Hw 3

Question 1

The theory of parasites negatively correlating with IQ is largely ____. Other ideas that cause lower IQs in developing nations?

Answer 1

Unproven

substandard diets

Question 2

Transmission cycle of liver fluke

Answer 2

1) Ants consume slime of a passing snail
2) Slime is loaded with the eggs of a parasite called the Liver Fluke (flat worm)
3) Live fluke burrows in an ants brain to carry them to their next host
4) Liver fluke can switch the ants behavior on and off causing the infected ants to place themselves in easy to eat positions
5) Cows ingest fluke larvae
6) worms burrow out of the stomach into the liver where they develop into adults and eat liver tissue
7) Worms then lay eggs that are excreted from the liver into the bile duct and produced in the feces

Question 3

Asexual reproduction

Answer 3

• produces more offspring over time
• always expected to have the advantage over sexual reproduction if all things are equal
• Asexual reproduction wins when disease or parasite are not of great issue

Question 4

Sexual Reproduction

Answer 4

• allows organisms to reshuffle their genes

- Sexual reproduction has the advantage when disease becomes more prevalent

Question 5

What advantage did sexual breeding topminnows have?/

Answer 5

lower rate of infection by parasites because they could create new genetic combos through gene reshuffling

Question 6

Modeling predicts that sexual repro wins under conditions of high _____ and high ____. Why

Answer 6

probably of parasite transmission; effect of parasite on biology or host

sexual reproduction is only worth it when probability of being negatively affected by parasites

Question 7

It was hypothesized that organisms with more high developed epidemic traits will be exposed to ____. Species with more sexual sexual selection____ at risk for damaging parasites.

Answer 7

more types of parasites; more

Question 8

How did researchers test the epidemic trait/parasite risk hypothesis with birds?

Answer 8

analyzed blood smears for parasites and rate species on showiness and song. Incidences of disease were compared w/these factors.

Question 9

What were the results of parasite/showiness study? Why did sexual dimorphism decline on islands?

Answer 9

positive relationships between diseases present and epidemic traits. Female brightness had the lowest coefficient compared to male brightness and song.

not as many parasites on islands

Question 10

Body weight correlated strongly with _____ . Larger bird were more likely to have _____. Give a reason this might be true?

Answer 10

disease susceptibility

parasitic protozoan infections

bigger targets

Question 11

Virulence

Answer 11

severity of disease

Question 12

Vertical transmission

Answer 12

passed from parents to offspring

Question 13

Horizontal transmission

Answer 13

passed between individuals in the same generation

Question 14

In the bird study of transmission, what were the vertically and horizontally transmitted parasites?

Answer 14

Vertical- feather feeding lice

Horizontal- blood sucking mites

Question 15

How did mode of transmission affects birds in the study?

Answer 15

Vertically transmitted lice- no significant effect on bird survival or their offspring

Horizontally transmitted mites: lower hatching success, lower post fledgling survival, fewer surviving offspring. Did not affect adult bird survival or body

Question 16

Lateral transmission favors ____ virulence.

Answer 16

high

Question 17

The parasite is generally _____ virulent in it definitive host than its intermediate hosts.

Answer 17

less

Question 18

Sexually transmitted parasites are ____ virulent than parasites not transferred this way.

Answer 18

less

Question 19

Parasite effects used to be believed to be due to _____. it is now known they _____.

Answer 19

nutritional demands and drain on potential energy

go beyond this

Question 20

Parasites induce behavior in their hosts that make them more vulnerable to _____.

Answer 20

predation

Question 21

Parasitism plays a role in the maintenance of ________.

Answer 21

sexual reproduction

Question 22

most modern theories of sexual dimorphism treat flashy non combat displays and morphology of males as advertisements that they are ____.

Answer 22

parasite free or can tolerate parasites so as to grow ornaments. Advertising good genes

Question 23

A few studies have indicated that strains or dif species of parasites. It is the ____ virulent that achieves the highest transmission or report benefit

Answer 23

most

Question 24

Parasites ____ to a host are more virulent than parasite known long associated w/a particular species of host.

Answer 24

new

Question 25

How do we know how long a parasite has associated w/host?

Answer 25

phylogenetic trees

Question 26

Vertical transmission favors ____ virulence. Why?

Answer 26

low

this way parental generation is alive and healthy enough to produce to infect next gen

Question 27

In lateral transmission, selection favors parasite that reproduces ____ and whose young are dispersed to _____ despite ____.

Answer 27

quickly

new individuals despite its effect on original host

Question 28

Anything that compromises host survival will lead to _____. Give example. Why?

Answer 28

more virulence

predation pressure exists on a host, parasite will respond w/more virulence so as to reproduce more in shorter period of time

Question 29

Why are sexually transmitted parasites less virulent than others?

Answer 29

1. types of parasites are more host specific

2. essentially directed all of hosts energy into production of more parasites and little to gain from hosts demise.