Endoparasites

Question 1

What is parasitism?

Answer 1

An ecological interaction where the parasite derives its nourishment from host, who is harmed.

Question 2

Name the 2 major types of parasites

Answer 2

Endoparasitism
Ectoparasitism

Question 3

Name and define 2 other types of parasites

Answer 3

Parasitoids = one part of life cycle is parasitic- eggs laid on host, larvae develop inside and eat host from inside out
Social parasities = one part of life cycle is parasitic- females lay eggs in nests of same or different species and the host bird of this nest raises offspring

Question 4

What are some features of a parasite?

Answer 4

• smaller than host but have a rapid life cycle- so have a massive impact

Question 5

What proportion of organisms are parasites?

Answer 5

1/3- potentially 1/2 of all species are parasites

Question 6

What are some features of endoparasites?

Answer 6

= live inside host- can be extracellulary or intracellularly
- some of biggest killers on the planet- cause of disease

Question 7

What are some challenges faced by endoparasites?

Answer 7

• Must evade host immune system
• Dispersal to different hosts is difficult as only adapted to live inside of host

Question 8

What are the different types of parasitic hosts + how are they different?

Answer 8

Can be primary (=definitive) or secondary (=intermediate):
- Primary hosts:
long residency stage = parasites reach maturity here and often reproduce sexually
- secondary hosts
parasites stay a short time and often complete a developmental stage then activate exit strategy to primary/tertiary host

Question 9

What are vectors?

Answer 9

Vectors transmit parasites between hosts = solve dispersal issue e.g. mosquitoes

Question 10

What are reservoirs?

Answer 10

= long term hosts receiving little or no damage but cannot eradicate parasite

Question 11

Name some types of intracellular parasites and what do they usually require?

Answer 11

Viruses
Bacteria
Fungi
Protozoa
- usually require vector to disperse

Question 12

Describe the malaria life cycle.

Answer 12

1. Mosquitoes = primary host of malaria as sexual stage is completed within it
2. Mosquito takes up gametocytes and can also inject sporozoites released from oocysts
3. Sporozoites enter secondary host (e.g. human) and go to liver
4. Move out into asexual blood stage = clonal stage
5. = 2 types of gametocytes produced and cycle continues

Question 13

what are gametocytes?

Answer 13

cell that divides to form gametes

Question 14

what are sporozoites?

Answer 14

motile, spore-like stage in life cycle of some parasites- usually infective agent

Question 15

is malaria a successful parasite and why?

Answer 15

Yes- infects almost every group of vertebrates
and is present on every continent apart from Antarctica

Question 16

Describe the life cycle of toxoplasma gondii in cats and their prey

Answer 16

1. Infected mice seeks out cats
2. New cats infected by eating mice- mice = vector
3. New mice infected by eating food contaminated with cat poo or dead animals

Question 17

Define oocysts

Answer 17

a zygote formed from a parastite

Question 18

How is toxoplasma gondii so easily dispersed?

Answer 18

Sporulated oocysts = really tough egg that can survive in the environment for further transmission

Question 19

Name some examples of extracellular parasites

Answer 19

• flatworms = Platyhelminthes
• tapeworms = Cestodes
• flukes = trematodes
• roundworms = nematodes

Question 20

Describe the life-cycle of a tape worm

Answer 20

1. larvae ensist into tissue to produce cysts- where they can emerge later or are consumed by primary host
2. Digestion breaks down the cyst and can infect
3. egg phase can end up in faeces which can result in transmission of eggs to secondary host

Question 21

Are parasites morphologically complex and why?

Answer 21

There has been some loss of morphological complexity- no need for eyes, gut etc
- But there is a need for specialisation in different sensory receptors due to challenges

Question 22

Describe the life-cycle of lyme disease

Answer 22

1. relies on ticks as reservoirs and vectors- as they are small so are better for replication but do not move fast so new host required
2. Ticks require 3 hosts to complete life cycle

Question 23

What dies the cordyceps fungus do?

Answer 23

1. Take over ants and force them to climb vertically up trees
2. Before ant dies it is forced to bite down on vegetation
3. Fruiting bodies burst and releases spores onto forest floor infecting more ants

Question 24

why do mice seek out cats when infected with toxoplasma gondii?

Answer 24

Reduces mice fear of natural predators:
1. Forms cysts in brain which may increase dopamine production associated with the smell of cat urine

Question 25

What % of humans and cats are infected with toxoplasma gondii?

Answer 25

cats = 40%
humans = 33%

Question 26

What has been observed in humans when infected with toxoplasma gondii?

Answer 26

Increased risk taking- only correlation

Question 27

What are gordian worms and what do they infect?

Answer 27

very long worm with 350 species belonging to the Nematomorpha phylum
- infect insects and crustaceans

Question 28

How do gordian worms affect hosts?

Answer 28

1. Stops any noise to prevent predators
2. Non-aquatic hosts is forced to enter water
3. Burrows out of body and lays eggs
4. larvae infects secondary host

Question 29

Define: immunomodulation

Answer 29

= controlling of the immune reponse

Question 30

why do parasites use immunomodulation?

Answer 30

1. reduce immune reponse to prevent worm being outed
2. Host immune reactions reduces over time with length of residency of parasite to allow for long-term survival for reproduction and dispersal

Question 31

What does the hygiene hypothesis suggest and where is the evidence for this?

Answer 31

Lack of parasties leads to a dysregulated immune system- as parasitites carry out immunomodulation to prevent overactivity

Increased prevalence in Western countries of allergies and diseases

Question 31

What does the hygiene hypothesis suggest and where is the evidence for this?

Answer 31

Lack of parasties leads to a dysregulated immune system- as parasitites carry out immunomodulation to prevent overactivity

Increased prevalence in Western countries of allergies and diseases