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Sem 1: Parasite and pathogen ecology > Week 2 > Flashcards

Week 2 Flashcards

1
Q

What are the 5 key ingredients to a parasitic relationship?

A

Opportunity
Fitness gain
Exposure gain
Pre-adaptation
Intermediary steps

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2
Q

What does opportunity mean?

A

Species needed to have a frequent contact to form any relationship

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3
Q

What are the 4 types of relationships between species?

A

Mutualistic
Commensal
Amensal
Predatory

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4
Q

Is there a general relationship between size and parasitism?

A

For a host/parasite relationship to form a large size difference is generally needed

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5
Q

Name 3 benefits to parasitism?

A

Cheap nutrition
Transport
Shelter

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6
Q

Will evolution between generations select for specalist organs in parasites?

A

Only if there is a fitness benefit

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7
Q

Can parasitism form in all relationships?

A

There must be potential for host explotation from the beginning of the host/parasite relationship

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8
Q

How does parasitism form?

A

Individuals that will become parasitic are those that capable of remaining in or on the host and gain greater fitness benefit then if the were mutalistic

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9
Q

How does exposure time impact chances of parasitism?

A

Species will be only able to become parasites if the close relationship with the host can be maintained over generations

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10
Q

What is pre-adaptation?

A

The evolution of previous traits i.e mouth shape or certain behaviours allow for the easier transitions to parasitism

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11
Q

What is the dauer hypothesis?

A

That the dauer larvae morphology is a pre-adaptation to parasitism

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12
Q

Why is the dauer stage believed to be pre-adaptation to parasitism?

A

Free living nematodes have a dauer L3 larval stage
These have stopped development and are non feeding and highly stress resistant, these are often used as a disperse stage to colinise distant environment
Parasitic nematodes have a larval stage form that dauers which is used to at the dispersal stage

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13
Q

What are facultative parasites?

A

Facultative parasites are organisms that may adopt parasitic activity but aren’t reliant on it

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14
Q

What are obligate parasites?

A

Oligate parasites are organisms that can’t complete their life cycle without exploiting a host

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15
Q

What is the phoretic pathway?

A

Small organisms may attach to the larger ones to aid with dispersal
This can often become more parasitic over time

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16
Q

Why would an orgnanism turn to parasitism to escape hostile environment?

A

As they are better protected and better fed then if they lived in their free living stage

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17
Q

What is copepodes strategy to tough environments?

A

Either Diapause (arrested devlopement) or parasitism of fish

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18
Q

Can a prey species turn into a parasite?

A

Yes they can as seen with the ciliate Lambornella clarki?

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19
Q

What is lambornella clarki’s (ciliate) relationship with parasitism?

A

They are facultative parasite though often found free-living form
In response to water born substances produced by predatory mosquitos the Lambornella clarki form parasitic theronts, these attach and then penetrate the mosquitos cuticle.

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20
Q

How many times are parasitism evolved?

A

An unknown amount of times
In nematodes parasitism has evolved 4 times independantly
Where as acanthocephala it was evolved once

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21
Q

What is sacculinization?

A

The process in which organisms lose sense organs and become simplier

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22
Q

Does sacculinization apply to parasites?

A

Functions such as locomotion and mechanical digestion are taken care of by host, this means selection is in favour of removing them. Though the energy that went into developing and maintaining these resources may allow for other structures to develop eg parasitic platyhelminthes have adaptations for living in anaerobic environments

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23
Q

Is parasitism reversible?

A

Yes and no depending on the dependancy of specialisations

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24
Q

Is parasitism reversible for obligate intracellular parasites?

A

If the parasites have lost functional gene categories then they maybe be irreversibly dependant on parasitism

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25
Name an example of a parasite which could reverse its parasitism?
Diplomonadida are a group of protists, with some are free living and some of which are parasitic - suggesting reversal is possible
26
What is upward incorporation?
First host is the intermidiate host with the final host being a predator of the intermidiate host
27
What is downward incorporation?
First host is the final host with an intermidiate host evolving later
28
What are the outcomes of a parasite if a host goes extinct?
1 - Parasite goes extinct 2 - Parasite finds alternative host 3 - Shorten lifestyle
29
What are the benefits to truncate your lifecycle?
Undergoing developement prematurely in an intermediary host You could use an intermediary host for multiple life stages Truncate life cycle seasonally - seen with the trematode Gymnophallus choledochus with 2 hosts in winter and 3 hosts in summer
30
What is the virus first hypothesis?
Viruses stemmed from pre-cellular life with self repilicating based on RNA - predating the domains of life
31
What is the cell first hypotheses?
Viruses evolved from cells that lost their components and genes becoming obligate parasites
32
What are example of pre-infection host defences?
Barriers - skin Secretions Reducing exposure - not eating rotten food
33
What are examples of post-infection host defence?
Physiological defences - immune system Behavioural defences
34
What are the types strategies for post-infection host defences?
Resistance - clear a pathogen at first sight Tolerance - allowing pathogens to happen but manage the number of pathogens
35
What are the pros and cons of the resistance strategy?
Pros - removes parasites so on an individual level no loss in fitness Cons - can be a reduction on a community level for fitness and parasites will evolve to counteract this due to the the pressure it places on them
36
What is the aim of pre-infection defense?
To mimimise exposure to infection or to reduce risk of successful entry and eshtablishment of a parasite/pathogen These are often behavioral
37
What are 5 strategies and examples of avoidance behaviour?
Avoid infected areas or foods - disgust response in food Migration - in reindeer its shown to reduce parasite load Shift activity times - ants shift activity to avoid parasites Avoids infected individuals - mice avoid based on scent of urine odors allows for mate choice and transmission reduction Hygiene - some social insects remove waste from nests, grooming behaviour
38
What are the changes in great tits when broods show signs of infection?
Infested broods increase time spent begging Increased intrabrood variance (sibling fighting) Males have a large increase in investment time Females increase time invested but not as large as males
39
What is an example of anticipatroy defense?
Prophylatic self medication - wood ants preferentilly gather solidified conifer resin - which inhibits the growth of bacteria and fungi in the nest
40
What is the selfish herd?
A theory to describe anti-predator activity in which individuals at the centre of the herd are less likely to be preyed upon
41
Does the selfish herd apply to parasite protection?
Its not clear cut but some soical groups have shown a reduced risk of parasitism
42
What is the hypothesis that correlate the selfish herd theory to parasitism?
The encounter dilution hypothesis - predicts per capita number of insect bites decrease with larger groups (not just insect bites)
43
In parasites what is the difference when natural selection selects for host resistance or tolerance?
Selection for resistance - high virulence Selection for tolerance - no selection for virulence Neither - lack of host-parasite parasite co-evolution
44
In hosts what is the difference when natural selection selects for host resistance or tolerance?
Selection for resistance - immunopathy Selection for tolerance - low mortality Neither - high mortality
45
What are 3 behavioural strategies in reducing pathogens?
Reduced food intake - crickets opt for lower fat diet when immune challenged - possible trade off between immune system and energy input for digestion Behavioural fever - some organinisms seek to raise temperatures to kill parasites (resitance) and other (drosophila and bees) lower temperature to impede parasitic development (tolerance) Grooming and hygiene
46
What are the two types of cells that come from stem cells which further differentiate into different immune system?
Lymphoid progenitor Myeloid progenitor
47
Which immune cells differentiate from the lymphoid progenitor?
Dendritic cell T-cells (including T-helper and T-cytotoxic) B-cell NK (innate lymphocyte cell)
48
What are the different immune cells that differentiate from the myeloid progenitor?
Megakaryocyte - further produce platelets Monocyte - can differentiate into macrophage and dendritic cells Neutrophil Basophil Eosinophil Mast cell Erythroblast - develops into erythrocyte
49
Where does most of the initial cell differenciation occur?
Bone marrow
50
Where do t-cells undergo development?
Thymus
51
Where do Dendritic cells, t-cells, b-cells and NK cells develop?
In the periphery Dendritic cells can also develop in tissues from stemming from monocytes
52
What is the name of the progenitors to monocytes, neutrophil, basophil and eosinophil?
Granulocytes
53
Where do monocytes, neutrophil, basophil, eosinophil and enthrocyte spend their cell cycle?
In the blood
54
What are 2 componets to hummoral defence?
Immunoglobulins Complement
55
What are immunoglobulins?
Proteins that bind to foreign bodies marking them as foreign to the rest of the immune system
56
What are complements?
A complex cascade which ends in the formation of the Membrane Attack Complex (MAC) which forms pores in the cell wall and causes parasites to lyse
57
What happens during inflammation?
Early response Plasma and blood cells move to infection site Interferons (signalling proteins) and cytokine (cell signaling) cascades attract leukocytes Immune cells and humoral elements act to contain and destroy the infection
58
What is the innate response?
Includes pathogen recognition receptors on toll like receptors and elements involved on complement pathways and phagocytosis Germline encoded Fast but very generalised response Works by recognition of pathogen associated molecular patterns (PAMPS)
59
What is the adaptive response?
Specific response but slower to click in (days rather than minutes or hours) Includes T and B cells with antigen specific functions directed by the Major Histocompatibility (MHC)
60
Why is heterozygous important for immune response?
As this means that the organism has an advantage in having a 2 immune responses compared homozygous which only has 1
61
What is negative frequency dependence?
Where the gene has greater fitness benefit the less it appears in the overal gene pool
62
What is positive frequency dependance?
Where the fitness of a gene increases the more its in a gene pool

Sem 1: Parasite and pathogen ecology (11 decks)

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