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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
Q

Name an example of a parasite which could reverse its parasitism?

A

Diplomonadida are a group of protists, with some are free living and some of which are parasitic - suggesting reversal is possible

26
Q

What is upward incorporation?

A

First host is the intermidiate host with the final host being a predator of the intermidiate host

27
Q

What is downward incorporation?

A

First host is the final host with an intermidiate host evolving later

28
Q

What are the outcomes of a parasite if a host goes extinct?

A

1 - Parasite goes extinct
2 - Parasite finds alternative host
3 - Shorten lifestyle

29
Q

What are the benefits to truncate your lifecycle?

A

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
Q

What is the virus first hypothesis?

A

Viruses stemmed from pre-cellular life with self repilicating based on RNA - predating the domains of life

31
Q

What is the cell first hypotheses?

A

Viruses evolved from cells that lost their components and genes becoming obligate parasites

32
Q

What are example of pre-infection host defences?

A

Barriers - skin
Secretions
Reducing exposure - not eating rotten food

33
Q

What are examples of post-infection host defence?

A

Physiological defences - immune system
Behavioural defences

34
Q

What are the types strategies for post-infection host defences?

A

Resistance - clear a pathogen at first sight
Tolerance - allowing pathogens to happen but manage the number of pathogens

35
Q

What are the pros and cons of the resistance strategy?

A

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
Q

What is the aim of pre-infection defense?

A

To mimimise exposure to infection or to reduce risk of successful entry and eshtablishment of a parasite/pathogen
These are often behavioral

37
Q

What are 5 strategies and examples of avoidance behaviour?

A

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
Q

What are the changes in great tits when broods show signs of infection?

A

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
Q

What is an example of anticipatroy defense?

A

Prophylatic self medication - wood ants preferentilly gather solidified conifer resin - which inhibits the growth of bacteria and fungi in the nest

40
Q

What is the selfish herd?

A

A theory to describe anti-predator activity in which individuals at the centre of the herd are less likely to be preyed upon

41
Q

Does the selfish herd apply to parasite protection?

A

Its not clear cut but some soical groups have shown a reduced risk of parasitism

42
Q

What is the hypothesis that correlate the selfish herd theory to parasitism?

A

The encounter dilution hypothesis - predicts per capita number of insect bites decrease with larger groups (not just insect bites)

43
Q

In parasites what is the difference when natural selection selects for host resistance or tolerance?

A

Selection for resistance - high virulence
Selection for tolerance - no selection for virulence
Neither - lack of host-parasite parasite co-evolution

44
Q

In hosts what is the difference when natural selection selects for host resistance or tolerance?

A

Selection for resistance - immunopathy
Selection for tolerance - low mortality
Neither - high mortality

45
Q

What are 3 behavioural strategies in reducing pathogens?

A

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
Q

What are the two types of cells that come from stem cells which further differentiate into different immune system?

A

Lymphoid progenitor
Myeloid progenitor

47
Q

Which immune cells differentiate from the lymphoid progenitor?

A

Dendritic cell
T-cells (including T-helper and T-cytotoxic)
B-cell
NK (innate lymphocyte cell)

48
Q

What are the different immune cells that differentiate from the myeloid progenitor?

A

Megakaryocyte - further produce platelets
Monocyte - can differentiate into macrophage and dendritic cells
Neutrophil
Basophil
Eosinophil
Mast cell
Erythroblast - develops into erythrocyte

49
Q

Where does most of the initial cell differenciation occur?

A

Bone marrow

50
Q

Where do t-cells undergo development?

A

Thymus

51
Q

Where do Dendritic cells, t-cells, b-cells and NK cells develop?

A

In the periphery
Dendritic cells can also develop in tissues from stemming from monocytes

52
Q

What is the name of the progenitors to monocytes, neutrophil, basophil and eosinophil?

A

Granulocytes

53
Q

Where do monocytes, neutrophil, basophil, eosinophil and enthrocyte spend their cell cycle?

A

In the blood

54
Q

What are 2 componets to hummoral defence?

A

Immunoglobulins
Complement

55
Q

What are immunoglobulins?

A

Proteins that bind to foreign bodies marking them as foreign to the rest of the immune system

56
Q

What are complements?

A

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
Q

What happens during inflammation?

A

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
Q

What is the innate response?

A

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
Q

What is the adaptive response?

A

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
Q

Why is heterozygous important for immune response?

A

As this means that the organism has an advantage in having a 2 immune responses compared homozygous which only has 1

61
Q

What is negative frequency dependence?

A

Where the gene has greater fitness benefit the less it appears in the overal gene pool

62
Q

What is positive frequency dependance?

A

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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