Ch9 Arms Races, Coevolution & Diversification

Question 1

Coevolution

Answer 1

a process of reciprocal adaptive change in two or more species over generations, caused by selection pressures that each party imposes on the other. Most often requires antagonistic selective pressures. Adaptation in one species reduces the fitness of another. Not always negative, sometime pollinators and flowers both benefit.

Question 2

Evolutionary Arms Races

Answer 2

an increase of adaptations and counter adaptations between two or more parties. Can occur within species or between species.
Symmetric - like both parties stockpiling weapons
Asymmetric - one party invest in offense, the other in defense
driving forces in generating morphological and behavioral diversity.

Question 3

Primary Defenses

Answer 3

operate before predatory attacks and reduce the likelihood of direct interactions

Question 4

Secondary defenses

Answer 4

operate during or after a predator has attacked and reduces the likelihood that prey will be captured

Question 5

Camouflage

Answer 5

warning signals and mimicry. Ex. Cuttlefish - many specializations that allow them to match any background by using visual information to guide their cognitive component.
Chameleons- will change their degree of matching based on their predators’ visual acuity. Matches better when birds are around vs snakes.

Question 6

Aposematism

Answer 6

many animals are dangerous, unpalatable, or toxic and convey this by having bright conspicuous warning colors. Predators avoid such prey due to learned avoidance.

Question 7

Startle

Answer 7

changes in appearance to scare away or confuse

Question 8

Bat/Insect Arms Race

Answer 8

moths became nocturnal to avoid predation from birds. Flying mammals develop echo localization to fill niches for nocturnal feeding. Some moths evolve elaborate tails which seem to confuse bats. Moths develop tympanic ears to detect bat calls. Echolocation call is prone to eavesdropping because it is very loud. Activation of a hearing circuit in moths because it causes evasive motor behavior (behavior is graded depending on stimulus). Evolution of massive ears to detect movement without echolocation. Some moths evolved a noise-producing organ they use to ‘jam’ the bat sonar. The organ may: startle the bar and jam its sonar (interferes with the determination of target distance). Announce its foul taste which deters bats from eating it.

Question 9

Avian Brood Parasites

Answer 9

egg laying and nest defense. 1st line of defense is not getting parasitized. Host- mobbing with acoustic and visual displays and physical attacks. Parasite - cuckoos evolved similar physical features to hawks to decrease the mobbing behavior of the host. A host can still reject an egg if it gets laid. The host learns their eggs and rejects nonmimetic eggs. Parasites evolve as egg mimics. A host that has greater egg rejection behavior requires a greater match. Once the host becomes very good at discrimination, cuckoos often abandon that host species. Cuckooos only match egg mimics as much as necessary, newly parasitized host species are often nondiscriminatory.
2 strategies
create a large level of egg polymorphism so the parasite has a hard time mimicking ( each egg has a different appearance). Parasite has to search several nests to ensure a match
Increase egg consistency and discrimination so mimic has to be much better at matching. Makes discrimination easier unless the mimic is perfect. Redinfed rejection because of low variability in egg color/ pattern