QOTD

•What is a predator?

PREDATION and PARASITISMMr.Dunnum

CONSUMPTION

• The consuming of one living thing by another.•A basic eating relationship between

populations of different species.•Must be evaluated on the basis of its

effects on populations, not on individuals.

MAJOR TYPES OF CONSUMPTION• Herbivory --- Eating of plants by animals. May not

result in death of individual plant.• Parasitoidism --- Larvae of parasitoids consume hosts.• Cannibalism --- The eater and eaten belong to the

same species (intraspecific predation).• Parasitism --- Host provides nutrition to one or many

individual parasites. Host may or may not die.• Predation --- Predator kills prey and consumes all or

part.

PARASITOIDISM

• Insects, usually flies and small wasps, that lay their eggs on living hosts. The larvae then feed within the body of the host, eventually causing death.•Recent experimental evidence suggests

that parasitoids locate their hosts by responding to airborne chemical signals from plants damaged by the host.

PARASITOIDS

• A tachinid fly lays eggs on a hornworm (moth larva). The fly larvae develop by consuming the hornworm.• Many species of

ichneumon wasps are parasitoids.

CANNIBALISM

• An individual consumes another individual of the same species.• A form of intraspecific predation.• Relatively common among insects when density

is high. Usually involves adults consuming eggs and larvae.• Demonstrated to be density-dependent factor

regulating experimental insect populations.

PARASITISM

•Occurs when a member of one species (parasite) consumes tissues or nutrients of another species (host).•Parasites live on or in their hosts;

often for long periods of time.•Parasites are most often much

smaller than their hosts.• It is not necessarily fatal to the host.

A VERTEBRATE PARASITE

• The sea lamprey was introduced into the Great Lakes in 1921 through the Welland Canal.• Contributed greatly to the

decline of whitefish and lake trout (shown).• Chemical control

programs started in 1956 have reduced lamprey populations.

INVERTEBRATE PARASITES

• Tapeworm is an intestinal parasite in many species of vertebrates, including humans.• The deer tick (small

one) and wood tick are common external parasites on mammals.

VIRAL PARASITES

• The common influenza virus (top) has inhabited every host in this room! It has caused more deaths than any other pathogen.• The bird flu virus (bottom)

is a potential threat to humans.

PREDATION

• The most conspicuous interaction is when an individual of one species (predator) eats all or most of an individual of another species (prey).• The most thoroughly studied consumptive

relationship between species.• Of high ecological and evolutionary significance.• An everyday occurrence in nature.

Possible Outcomes of Predation• 1. Predator population has little effect

on abundance of prey population.•2. Predator population eradicates

prey population; this may contribute to extinction of predator population due to lack of food.•3. Predator and prey populations

coexist in dynamic equilibrium.

Description of Dynamic Equilibrium• When predator numbers are low, prey numbers increase

rapidly.• As prey numbers increase, predators begin to increase.• When predators numbers are high, prey numbers decrease

rapidly.• As prey numbers decrease, predator numbers fall.

The Hare & Lynx Predator/Prey Relationship

• Snowshoe hare and Canadian lynx show classic population cycles with a 10-11 year periodicity.• Hare are herbivores and

feed on twigs under the snow in winter; lynx feed primarily on snowshoe hare.

Moose and Wolf of Isle Royale

• The world’s longest running predator/prey research project. The 47th year of wolf and moose monitoring was completed in the winter of 2006.

• Winter provides the best opportunities for aerial surveying of the wolf and moose populations, with leaves off the trees and snow on the ground.

Predators as Agents of Biocontrol

• Predators have been used in attempts to control a variety of plant and animal pests. Often called: biocontrol.• Ladybird beetles and

ant lions (lacewing larvae) have been used.

Parasites as Agents of Biocontrol

• European rabbits were introduced into Australia in 1859 and became a major pest.

• In late 1950, the myxoma virus, spread by mosquitoes, began killing rabbits in large numbers. By 1953, rabbit immunity was detected. Today, the virus may kill only 50 % of the rabbit population during an epidemic.

• Another virus (calicivirus), native to China, was found and testing as a potential biocontrol agent began in 1995 and continues to the present.