Lecture 17

Question 1

What are some costs to signalling?

Answer 1

1. physiological

drain on resources during growth (often case for visual signals, like feathers or organs for bioluminescence) or during immediate production of signals (movement or making sounds & vibrations)

2. exploitation (eavesdropping)

signals (or cues) may be intercepted by an unintended receiver (predator or parasite)

may be a competitor or natural enemy

Question 2

What are social alarm pheromones?

Answer 2

chemicals that elicit particular behaviours amongst the individuals within a colony

displaying ants release an alarm pheromone that recruits other ants

spiders easily capture displaying ants

Question 3

Example of eavesdropping interspecific cues

Answer 3

butterflies are attracted to ants, but so too are spiders
spiders can capture the butterflies that are flying around

Question 4

Why is camouflage important?

Answer 4

reduces the likelihood that an organism will be detected or recognized

Question 5

What is maquerade?

Answer 5

a type of camouflage that prevents recognition by resembling an uninteresting or unimportant object, like a leaf or a stick

Question 6

Motion masquerade

Answer 6

movement improves crypsis and thus reduces likelihood of predation (e.g. stick insect on a branch should move asw)

individuals will start swaying when they detect changes in wind pressure

Question 7

Mimicry – masterpiece of evolution

Answer 7

1. benign Batesian mimic resembles a noxious or dangerous model

• predators avoid eating both the model and mimic

2. aggressive mimicry - e.g. frogfish have a ‘lure’ that attracts prey (Fish) by mimicking worms, small shrimps, or fish. The prey approaches the lure and is swallowed up by the frogfish
3. Mullerian mimicry - 2 or more species have similarly anti-predator traits (e.g. are distasteful) and similar ‘warning’ signals, but do not share an immediate common ancestor

Question 8

coevolution

Answer 8

a process involving pairs of species (or lineages) whereby changes in the traits of individuals of one species (or lineage) causes reciprocal changes in the other species (or lineage) over evolutionary time

e.g. cheetahs are really fast, deer are really fast and evolve to be faster to escape cheetahs, cheetahs evolve to be faster, etc.

Question 9

Antagonistic interactions. . .

Answer 9

may lead to reciprocal evolutionary change and ‘arms races’ : while both predator and prey improve their offensive and defensive adaptations, there is little change in their net advantage

Question 10

Prey defense adaptations and predator counter-adaptations

Answer 10

camouflage – improve sensory acuity (learning, sensory organs)

mimicry – improve sensory acuity

early detection of predator – camouflage, faster or more secretive approach

active defense (chemical, physical) – capacity to de-activate or detoxify the chemical defense

Question 11

Brood parasites

Answer 11

• where a female of 1 species lays her effs in the nests of other species who raise the ‘parasitic’ chick
• brood parasite avoids the ‘costs’ of raising chicks, while the cost to the host includes an energetically costly loss of reproductive output
• classic example of coevolution in the context of sensory info

SELECTION ON HOST TO DETECT BROOD PARASITE

SELECTION OF CUCKOO TO AVOID BEING DETECTED