection of the same host by a parasite

Answer 48

antigenic variation

Question 49

How can viruses escape immune surveillance

Answer 49

By integrating their genome into host genomes, existing in an inactive state known as latency. The virus then becomes active again when favourable conditions arise

Question 50

What is epidemiology

Answer 50

The study of the outbreak and spread of an infectious disease

Question 51

What is the herd immunity threshold

Answer 51

The density of resistant hosts in the population required to prevent an epidemic

Question 52

How do vaccines work

Answer 52

They contain antigens that will elicit an immune response

Question 53

What makes it difficult to find drug compounds that only target the parasite

Answer 53

The similarities between host and parasite metabolism

Question 54

What are 2 considerations when designing vaccines

Answer 54

Antigenic variation | Some parasites are difficult to culture in the lab