Interactions

Predation

• The capturing of prey as a means of maintaining life– One organism benefits

– One organism is killed

Competition

• A rivalry between organisms for the same resources; The fitness of one of the organisms is lowered by the presence of another.

Competition

–Limited supply of at least one resourceused by both organisms is required

• Example: Animals compete for food, mating, or territory and plants can compete for water, food, minerals, sunlight.

Symbiotic Relationships

• Symbiotic Relationships – Interactions between two or more organisms; Two different species start a relationship (interact) in order to ensure survival

Symbiotic Relationships

– Symbiotic relationships include:

1. mutualism

2. parasitism

3. commensalism

Parasitism

One organism (the parasite) benefits

and the other (the host) is harmed, but is

still alive

A tomato

hornworm is

covered with

cocoons of

pupating

braconid

wasps

Parasitism

• Parasites take, but give no benefit back to their hosts.

• Examples – Tick and a dog, mosquitos and humans, bacterial infections such as a sore throat, amoebic dysentery (protist infection), viruses (flu)

Lampreys are Parasites

Parasitism

• Can be considered a special case of predation

• Because the parasite needs the host to remain alive, it is typically advantageous for the parasite NOT to kill its host

Mutualism

• Mutualism is any relationship between two species of organisms that benefits both species.

Examples of Mutualism

1. Pollination

2. Seed Dispersal

3. Lichens

Commensalism

• Relationship between two species where one species benefits from the relationship and the second species is unaffected

Examples of Commensalism

• Barnacles and Anemones

Interactions Summary

Type of Interaction Organism 1 Organism 2

Predation

Competition

Parasitism

Mutualism

Commensalism

Is Killed

“It’s Mutual”;

Both Benefit

Fitness is

Lowered

Harmed, but

Still Alive

One Benefits &

One is Unaffected