Lecture 29

Question 1

The Pinnacle of Evolution

Answer 1

• us or parasites?
• parasites are a rival to humans in the part they play in evolution
• arms race between what’s being parasitized and the parasites that is what drives evolution
• complicated interactions with prey

Question 2

Evolutionary Arms Race

Answer 2

• between predator and prey
• where predation starts to slide into parasitism-really sophisticated way to use prey species
• parasites with complex life cycles and playing with mind of your prey
• cooperation between multiple pathogens and parasites to target single prey species

Question 3

The Red Queen Hypothesis

Answer 3

• sex may be an adaptation to escape parasites

- mixing up of genes to keep them ahead

Question 4

Statistics

Answer 4

• over half of known animal species have parasite life styles in some or all of their life cycles
• one large class=parasitoids
• 20% of all insects are parasitoids

Question 5

Parasitoids

Answer 5

-parasites in juvenile stage but free-living as adults

Question 6

Braconid Wasps

Answer 6

• symbiotic relationship between parasitic wasp and polydnaviruses but pathogenic to host
• wasp doesn’t only inject eggs but also virus particles so the caterpillar becomes an incubator and the eggs hatch and consume the insects innards but not its required organs that it needs to move around and function
• virus requires wasp to complete its life cycle in order to propagate its viral genome
• expression of virus genes inactivates caterpillars immune response to the wasp’s eggs the eggs hatch then consume innards

Question 7

Dirty Bacterial Tricks Activated Once Inside Insect

Answer 7

• bacteria switch from peacefully living in nematodes to producing insecticidal toxins
• bacteria make enzyme to digest insect
• bacteria make antibiotics to ward off bacterial competitors

Question 8

Phorid Flies

Answer 8

• lay egg in thorax of ant
• larga eats innards of thorax
• when ready to pupate it crawls into head decapitating ant and adult fly hatches from head capsule

Question 9

Types of Ants

Answer 9

• soldier, worker and minima
• minima ants ride on shoulders of worker ants and fend off phorid flies
• enough selective pressure on these flies that are parasitic of these ants that it calls for a class that acts as an extra step of protection

Question 10

Mind Control Parasites

Answer 10

-don’t just take over body and behavior but also get into minds of hosts

Question 11

Birds and Nematodes and Ants

Answer 11

• nematodes live in bird poop, ant eats bird poop so now nematode in ant but birds don’t eat enough ants so how do nematodes fix this?
• makes ants look like abdomen look like the berries that birds like to eat and stick them up in the air to attract the ant
• nematodes are tricky motherfuckers

Question 12

Toxoplasmosis

Answer 12

• evolutonary advantage for the toxoplasma for mice to be eaten by cats so mice have to go near cats to be caught and eaten to transfer the parasite
• rats normally don’t go near cats, instead venture toward bunny smell
• if rats are infected with this they go toward what smells like cats
• if humans have this you want to hang out with cats? or nothing at all you can just have it?
• modifies proteins in host brain and even gene expression in brain

Question 13

Malaria

Answer 13

• struggle against this disease involves evolution and society
• two hosts
• male and female gametes of parasite get sucked up into mosquito and unite
• make oocysts that releases stuff
• next time mosquito bites it transmits these cell to the human host which grows in the human body
• which eventually infects red blood cells where the gametes are produced again and then sucked up by mosquitoes in a vicious cycle
• plasmodium parasites carried from mosquito to human and back from human to mosquito

Question 14

Natural Selection on Humans by a Parasite

Answer 14

• mutations in human populations that affect resistance to malaria
• sickle cell disease and other genetic diseases that affect blood cells can give resistance by blocking malaria parasite from reproducing in red blood cells
• mosquitos like the smell of people who are already infected

Question 15

Malaria Experiment

Answer 15

-more attracted to scents of malaria-infected
children than non-infected.
-infected children, mosquitoes were more attracted to \
-children with gametocyte-stage Plasmodium (infective) than with other (non-infective) stages of the parasite.
-“strongly suggests that gametocytes increase the attractiveness of the children to mosquitoes”

Question 16

Battling Malaria

Answer 16

• don’t target mosquito control to larvae or egg-laying young mosquitoes.
• develop “late-life-acting” insecticides that kill the older infectious mosquitoes – note that these would be targeted at disease control, not insect control; you would still get mosquito bites, but not malaria.

Question 17

Multicellular and Unicellular Dog

Answer 17

• single cell parasite arose few centuries ago within normal dog
• has own gene markers inherited from ancestor
• parasite passed from multicellular dog to multicellular dog where it forms a non lethal tumor
• tumor has ancestral genotype
• own genetic lineage and is obligate parasite
• distinct and novel form of dog
• passed as STD

Question 18

Mutulaism

Answer 18

• both species benefit

- gecko that pollinates flowers and gets protection in return