Evolutionary Medicine

Question 1

What are the six reasons for vulnerability that arise due to the characteristics of natural selection? (6)

Answer 1

1. Mismatch with modern environment
2. Pathogens co-evolving with host
3. Every trait is a trade-off
4. Contrains on selection
5. Selection maximizes reproduction (not health)
6. Defences such as pain and fever are useful

Question 2

What does the ‘reason for vulnerability’ “mismatch with modern environment” refer to?

Answer 2

Our bodies did not evolve to cope with novel environments. Selection and evolution to adapt to these new environments is slow.

Question 3

What kind of diseases can often be explained by the fact that evolution is at a mismatch with the modern environment?

Answer 3

Chronic diseases

Question 4

Pathogens frequently evolve [faster/slower] than their hosts

Answer 4

Faster
This allows pathogens to continuously stay infective to their host species

Question 5

What allows pathogens to evolve faster than their hosts?

Answer 5

Pathogens frequently have a shorter reproductive cycle, allowing them to evolve faster

Question 6

What is the evolutionary definition of ‘fitness’?

Answer 6

Reproductive success

Question 7

What is the evolutionary defintion of reproductive success?

Answer 7

Number of offspring + whether they are fertile

Question 8

What is a proximate explanation?

Answer 8

Mechanistic explanation: how does a trait work?

Question 9

What is an ultimate explanation?

Answer 9

Evolutionary explanation -> how was a certain trait selected for = how does a trait increase fitness?

Question 10

Why are diseases that occur at older are not/barely selected against?

Answer 10

They don’t impact the reproductive success of a species -> genes have already been passed on at that point

Question 11

What is the primary force shaping the evolution of a species?

Answer 11

It’s environment

Question 12

How many generations does it take for a new trait to establish?

Answer 12

~50-100 generations

Question 13

Why can disease-causing genes sometimes persist?

Answer 13

Apparently they offer the species some sort of advantage when it comes to fitness, and therefore persist in the poulation

Question 14

What are so-called neutral traits?

Answer 14

Variations that are not correlated with reproductive success

Question 15

Which four major ways does the body have to deal with pathogens?

Answer 15

1. Avoidance
2. Resistance
3. Immune tolerance
4. Disease tolerance

Question 16

What is immune avoidance? Name two examples.

Answer 16

Mechanisms preventing host exposure to microbes

1. Anatomic barriers
2. Particular behaviours

Question 17

What is immune resistance?

Answer 17

General immune strategy, aimed at reducing or eliminating pathogens

Question 18

What is immune tolerance?

Answer 18

Lack of response to an antigen

Question 19

What is disease tolerance?

Answer 19

Balance between limitation of health/fitness due to the cost of infection vs. the worth of fighting off the disease

Question 20

In which circumstances is disease tolerance favourable over immunity against a disease?

Answer 20

When fighting off the disease costs more energy and resources than the disease persisting

Question 21

What is ‘adaptation’?

Answer 21

A trait that increases the ability of an individual to survive or reproduce, compared to individuals without a trait. Also: the process that produces that state.

Question 22

What is ‘antagonistic pleitropy’?

Answer 22

One gene has positive effects on fitness through its impact on one trait, but negative effects on fitness through its impact on another trait.

Question 23

What is ‘coevolution’?

Answer 23

Evolutionary changes in one thing (genes, sexes, species) induce evolutionary changes in another, and vice versa.

Question 24

What is ‘Darwinian fitness’? (2)

Answer 24

1. The extent to which an individual contributes genes to future generations
2. An individual’s score on a measure of performance correlating with genetic contribution to future generations

Question 25

What is 'evolution'?

Answer 25

Changes in allele frequencies over time, and the phenotypic changes that result from that

Question 26

What is 'genetic drift'?

Answer 26

Random chance in allele frequencies due to chance factors

Question 27

What is the 'grandmother mypothesis of menopause'?

Answer 27

Menopause is a life history adaptation assocation with the contribution grandmother make to feeding their grandchildren

Question 28

What is 'kin selection'?

Answer 28

(Older) relatives promote the reproductive success of (younger) relatives

Question 29

What is 'natural selection'?

Answer 29

A non-zero correlation of trait variation with variation in reproductive success.

Question 30

What is 'neutral evolution'?

Answer 30

The change and occsasional fixation of alleles caused by the drift of alleles, that is not correlated wtih reproductive success.

Question 31

What is 'path dependence'?

Answer 31

A certain body design has evolved along a gradual cumulative path, and there is no way back.

Question 32

What is 'reproductive success'?

Answer 32

The number of viable, fertile offspring produced per lifetime.

Question 33

What is 'sexual selection'?

Answer 33

The component of natural selection that is associated with success in mating

Question 34

What is the 'theory of evolution by natural selection'?

Answer 34

The hypothesis that descent with mmodification is caused in large part by the action of natural selection

Question 35

What is the definition of 'pathogenic bacteria'?

Answer 35

Bacteria that are capable of inflicting damage to their host

Question 36

The majority of prokaryotes that humans interact with [is/is not] pathogenic

Answer 36

Not pathogenic

Question 37

Which three classes of bacterial pathogens can be identified?

Answer 37

1. Accidental pathogens 2. Obligate pathogens 3. Opportunistic pathogens

Question 38

What are accidental pathogens?

Answer 38

Bacteria that exist in the environment and occasionally infect humans. Infection of humans do not promote the spread of the pathogen to a new host.

Question 39

Where can accidental pathogens be found?

Answer 39

They exist in the environment as free-living bacteria or in assocation with other organisms

Question 40

Accidental pathogens are [less/more] heterogeneous than obligate pathogens

Answer 40

More heterogeneous

Question 41

What are examples of accidental pathogens? (3)

Answer 41

1. Legionella pneumophila 2. Bacillus anthracis 3. Clostridium tetani

Question 42

What are obligate pathogens?

Answer 42

Those bacteria that must cause disease in order to be transmitted form one host to another, and that can solely grow an divide in association with their host

Question 43

Obligate pathogens [are/aren't] capable of surviving in the environment

Answer 43

Obligate pathogens cannot survive in the environment

Question 44

What makes obligate pathogens dependent on their host?

Answer 44

They are highly dependent on their host, and obtain essential nutrients form their host

Question 45

What makes obligate pathogens dependent on their host for nutrients? Why is this trait an evolutionary advantage for these bacteria?

Answer 45

Lack several enzymes involved in energy metabolism These enzymes are not encoded by the genome, resulting in a smaller genome that allows for quicker replication

Question 46

What are examples of obligate pathogens? (7)

Answer 46

1. Mycobacterium tuberculosis 2. Mycobacterium leprae 3. Chlamydia trachomatis 4. Rickettsia ricketsii 5. Treponema pallidum 6. Streptococcus pyogenes 7. Yersinia pestis

Question 47

What are opportunistic pathogens?

Answer 47

Bacteria that can cause infections to humans when the immune system is not functioning property

Question 48

Opportunistic pathogens [can/can't] be transmitted to the next host without causing disease

Answer 48

They can be transmitted without causing disease

Question 49

Where can opportunistic pathogens frequently be found?

Answer 49

Colonizing their host, but not causing infection

Question 50

What are examples of opportunistic pathogens? (3)

Answer 50

1. Clostridium difficile 2. Pseudomonas aeruginosa 3. Staphylococcus aureus

Question 51

What are the steps of a prototypic bacterial infection? (5)

Answer 51

1. Exposure 2. Adherence 3. Growth 4. Invasion 5. Toxicity & spread

Question 52

What are the three main ways in which humans come into contact with bacterial pathogen?

Answer 52

1. Human-to-human 2. Animal-to-human 3. Environment-to-human

Question 53

What are the three ways in which humans get exposed to bacterial pathogens from animals?

Answer 53

1. Direct contact with animals/droppings 2. Consumption of contaminated animal products 3. Vector mediated zoonoses

Question 54

What are the two ways in which bacteria can adhere to ECM?

Answer 54

1. Specific 2. Non-specific

Question 55

What is a common non-specific adherence mechanism of bacteria? Which two subtypes can be identified?

Answer 55

Polysaccharides, in: 1. Diffuse slime 2. Compact capsules

Question 56

What are two specific bacterial adherence mechanisms?

Answer 56

1. Polysaccharides 2. Proteins

Question 57

What is a common specific bacterial adherence mechanism using polysaccharides?

Answer 57

Teichoic acid

Question 58

What are three protein-based specific bacterial adherence-mechanism?

Answer 58

1. Pili/fimbriae 2. Lectins 3. Microbial surface components recognizing adhesive matrix molecules (MSCRAMM)

Question 59

What is the main problem for bacteria while trying to grow?

Answer 59

Availability of nutrients

Question 60

Which nutrient is hard to access for bacteria that try to grow in humans? Why is this nutrient hard to access?

Answer 60

Iron -> sequestered within erythrocytes and bound with high affinity to hemoglobulin

Question 61

What are bacterial mechanisms to obtain iron? (3)

Answer 61

1. Siderophores 2. Membrane damaging molecules 3. Enzymes

Question 62

What are siderophores?

Answer 62

Iron-chelating compounds

Question 63

What are the selective pressures on bacterial pathogens, causing them to evolve? (5)

Answer 63

1. Defence systems of other micro-organisms 2. Host defence systems 3. Disinfection 4. Vaccination 5. Antimicrobial therapy

Question 64

Which traits are often encoded by the core genome of bacteria?

Answer 64

Genes that allow bacteria to survive and thrive in their respective niches

Question 65

What kind of microbes does the stomach select for?

Answer 65

Acid-resistant microbes

Question 66

What kind of microbes does the respiratory tract select for?

Answer 66

Aerobic microbes

Question 67

What kind of microbes does the (lower) intestinal tract select for?

Answer 67

Anaerobic/facultative aerobic bacteria

Question 68

What kind of microbes does the skin select for?

Answer 68

Drying-resistant bacteria

Question 69

Which traits are often encoded by mobile genetic elements of bacteria? (3)

Answer 69

1. Toxins 2. Capacities to deal with the innate immune system 3. Capacities to deal with the adaptive immune system

Question 70

What are important bacterial capacities allowing them to deal with the innate immune system? (2)

Answer 70

1. Innate immune evasion 2. Survive phagocytosis

Question 71

What are important bacterial capacities to deal with the adaptive immune system? (5)

Answer 71

1. Covering up in poorly immunogenic capsules 2. Hiding in biofilms 3. Producing proteases 4. Spontaneous mutation & recombination 5. Loss/obtaining of certain genes

Question 72

What are the bacterial mobile genetic elements?

Answer 72

1. Plasmids 2. Bacteriophages 3. Transposons 4. Insertion sequences 5. Genomic islands

Question 73

What are the mechanisms that bacteria use to adapt to antimicrobial therapies? (3)

Answer 73

1. Hiding in biofilms 2. Spontaneous mutation/recombination 3. Exhange of genetic materials