6.1 Relationships in the Ecosystem

Predators and Prey

• Predator= A consumer that actively hunts other living organisms.

• Prey= The organism that a predator eats.

Lynx and Snowshoe Hare

• Predator and prey population sizes are closely linked.

• A large prey population can support more predators than a small prey population.

Graph of Lynx and Hare• The changing population size of the prey

species controls the population size of the predator species.

Parasitism

• Parasitism= Is a relationship in which one organism feeds on the tissues or body fluids of another.

• Host= The organism on which a parasite feeds.• Parasites are a density-dependent limiting factor because

parasites are more successful in dense host populations.

Human Parasites

Symbiosis

• Symbiosis= Any relationship in which two species live closely together.

• 2 types: Commensalism and Mutualism

Commensalism• Is a symbiotic relationship that benefits one

species and neither helps nor harms the other.

Mutualism• A symbiotic relationship in which both

species benefit.

Review• What is a parasite? Provide an example of two

human parasites.• Why are herbivores not considered to be

parasites?• Explain symbiosis and the two different

symbiotic relationships.