Basics

Question 1

List the types of symbiosis explaining each [4]

Answer 1

Parasitism (parasite benefits at expense of host’s well being)
commensalism (commensalist benefits with no effect on host)
mutualism (both host and mutualist benefit)
phoresis (no metabolic interaction)

Question 2

List the types of parasites explaining each [6]

Answer 2

Mnemonic: FEPOSI
Facultative - not completely dependent on parasitic way of life
Erratic - wanders into another organ normally not found in, but is inside its natural host
Pathogenic - disease causing
Obligatory- completely dependent on host
Sporradic - visits intermittently only when in need
Incidental - accidentally wanders into unnatural host

Question 3

Differences between nematodes and platyhelminths 5]

Answer 3

1. Sexual differentiation (Platyhelminths are mostly hermaphrodites while nematodes are doiecious or sexually differentiated)
2. Presence of suckers (platyhelminths have suckers nematodes don’t)
3. Presence of body cavity (platyhelminths don’t have but nematodes do)
4. Development of alimentary canal (well developed in nematodes, but rudimentary in platyhelminths)
5. Appearance (platyhelminths appear flattened while nematodes appear round and cylindrical)

Question 4

Layers of nematodes going from outside in [4]

Answer 4

Cuticle
Hypodermis
Pseudocoelem
Triradiate gut

Question 5

Name the most favored parasitic microenvironment

Answer 5

GIT system

Question 6

S Mansoni’s ideal microenvironment is…?

Answer 6

circulatory system

Question 7

What the 3 phases of parasitism?

Answer 7

Host-symbiont contact (release of proteolytic enzymes)
Symbiont establishment
Symbiont exit

Question 8

Difference between a reservoir and a vector?

Answer 8

Vector - active source of infection

Reservoir - may or may not be infectious depending on stage the pathogen is in

Question 9

What factors does symbiont establisment require to be successful? [4]

Answer 9

1. Successful habitat selection
2. overcoming host defense mechanisms
3. adequate nourishment
4. stimuli for growth and development

Question 10

Difference between active and passive host-symbiont contact.

Answer 10

in passive contact - the host’s behavior facilitates entry of the parasite
in active contact - the parasite seeks out the host using chemotaxis