lecture 13 - defensive strategies Flashcards
biotic vs abiotic threats
biotic:
- between same species or different
- living
- predators etc
abiotic:
- threat of wave action
- changes in temp or salinity
- things not from organisms
predation as a major selective force
- Almost all organisms have predators
- Predators have a dramatic impact on fitness (no gene passing if dead)
- Predators rarely 100% successful
biotic vs abiotic defensive strategies
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
predation as major selective force
- what makes predation a major selective force?
- 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
red queen hypothesis
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
why is there asymmetry in strength of selection on predators & prey ?
- 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
chart w phases of predatory act & selected defenses
- what are the phases of predation and explain them
search & detection
- self-explanatory
pursuit
subjugation (subdue)
- collected and eaten
selected defenses against SEARCH & DETECTION phase of predation
camouflage (crypsis)
mimicry
hiding
activity patterns
- like DVM (of bobtail squid or zoop)
selected defenses against PURSUIT phase of predation
Fast swimming/running
escape behaviours
- like tail flipping in lobsters
selected defenses against SUBJUGATION phase of predation
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
induced defenses - definition and explanation
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)
components of gastropod shell
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)
ways of being crushed
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
gastropod shell defenses against crushing predators
- 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
study done on tubercles (spines) - Palmer et al
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: