lecture 13 - defensive strategies Flashcards

1
Q

biotic vs abiotic threats

A

biotic:
- between same species or different
- living
- predators etc

abiotic:
- threat of wave action
- changes in temp or salinity
- things not from organisms

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2
Q

predation as a major selective force

A
  • Almost all organisms have predators
  • Predators have a dramatic impact on fitness (no gene passing if dead)
  • Predators rarely 100% successful
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3
Q

biotic vs abiotic defensive strategies

A

biotic: coming from same (conspecific) or different species (predation) –> competition for space, resources, predation)

abiotic:
- threats of save action, change in salinity, etc
- NOT from organism

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4
Q

predation as major selective force
- what makes predation a major selective force?

A
  • almost all organisms have predators
  • predators have dramatic impact on fitness (if prey dies, no genetic material passed on)
  • predators rarely 100% successful –> the traits of the ones that survive will be passed on to future generations
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5
Q

red queen hypothesis

A

definition: Prey and predators must continuously improve in performance just to survive over the long term

P-P interactions (predator/prey)

predator prey interactions are reciprocal and dynamic
– both organisms influencing selective environment of one another

arms race

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6
Q

why is there asymmetry in strength of selection on predators & prey ?

A
  • predator loses: simply misses dinner
  • prey loses: loses life

asymmetry in selective force —> a lot more at stake for prey vs predator

  • predator just doesnt get dinner, whereas prey loses life — natural asymmetry
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7
Q

chart w phases of predatory act & selected defenses
- what are the phases of predation and explain them

A

search & detection
- self-explanatory

pursuit

subjugation (subdue)
- collected and eaten

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8
Q

selected defenses against SEARCH & DETECTION phase of predation

A

camouflage (crypsis)

mimicry

hiding

activity patterns
- like DVM (of bobtail squid or zoop)

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9
Q

selected defenses against PURSUIT phase of predation

A

Fast swimming/running

escape behaviours
- like tail flipping in lobsters

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10
Q

selected defenses against SUBJUGATION phase of predation

A

armour
- like crab or gastropod shells

retaliation
- fighting back

toxicity

autonomy
- dropping a limb to distract

structural add ons
- creation of long spines –> such as zoop, where too big for predator

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11
Q

induced defenses - definition and explanation

A

when organisms only have a defense mechanism at certain times - NOT always

induced by presence of predators - will stop growth etc to develop the defenses

can be combo of multiple different types (* Structural *Chemical
* Behavioural)

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12
Q

components of gastropod shell

A

protoconch
- first part of shell developed in larval stage

whorl
- a cavity formed by calcium carbonate – laid down around central matrix

spire
- consists of all of the previously laid down whorls

body whorl
- most recently laid down
–> has aperture and apertural lip (outer lip of shell aperture)

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13
Q

ways of being crushed

A

Apertural Lip Crush

Spire Crush
- small part in dactyle –> which is closer to condyle = more force to be crushed as the length output of lever arm is shorter (force advantage)

Apertural Lip Peel
- open like a can opener

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14
Q

gastropod shell defenses against crushing predators

A
  • Overall thickening of shell
  • Thickened apertural lip
  • Apertural teeth
    - waves where shell opening - adds thickness where can break
  • Narrowed aperture
    - less likely to get cheliped in and pry open
  • Reduced spire
    - if less pointy up top, less close to condyle (pivot point) - predator less
    advantage to crushing
  • Thickened tubercles & varices
    - projections like spikes
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15
Q

study done on tubercles (spines) - Palmer et al

A

tubercles are spines on gastropod shells

a porcupine fish preys on gastropods and has teeth that crush them

study done on 2 species of porcupine fish and 2 species of gastropods

3 things found looking at Effect of tubercles on crushing attempts:

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16
Q

Palmer et al study

3 things found looking at Effect of tubercles on crushing attempts:

A

1) tubercles increase effective diameter
- reduce force advantage of jaws
- shell doesnt get as close to condyle (as far in mouth) so less force can be applied

2) tubercles allow the force to be distributed over a greater area (reduces stress on shell)

3) tubercles allow for the crusher to have less access to area, and the spines can damage predator
- this might be most important

17
Q

further findings of Palmer et al in relation to size of shell

A

tubercles allowed for the critical size of the shell to be smaller on average

a gastropod species w strong spines could have a smaller size overall, whereas the species with weak spines would require a larger shell to reach critical size

with weaker spines, the gastropod has to put in more energy and resources to growing to a larger size, w strong spines, need less size bc of these

18
Q

further study on tubercles (modification of shells)

A

filed off tubercles of shells and others had spines

the critical length of those with spines removed was needed to be larger than those with spines

19
Q

presence of spines on gastropods in different latitudes

A
20
Q

Number of fish families & species that crush molluscs
Tropical vs. Temperate

A

found high correlation between species that crush and tropical latitudes (68%)

temperate:
proportion of species crushers = 29%

21
Q

study showing evidence of convergence - gastropod shell defences

A

Lake Tanganyika - Tanzania

this freshwater system gastropods w really thick shells - normally thin shells in freshwater bc lack of calcium carbonate

when looking at presence of predators –> much higher here bc crab chelipeds are larger therefore have greater force

indepedently evolving to have thicker shells in different locations to protect themselves from shell crushing predators = CONVERGENCE

22
Q

Defensive value of gastropod operculum?

A

example of Taylors sculpin
- suction feeder
- preys on gastropods
- has pegs arising from neurocranium which puts holes in gastropods

40% of unpunched gastropod shells survived completely through fish and out of feces

23
Q
A