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

The niche a species occupies in absence of any interspecific competition,

Question 3

What is a realised niche?

Answer 3

Occupied in response to interspecific competition

Question 4

What can happen as a result of interspecific competition?

Answer 4

Competitive exclusion can occur

Question 5

When does competitive exclusion occur?

Answer 5

Where the niches of 2 species are so similar that one declines to local extinction

Question 6

What can happen when realised niches are sufficiently different?

Answer 6

potential competitors can co-exist by resource partitioning

Question 7

Parasitism is a ___________ relationship

Answer 7

symbiotic

Question 8

How do parasite-host and predator-prey relationships differ?

Answer 8

Unlike in predator-prey relationships, the reproductive potential of the parasite is greater than that of the host

Question 9

Why do most parasites have a narrow (specialised) niche?

Answer 9

because they are very host-specific

Question 10

Why are many parasites degenerate?

Answer 10

Because the host provides so many of the parasite’s needs

Question 11

What does degenerate mean?

Answer 11

lacking structures and organs found in other organisms

Question 12

What is an ectoparasite?

Answer 12

Lives on the surface of its host

Question 13

What is an endoparasite?

Answer 13

Lives within the tissues of its host

Question 14

What is a vector?

Answer 14

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

Question 15

What causes the human disease Malaria?

Answer 15

Plasmodium

Question 16

What causes the human disease schistosomiasis?

Answer 16

Schistosomes

Question 17

What are viruses?

Answer 17

Viruses are parasites that can only replicate inside a host cell

Question 18

Some viruses are surrounded by a

Answer 18

phospholipid membrane derived from host cell material

Question 19

What do viruses contain?

Answer 19

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

Question 20

What does the outer surface of a virus contain?

Answer 20

antigens that a host cell may or may not be able to detect as foreign

Question 21

What is the importance of the enzyme reverse transcriptase?

Answer 21

RNA retroviruses use the enzyme reverse transcriptase to form DNA, which is then inserted into the genome of the host cell. Viral genes can then be expressed to form new viral particles

Question 22

What is the definitive host?

Answer 22

The organism in which the parasite reaches sexual maturity

Question 23

What is the intermediate host?

Answer 23

May also be required for the parasite to complete its life cycle

Question 24

What is transmission?

Answer 24

The spread of a parasite to a host

Question 25

What is virulence?

Answer 25

The harm caused to a host species by a parasite

Question 26

How are ectoparasites generally transmitted?

Answer 26

Through direct contact

Question 27

How are endoparasites generally transmitted?

Answer 27

By vectors or by consumption of intermediate hosts

Question 28

Factors that increase transmission rates?

Answer 28

*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

Question 29

Examples of how host behaviour exploited and modified by parasites to maximise transmission?

Answer 29

Alteration of host foraging, movement, sexual behaviour, habitat choice or anti-predator behaviour.

Question 30

How do parasites modify the host's behaviour in ways that benefit the parasite growth, reproduction or transmission?

Answer 30

Parasites often suppress the host immune system and modify host size and reproductive rate

Question 31

Non-specific immune defences

Answer 31

Physical barriers, chemical secretions, inflammatory response, phagocytes, and natural killer cells destroying cells infected with viruses

Question 32

What do epithelial tissue do?

Answer 32

blocks the entry of parasites;

Question 33

hydrolytic enzymes in mucus, saliva and tears...

Answer 33

destroy bacterial cell walls

Question 34

low pH environments of the secretions of stomach, vagina and sweat glands...

Answer 34

denatures cellular proteins of pathogens.

Question 35

Specific cellular defences

Answer 35

A range of white blood cells constantly circulates, monitoring the tissues

Question 36

What happens if tissues become damaged or invaded?

Answer 36

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

Question 37

What does binding of an antigen to a lymphocyte’s receptor do?

Answer 37

selects that lymphocyte to then divide and produce a clonal population of this lymphocyte

Question 38

Different types of lymphocytes

Answer 38

Some selected lymphocytes will produce antibodies, others can induce apoptosis in parasite-infected cells

Question 39

Antibodies possess regions where the amino acid

Answer 39

sequence varies greatly between different antibodies. This variable region gives the antibody its specificity for binding antigen

Question 40

Endoparasites mimic host antigens to

Answer 40

evade detection and modify host immune response: to reduce their chances of destruction

Question 41

Antigenic variation in some parasites allows them to

Answer 41

change between different antigens during the course of infection of a host It may also allow re-infection of the same host with the new variant

Question 42

Some viruses escape immune surveillance by

Answer 42

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

Question 43

What is epidemiology?

Answer 43

the study of the outbreak and spread of infectious disease

Question 44

What is the herd immunity threshold?

Answer 44

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

Question 45

Vaccines contain

Answer 45

antigens that will elicit an immune response

Question 46

Drug designing difficulties?

Answer 46

The similarities between host and parasite metabolism makes it difficult to find drug compounds that only target the parasite Antigenic variation has to be reflected in the design of vaccines Some parasites are difficult to culture in the laboratory making it difficult to design vaccines

Question 47

What may be the only practical control strategies?

Answer 47

Civil engineering projects to improve sanitation combined with co-ordinated vector control

Question 48

Parasites spread rapidly because of

Answer 48

Overcrowding, tropical environments

Question 49

Improvements in parasite control reduce

Answer 49

child mortality and result in population-wide improvements in child development and intelligence, as individuals have more resources for growth and development