A little bit about myself • Hi my name is Sean Edgar.• Today I hope will be usefulfor both you and me.• Don’t be afraid to ask meabout something you’reunsure of.• You’ll have theopportunity to ask mequestions at the end of thepresentation.• Enjoy the ride! (she sai-
Predators• A predator is an animal or organism that huntsand kills other organisms for food in an actcalled predation.• A predator may consume all or part of anotherorganism through a process known as “eating.”• Definition is very broad.• Encompasses three main groups of organism;• Classic or “true” predators : most commonlythought of predators including, sharks,cheetahs, bears etc.• These predators kill their prey soon aftercatching it, normally consuming it all.• Grazers: can be considered a predator by thesame definition but consume only part of a preyorganism.• Parasitic species’: live on or inside a preyorganism or “host.” They may be deemedpredators as they too will obtain an energysupply by consuming part of a prey organism,albeit a microscopic level of consumption.
Figure 1.339.284.1: Polar bears resting after eating a walrus probably.
The importance of predators• Although predators may sometimes be tarredwith the “bad guys” reputation, they in fact playan important role in regulating preypopulations.• Predator-prey interactions are cyclical. ierepeated increase and decrease.• Reason?• The prey in this case, rabbits, initially rapidlyincrease in numbers due to a plentiful supply ofenergy from the previous trophic level tosupport their growth.• As their numbers increase the predator, thefoxes numbers’ also increase, with more rabbitsavailable as food.• This causes a subsequent decrease in the rabbitpopulation, which too effects a decrease in thenumber of foxes allowing the pattern to repeat.• Thus, both predator and prey are linked.
The importance of predators: revisited• Not only do predators curb prey populations fromspiralling out of control, but they have also beenshown to maintain species biodiversity.• Let me give you an example:In the 1960s an experiment was done by RobertPaine in a community of invertebrates inhabitingareas within the intertidal zone in the northwestof the pacific ocean. (The intertidal zone is theregion of seashore between the water mark athigh and low tides.) The top predator in thiscommunity is a starfish which feeds on mussels,barnacles and other invertebrates. When thestarfish were removed, a species of barnacle andmussel began to outcompete the other speciesand eventually came to occupy almost all availablespace. The species diversity decreased from 15 to8. By keeping the numbers of the more successfulcompetitors in check, the starfish maintained adiversity of species. When they were removed,the biodiversity of species declined.
A closer look at prey organisms• While I have talked about predator organisms, itis also important to consider types of prey.• As a predator is an animal that hunts and catchesits food, prey are the organisms to which theformer definition refers to being caught.• Examples may include small mammals such asrabbits, mice etc.• Over time, predators and prey alike have evolvedin ways to make them more successful atcatching and avoiding being caught respectively.• For predators these adaptations may be; claws,fangs, stingers or poisons.• However it is far better to be the hunter ratherthan the hunted, and so the adaptations ofpreyed animals have to be more sophisticated ifthey are to survive.Figure 1.85792: “Hey there.”
Camouflage etc• Camouflage is a passive defence mechanism usedby some preyed organisms.• It allows the prey to merge into its background,making it difficult for predators to spot them,especially if they have poor eyesight.• When camouflaged the animal only needs to staystill until they have avoided detection and thedanger has passed.• Another mechanism of camouflage is shapewhere the organism will change shape to blend inwith the shapes of its surrounding environment.Can you spot the stonefish?!!
Warning colourations• Many animals and organisms use brightlycoloured markings and patterns on the surface oftheir body.• This advertises the fact that they may beunpleasant or poisonous to eat or merely sendinga warning to a possible predator to “stay clear.”( a bit like how a man might get tattoos toadvertise how tough he is!!)But not really.• This type of colouration is known as aposematiccolouration.• Predators will therefore have to exercise cautionshould they choose to eat this type of prey as itcould potentially cause harm to them.Figure 1.1,000,002: “Don’t eat me. I’m well hard.”
Mimicry etc• Prey organisms may successfully avoid being caughtand eaten by a predator through mimicry.• This involves the prey organism mimicking as best itcan the behaviour of another usually harmfulspecies so as to discourage the predator fromattacking.• There are two types of mimicry; Batesian andMullerian.• In Batesian mimicry, an edible or harmless speciesmimics a poisonous or harmful one. An example ofthis is the yellow and black colour patterns of theharmless hoverfly, similar to the harmful wasp.• In Mullerian mimicry, two or more inedible orpoisonous species have evolved to have the same orsimilar warning signals. Presumably in this way eachspecies gains an additional advantage because oncea predator has learned to avoid a particular warningsignal or colouration with which it first cam intocontact, it would then be sensible of the predator toavoid all other similarly patterned species. Forexample, the caterpillars of the cinnabar moths.
ConclusionTopics discussed:• Types of predator• Importance of predators• Types of prey• Adaptations of predators and prey, inparticular:• Camouflage• Warning Colourations• Mimicry
Thanks for listening etcI’ll now be happy to take any questions you may have