Download Relationships in Ecosystems-predators

Relationships
in Ecosystems
Types of ecological interactions
predation
parasitism
competition
mutualism
commensalism
symbiosis
Competition – two species share a requirement for a
limited resource  reduces fitness of one or both species
Predation – one species feeds on another  enhances
fitness of predator but reduces fitness of prey
herbivory is a form of
predation
Parasitism – one species feeds on another  enhances
fitness of parasite but reduces fitness of host
Mutualism – two species provide resources or services
to each other  enhances fitness of both species
Commensalism – one species receives a benefit from
another species  enhances fitness of one species; no
effect on fitness of the other species
Symbiosis – two species live together  can include
parasitism, mutualism, and commensalism
Predator-prey relationships
Predation is a straight-forward interspecies population interaction. One
species uses another as a food resource. Predators play an important
role in controlling prey population numbers in some systems. In simple
systems, the predator-prey relationship results in coupled population
osscilations
Classic example of predator-prey dynamics:
Canadian lynx & snowshoe hare
Coupled oscillation
• prey numbers increase, predator numbers increase…to a point where the
predation causes population decline in the prey item..
• Idealized predator-prey coupled dynamics.
•It is important to note that in most systems the food web- the web of
interactions among species- is far more complex than just a single
predator and single prey item. The relationships can become quite
complex and the “coupled” nature of the interaction becomes much
more vague.
Tactics of the Predator
1) Invisibility Cloak (cryptic coloration/ camouflage)
http://www.youtube.com/watch?v=__XA6B41SQQ
Tactics of the Predator
2) Patience is a Virtue (Hide and Wait)
Tactics of the Predator
3) Death by Poisoning (Venoms)
Tactics of the Predator
4) “Right this Way Please”: trap-doors, nets, and other deadly devices.
Tactics of the Predator
5) Bigger, Badder, Faster
200 mph
700 lbs & built to kill
What immortal hand or eye
Could frame thy fearful symmetry?
William Blake
http://www.youtube.com/watch?v=DWsN63PRCW8
17,000 lbs, and perhaps as smart as you
Tactics of the Predator
Combinations- Invisibility Cloak; Patience; Bigger, Badder, Faster
www.cheetah.org
Responses of the Prey
1) Invisibility Cloak (cryptic coloration/ camouflage)
Responses of the Prey
2) FLEE!!!!
Responses of the Prey
3) Eat me and die (poisons and aposematic coloration):
Responses of the Prey
4) “Shields up”: (armor):
Responses of the Prey
5) “Who wants fetid flesh for dinner? Surely not a proud
hunter like yourself” (play dead):
Responses of the Prey
6) Mimicry:
Batesian mimicry- looks like a toxic model- but is non-toxic
Mullerian mimicry- looks like a toxic model- AND is toxic
Responses of the Prey
6) Disguise:
Responses of the Prey
6) Strength in Numbers:
Herbivory, a special case of predation…
Not really- herbivory involves the taking of plant
material by an animal herbivore- is almost always
non-fatal, and can sometimes be an advantage
for the plant- or at least stimulate growth and
promote community diversity...
Herbivory generally becomes a problem when the
ecological system is out of balance.
E.g., invasive insects (gypsy moth)- or the loss of
predators (white-tailed deer)
Herbivore-plant relationships also can evolve into an “arms race”
Plants evolve armor (thorns, spines, prickles), toxicity, implant cells with silica,
and sometimes symbiotic relationships to defend foliage.
Plants evolve thorns, animals evolve morphology and behavioral techniques to
avoid thorns. Plants get taller, change canopy structure, animals get taller.
Plants trick animals into doing their bidding:
Plants want some parts eaten (fruits) for seed dispersal, only after the seed has
matured (thus ripening), and plants do not want foliage eaten…
The expense of herbivore defense is only worth it if the foliage is very valuable.
Plants that live it harsh conditions, can’t afford to rebuild foliage, so develop defenses.
Plants that grow in lush conditions, simply outgrow herbivores.
Predator-prey relationships