BIO220 Lecture 11

Question 1

What is a phenotype?

Answer 1

Any observable characteristic or trait of an organsim

Question 2

Phenotype is determined by… (standard view)

Answer 2

Genotype and environment

Z = G + E

Question 3

Who came up with the notion of extending phenotype outside the cell?

Answer 3

Dawkins

Question 4

What does extending phenotype mean?

Answer 4

1. Things produced by individuals
2. Things produced by several individuals
3. Things produced in other individuals

Question 5

Example of extended phenotype: things produced by a individual

Answer 5

Bower nest (blue items):

• subject to genetic & environmental variation
• influences fitness
• subject to selection

Question 6

Example of extended phenotype: things produced by several individual

Answer 6

Beaver dam building:

- gene encodes for building taller dams

Question 7

Example of extended phenotype: things produced in other individuals

Answer 7

Parasites manipulate host behaviour

Question 8

Explain why things produced in other individuals is also a part of this individual’s phenotype

Answer 8

Dawkins: an individual’s behaviour will maximize survival of the genes corresponding to that behaviour, whether or not those genes happen to be in the body of the individual performing the behaviour.

Question 9

3 categories of exteneded phenotypes exhibited by parasites

Answer 9

1. Behavioural modification
2. Morphological modification
3. Molecular modification

Question 10

Examples of behavioural modification by the parasite (7)

Answer 10

1. Increase host risk taking & aggression (rabies, toxoplasmosis)
2. Increase vector biting rate (malaria)
3. Modify vector feeding preferences (malaria)
4. Alter host micro habitat preference (cockroach)
5. Death grip (ant)
6. Cocoon web construction (spider)
7. Host suicide (horsehair worm in crickets)

Question 11

Parasite increase host risk taking & aggression

Answer 11

Rabies & toxoplasmosis:

Increase transmission to new host

Question 12

Toxoplasmosis

Answer 12

Disease transmitted through cat poop.
Ideal host: cat gut
Intermediate host: mice

Infected mice will go towards cat; more likely to be eaten by cat so pathogen can end up in cat gut.

Question 13

Parasite increase vector biting rate / persistence

Answer 13

Malaria carrying mosquitoes bite more people, and return to bite if first attempt unsuccessful.

Increase transmission rate.

Question 14

Parasite modify vector feeding preferences

Answer 14

Mosquitoes more likely to bite hosts with transferable form of malaria

Question 15

Parasite altering host microhabitat perference

Answer 15

Parasitic worm infected cockroaches tend to stay in the sun; more likely to be noticed by predator (parasite’s final host)

Question 16

Enslaver parasites and death grips

Answer 16

Parasite controls where host dies.
Fungal infection in ant causes ant to have a death grip on a twig when it dies. Fungal spores burst from ant head. Location could facilitate future growth.

Question 17

Parasite change web construction of spiders

Answer 17

Parasitic wasp infect orb-weaving spiders.
Larvae grow in spiders -> manipulates spider to make cocoon web to protect pupae -> larvae kill spider and pupation stage occurs

Question 18

Can spiders be saved from cocoon web construction?

Answer 18

Yes, if the larvae/infection is killed off before cocoon web is constructed. Web making behaviour will MOSTLY return to normal.

Question 19

Parasites cause host suicide

Answer 19

Juvenile horsehair worms make crickets (host) to go into water. Will cause death for cricket, but allow horsehair worm to to to ideal environment.

Question 20

Which horsehair worm is parasitic?

Answer 20

Juvenile

Question 21

Examples of morphological modifications by the parasite

Answer 21

1. Mimicry in ants

2. Mimicry in snails

Question 22

Parasite-induced mimicry (ants) is caused by which parasite?

Answer 22

Nematatodes

Question 23

Parasite-induced mimicry (ants)

Answer 23

Nematode cause last abdominal segment in ant to swell up like a berry

• > bird attracted to berry-ant
• > ant will go infect rest of its colony

Question 24

Ideal host for nematodes?

Answer 24

Bird gut

Question 25

Intermediate host for nematodes?

Answer 25

Ants

Question 26

Parasite-induced mimicry (snails) is caused by which parasite?

Answer 26

Trematode (L. paradoxicum)

Question 27

Parasite-induced mimicry (snails)

Answer 27

Snail eye-stalks resemble caterpillars; snails aren't able to see as well to avoid predators. Make snail more likely to be eaten by birds.

Question 28

Ideal host for trematodes?

Answer 28

Birds

Question 29

Intermediate host for trematodes?

Answer 29

Snails

Question 30

Some snails infected by trematodes live ____

Answer 30

longer

Question 31

Are parasites really causing extended phenotype in hosts? (hypothesis)

Answer 31

1. Trait is adaptive for parasite 2. Trait is adaptive for hosts 3. Trait is coincidental by-product of infection

Question 32

Analysis of examples: parasite increase vector biting rate / persistence

Answer 32

By-product of infection: | mosquitoes that bite more die sooner

Question 33

Analysis of examples: worm cause cockroach to go into sun

Answer 33

Host adaptation: | worms want cooler temperature to grow, going into sun will stop development

Question 34

Analysis of examples: death grip in ants

Answer 34

Parasite adaptation: Uninfected ants like to go high in trees. Infected ants stay low to the ground. Any other elevation lead to bad results for the parasite, so it is the parasite causing the ant to go to specific location.

Question 35

Analysis of examples: cocoon web construction

Answer 35

Parasite adaptation: - without cocoon nest, pupae tend to die in the rain - removing parasite causes spider web-making behaviour to almost return to normal

Question 36

Analysis of examples: host suicide

Answer 36

Parasite adaptation: - huge cost to host - infected hosts more likely to jump in water - rescued hosts jump back into water

Question 37

Analysis of examples: zombie snails

Answer 37

No answer: complex trait

Question 38

Preferred host by L. paradoxicum

Answer 38

wide variety of bird species

Question 39

What would give a answer to the type of adaptation zombie snails are?

Answer 39

Quantify if there is an increase in predation of snails that are infected.

Question 40

Why is it important to understand the adaptation behind parasite induced behaviours?

Answer 40

1. Possible treatments 2. Control vector behaviour to reduce infection 3. Do proper science