Deck 10: The Evolution of Disease

Question 1

What causes malaria?

A) Particular types of mosquito
B) Contaminated water
C) Contact with tropical primates
D) Particular species of protozoan
E) Crowded conditions at high temperatures

Answer 1

D

Question 2

Is malaria treatable?

A) Yes. Quinine and a dozen other drugs handle most types.
B) No. It's the most deadly disease in human history.
C) Yes. But there are different drugs to treat malaria and none is effective against every strain of protozoa which can cause the disease.
D) No. All the malaria-causing protozoa are resistant to all our drugs now.
E) Yes. It's always treatable but not everyone can afford the drugs.

Answer 2

C

Question 3

In general, how does the malaria-causing bacteria Plasmodium, increasingly resistant to our drugs?

A) Natural selection and evolution
B) Overuse of the drugs
C) People taking the drugs incorrectly
D) Increasing mutation rates due to environmental pollution
E) Random changes in genes

Answer 3

A

Question 4

Without drugs, do humans have any inborn defenses against malaria?

A) Yes. The immune systems of some people automatically recognize the pathogens involved and they remain uninfected.
B) No. That's why it's the most deadly disease in human history.
C) Yes. Certain genetic mutations like the one that causes sickle-shaped red blood cells offer some resistance to it.
D) No. That's why the organisms that cause it are able to mutate so easily.
E) Yes. Certain genetic mutations make a small percentage of people completely resistant to the infection.

Question 5

About how long has malaria been around?

A) It's relatively recent, and we haven't adapted yet. That's why it's so deadly.
B) DNA of the pathogen involved has been found in dinosaur fossils.
C) Single-celled organisms were the first living things on Earth, so early in the history of the Earth-billions of years.
D) At least as long as humans have been around
E) There's no way to know.

Question 6

Is it true that your body is mostly made up of your own cells?

A) Yes, most of the cells making up your present body originated with you.
B) Yes, but there are a lot of bacterial cells and other organisms that live on you, too.
C) Yes, all of cells making up your present body originated with you.
D) No. The majority of "your" cells are bacteria or other organisms living on you.
E) There is no way to really distinguish "your" cells from other cells living in or on you, so the answer to this question is not clear.

Question 7

About how many species of bacteria live in your mouth?

A) None, I hope!
B) At least 10
C) At least 100
D) At least 700
E) More than 1200

Question 8

The study of the interactions among species and their physical environments is called what?

A) Biology
B) Ecology
C) Zoology
D) Physiology
E) Immunology

Question 9

Is it reasonable to consider a human body to be an ecosystem?

A) No. It's just one body. An ecosystem includes a whole system of interacting species.
B) Yes. We have organ systems so that combined with us being an organism makes us an ecosystem.
C) No. An ecosystem is something outside in nature.
D) Yes. Many organisms living in and on "our" environment compete, reproduce, and evolve, so combined, we are a working ecosystem.
E) No. An ecosystem includes abiotic factors. A human is biotic.

Question 10

Which of the following interactions is an example of commensalism?

A) Eyebrow mites and humans
B) Bacteria in our digestive tract helping us to digest food
C) Bacteria in our digestive tracts
D) An infection by a malaria-causing bacteria species
E) Insects eating crops

Question 11

What is an example of how the bacterial species living on us compete with each other?

A) Secreting toxic compounds
B) Making habitats acidic
C) Forming slippery films preventing others from attaching
D) Using up critical nutrients
E) All of the above

Question 12

How is competition between the various microscopic organisms that live on us a good thing for us?

A) We don't wind up with hundreds of species living on us.
B) Only beneficial species can ever survive on us.
C) The "good" species make it difficult for any "bad" ones to move in and cause disease.
D) They keep us clean.
E) Doctors can identify diseases on us early, as a result of these.

Question 13

Which of the following is an example of a mutualistic relationship?

A) Eyebrow mites and humans
B) Healthy bacteria creating too acidic an environment for unhealthy bacteria to live in
C) Bacteria in our digestive tract getting nutrients for themselves by helping us digest our food
D) Pathogens causing a disease in a human
E) A genetic mutation reducing the effects of malaria

Question 14

Many bacteria do not interact with humans, but those that do can always be classified as either harmful or not harmful to humans. True or False?

A) False. Some get worse as they age.
B) True. They always either hurt us or they don't.
C) False. No bacteria species is always bad for us all the time.
D) True. Once they mutate to be harmful, they stay that way.
E) False. Some are fine in small numbers, but in big numbers they can overwhelm the immune system and cause problems.

Question 15

What is an example of a type of organism which is always harmful to a cell?

A) A bacterium
B) An antibiotic
C) A fungus
D) A virus
E) Nothing is always harmful.

Question 16

What was the source for the drug penicillin, and what type of drug is that?

A) Fungus; antibiotic
B) Mold; antibiotic
C) Bacteria; antibiotic
D) Fungus; analgesic
E) Mold; analgesic

Question 17

How does a population of pathogens become resistant to a drug?

A) Natural selection: the drug selects against the most resistant.
B) Evolution: a mutation occurs as a result of exposure to the drug
C) A lucky mutation
D) Natural selection: some are resistant to start, and those survive and reproduce.
E) A few become resistant at first exposure, and they survive and reproduce.

Question 18

Pathogens have four ways to resist antibiotics: 1) antibiotic can't get through cell membrane, 2) produce an enzyme that breaks down the antibiotic, 3) alter the structure of the antibiotic's target so it's not vulnerable, 4) pump out the antibiotic. How do these changes in the pathogens happen so they become resistant?

A) These changes are the result of repeated exposure to the antibiotic.
B) These changes are the result of genetic mutations.
C) Repeated horizontal gene transfer
D) Reproducing quickly in the presence of the antibiotic
E) Cross-breeding between pathogens

Question 19

A resistant bacterium can share its resistance with its neighbors through what processes?

A) Transcription, translation, conduction
B) Transfer, transduction, conduction
C) Transformation, transduction, conjugation
D) Transcription, transfusion, conjugation
E) Transformation, translation, conjugation

Question 20

If resistance is possible, why aren't all bacteria resistant to antibiotics by now?

A) They don't reproduce quickly enough to all become resistant.
B) The mutations causing resistance are very rare.
C) They can't easily share their resistance across a population.
D) Maintaining resistance leaves less energy for reproduction, so non-resistant bacteria do better in general.
E) Not all antibiotics work.

Question 21

Why do hospitals tend to harbor particularly resistant strains of bacteria?

A) Because there are lots of sick people
B) Because they can't keep them as clean as they should
C) Because there are antibiotics in use continuously so there is time for mutations for resistance to be shared among the bacteria populations
D) Because there are antibiotics in use continuously so there is time for bacteria to evolve resistance in response.
E) It's not clear why this is since hospitals are generally careful about cleaning and sterilizing.

Question 22

It makes sense that you should take antibiotics long enough to kill off most of the pathogens affecting you, but why shouldn't you take them for too long?

A) They can have unpleasant side effects.
B) If you expose the pathogens to antibiotics for too long, those with resistance will have time to outcompete the non-resistant variations and the whole population will be resistant.
C) If you expose the pathogens to antibiotics for too long, there will be time for them to evolve mutations allowing resistance to the antibiotics.
D) You won't just kill all the pathogens in your body, but also most of the bacteria that you need to stay healthy.
E) If humans take antibiotics for too long, they'll become resistant to them.

Question 23

Why are low doses of antibiotics commonly used in animals in industrial farming operations?

A) Killing some of the bacteria taking up nutrients in the guts of the animals leaves the animals more nutrients so they grow faster.
B) Low doses of antibiotics kill off any pathogens that might infect the animals, saving veterinary costs.
C) Any meat taken from these animals is essentially "purified" and pathogen-free.
D) They eliminate any pathogens that might be introduced by insects, common when a lot of animals are in one place.
E) People pay more for antibiotic-treated foods.

Question 24

The virus myxoma was introduced into Australia to try to limit a population explosion of rabbits introduced from Europe. Did it work?

A) Yes, the virus killed 99% of the rabbits almost immediately.
B) Yes, the virus killed 99% of the rabbits initially and then kept the population down at manageable levels.
C) No. At first it did, but then the rabbits evolved to be resistant, and now it doesn't work at all.
D) Yes. At first it worked, but then only resistant rabbits were left, so the virus changed to become less virulent. That allows the virus to be more easily spread though, so the rabbit populations are still somewhat controlled.
E) No. The virus almost immediately became less virulent such that it spreads more easily but it doesn't kill the rabbits.

Question 25

In pathogens, what does natural selection select for?

A) Deadliness
B) Ease of transmission
C) Reproductive success
D) Speed of growth
E) Antibiotic resistance

Question 26

In addition to outcompeting other bacteria in the host, what else do pathogens have to do to survive over the long term?

A) Kill of their host
B) Get to the next host
C) Develop resistance to antibiotics
D) Infect a different species of host
E) Grow quickly

Question 27

For what does the trade-off hypothesis offer an explanation?

A) Why some pathogens infect humans and some don't
B) Why some humans are resistant to some pathogens but not others
C) Why some pathogens are successful over time and some aren't
D) Why some pathogens develop resistance to antibiotics
E) Why some pathogens are more virulent than others

Question 28

In the trade-off hypothesis, what is being "traded off?"

A) Resistance versus virulence
B) Reproduction in the host versus virulence
C) Transmission versus virulence
D) Reproduction in the host versus ease of transmission
E) Reproduction versus death rate

Question 29

A malaria infection almost immediately puts a sick person in bed. If the pathogen has to infect other people, wouldn't it be better if it weren't quite so bad initially, so the victim could get around?

A) Yes, but malaria is transmitted by mosquitoes, not humans, so it doesn't matter if the infected human is confined to bed right away.
B) Yes, but all pathogens are selected to make the host as sick as possible as quickly as possible.
C) Yes, but since we have no effective drugs, this is what happens.
D) No, because "germs" like malaria spread person to person easily through the air, so an infected person doesn't need to actually contact another one to transmit the pathogen
E) No, because then the pathogen wouldn't be reproducing quickly enough to outcompete the normal bacterial population on the person

Question 30

A highly-virulent pathogen is reproducing in the host most quickly, so it should "win," and therefore most pathogens should evolve to be highly virulent. Why don't they?

A) Pathogens don't evolve like other living things.
B) Natural selection wouldn't select for "deadliness."
C) Some pathogens can't reproduce that fast so they never get to the point where they kill the host.
D) Most pathogens are highly virulent.
E) A highly virulent pathogen may be less likely to infect more humans if it disables the first host too quickly.

Question 31

According to the trade-off hypothesis, why are diseases like mumps, measles, or chickenpox rather mild?

A) The viruses reproduce very quickly and die before symptoms get too bad.
B) Mostly children get these diseases.
C) They're highly contagious already.
D) They require direct human-to-human contact to spread so the human hosts can't be too sick to get around.
E) They require direct contact with infected insects so the human hosts can't be too sick to get around.

Question 32

The disease cholera is highly virulent and is spread by contact with infected water. Does this support the trade-off hypothesis of disease virulence?

A) Yes because it's easy to come into contact with water directly. There is no need to keep the host up and about for transmission.
B) Yes because the only way you the disease is by contact with water and it's not particularly deadly
C) Yes, because it's not easy to come into contact with water directly. No need to keep the host up and about for transmission.
D) No, you'd expect a waterborne pathogen to not be particularly deadly.
E) No, but neither does influenza.

Question 33

Does the typical pattern of symptoms for a sexually- transmitted disease make sense in light of the trade-off hypothesis?

A) Yes. Symptoms are often so mild that people are unaware they have the disease; therefore, the disease is more likely to get transmitted to the next host.
B) Yes. The diseases are often deadly, quickly, which makes sense because it's so easy for them to be transmitted to the next host.
C) No. Symptoms are often so mild people are unaware they have the disease, which also makes transmission to the next host highly unlikely.
D) No. The diseases are often deadly, quickly, which doesn't make sense because this makes transmission to the next host highly unlikely.
E) No, but the majority of diseases don't follow the predicted pattern.
10)4

Question 34

Where do new diseases most commonly originate?

A) China
B) Pathogens from other species that jump to humans
C) Mutations
D) Crowded cities
E) Pollutants that contaminate water sources

Question 35

What are the four stages of a new infectious disease?

A) Transmission, infection, exposure, epidemic
B) Infections, transmission, exposure, epidemic
C) Exposure, infection, transmission, epidemic
D) Exposure, transmission, infection, epidemic
E) Transmission, exposure, infection, epidemic

Question 36

We get very few infections resulting from the many pathogens to which we are exposed. Why is this?

A) Good luck
B) Effective antibiotics
C) Mutations
D) Our immune system
E) Genetics

Question 37

Over time, how does a pathogen normally get better suited to infect and transmit?

A) Mutations
B) Increased human contact
C) Resistance to drugs
D) Incorrect use of drugs
E) Natural selection

Question 38

Why is the HIV that causes AIDS particularly dangerous? What does it do to people?

A) It makes people very sick.
B) It attacks the brain.
C) It weakens the very immune system that could fight it.
D) It infects them with chimpanzee antibodies.
E) Scientists are not sure what it does exactly.

Question 39

Why can't antibiotics be considered an effective long-term strategy for controlling disease?

A) We're unlikely to find new ones that work.
B) Pathogens will keep evolving resistance.
C) Most antibiotics don't work anymore.
D) People won't take them as prescribed.
E) They're too expensive.

Question 40

Most vaccines cause the formation of antibodies against a particular pathogen, but if the pathogen mutates quickly, the vaccines don't stay effective. How does the vaccine against diphtheria work that avoids this problem?

A) Diphtheria doesn't mutate quickly, so the vaccine works for awhile.
B) The vaccine only works against the diphtheria that produces toxins.
C) Because the vaccine works against the toxin produced, not the bacteria cell itself, mutations to the cell don't alter the vaccine's effectiveness.
D) The vaccine works against the bacteria cells directly, so they don't have time to mutate.
E) The vaccine is naturally selected for, so it adjusts to the mutations in the bacteria.

Question 41

If human behavior were to change, making HIV much less easily transmittable, what might happen to the virus according to the trade-off hypothesis?

A) It would become more deadly.
B) It would become less deadly.
C) It would gradually disappear from the population.
D) Humans would gradually get more resistant.
E) It would start reproducing much more quickly.

Question 42

Why do humans continue to get sick due to infection by pathogens, even with modern sanitation and medical care?

A) Pathogens continue to evolve to overcome our defenses.
B) We're covered in a whole ecosystem of bacteria, fungi, mites and worms.
C) Our antibiotics don't work for long.
D) Our vaccines don't work for long.
E) We live in overcrowded areas.

Question 43

Dr. Ewald got interested in host-pathogen interactions as a result of considering what question under what circumstance?

A) He came down with malaria while doing a field study and wondered where it came from.
B) He had a severe case of diarrhea and wondered whether that was his body's way of getting rid of an organism, or the organism's way of infecting the next host.
C) His mother developed Alzheimer's disease and he wondered whether it was possible that the disease resulted from a chronic, long-term infection.
D) He was director of a program of disease evolution and he wondered whether heart disease was the result of the evolution of a chronic infection.
E) He actually had several experiences with diseases and in every case wondered how the host evolved in the presence of that particular pathogen.

Question 44

What does Dr. Ewald study?

A) Treatments for diarrhea
B) Alzheimer's disease
C) Birds, although from a disease standpoint
D) Evolution of bird disease
E) Evolutionary medicine
"Technology Connection"

Question 45

What do antibodies do?

A) Ingest and destroy specific "foreign" pathogens in your body
B) "Remember" previous pathogens you've been infected by
C) Pathogens produce them to incapacitate your immune system
D) Identify specific "foreign" particles in your body so other immune system cells can ingest and destroy them
E) Recognize "foreign" pathogens in your body so the immune system can respond

Question 46

Why don't "live" vaccines make you sick?

A) They've been allowed to adapt to non-human conditions such that they no longer affect humans.
B) They aren't really alive.
C) They are taken as a nasal spray rather than being injected into the blood stream.
D) Your immune system recognizes them right away.
E) They aren't made up of complete pathogens so they can't infect.

Question 47

The insecticide DDT kills mosquitoes and does help control malaria when it is first used. Why don't we use it?

A) It's extremely toxic to other organisms (including humans), and the mosquitoes quickly become resistant.
B) It's extremely expensive so the developing countries that could best use it can't afford it, and the mosquitoes quickly become resistant.
C) Malaria isn't enough of a problem that we should risk using something so toxic.
D) Screen doors and medical care work better in the short term.
E) Instead we use it to control insects on crops, and there isn't enough to go around.

Question 48

If an insecticide like DDT were found that killed mosquitoes but was otherwise perfectly safe, would the problem of malaria infection be solved for good?

A) There's no way to know for sure, but we could try it.
B) Yes. The problem would be solved.
C) Yes, but a safe insecticide is probably impossible to produce.
D) No. Malaria comes from organisms other than mosquitoes.
E) No. There would be some resistant mosquitoes, and those would live to create an increasingly resistant population until the insecticide no longer worked on them.

Question 49

How is it that scientists didn't know until fairly recently that humans carry around whole ecosystems of bacteria?

A) We didn't have strong enough microscopes to see bacteria.
B) They weren't looking for them.
C) The bacteria don't grow well in the lab, and only lately have we had the technology to identify bacterial species by RNA.
D) The bacteria don't grow well in the lab, and only lately have we had the technology to see them.
E) Bacteria have especially complex RNA, so it took awhile use that to identify species.

Question 50

Most of the bacteria and molds that grow on and in humans don't grow well in a lab. Why is this?

A) They are not very resilient, so when they are moved, they usually die in the process.
B) Labs tend to be very sterile so few organisms can survive even if scientists are trying to grow them.
C) It is generally difficult to grow specific bacteria in a lab setting.
D) These organisms tend to be very specifically adapted to their habitat on a person and that habitat is difficult to duplicate in a lab.
E) These organisms lack the usual RNA that would identify them, so it's impossible to isolate them from each other.

Question 51

What disease has probably killed more humans in history than any other and continues to do so today?

Question 52

Why is it increasingly difficult to treat malaria?

Question 53

What is the study of interactions among species and their environments called?

Question 54

When two species interact such that both benefit, what is that relationship called?

Question 55

Not all infections are the result of organisms living on us. How else to we get infections?

Question 56

What was the original source of the antibiotic penicillin?

Question 57

Why don't antibiotics work all the time?

Question 58

Bacteria don't reproduce sexually, so how do they share genetic material?

Question 59

What is virulence a measure of?

Question 60

The idea that a pathogen might have to be less deadly in order to increase its chances of getting to infect many hosts and therefore reproduce effectively is called what?

Question 61

Why might a sexually-transmitted disease benefit by not creating any symptoms?

Question 62

Where do most new diseases come from?

Question 63

What is it called when a disease reaches a final stage where it can spread widely and infect a great number of people?

Question 64

What was the original source of the HIV-1 virus that causes AIDS?

Question 65

Why is it risky to continue to use antibiotics in non-life- threatening cases, or to take them incorrectly?

Question 66

Vaccinations work well against many pathogens, but not all, like influenza and HIV. Why don't they work on these?

Question 67

According to the trade-off hypothesis, because HIV is transmitted very easily, it continues to be highly virulent. If we changed our behavior such that it wasn't easily transmittable, how might that force the virus to change in a way that would be helpful?