Chapter 2: Living Things in Ecosystems
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2.2 How Species Interact with each other
 Ecosystems are made up of biotic and abiotic components
 The biotic components – organisms – affect one another
 The five major types of interactions are: predation, competition, parasitism, mutualism and
commensalism
Predation
 In predation, one organism kills and eats another organism
 The organism that is eaten is called the prey
 The organism doing the eating is called the predator
 Examples: lions feeding on zebras; cougars eating deer; snakes consuming mice; birds eating insects;
blue whale feeding on tiny krill
 Predators tend to feed on young and weak individuals; as prey decline, predators either feed on other
organisms or die
Competition
 Competition occurs when two or more organisms of the same or different species attempt to use the
same limited resource
 Examples: Lions and hyenas fighting over the same carcass; two plants fighting for a limited amount of
sunlight
 Species can fight over the same resource and never see one another, ex: one insect feeding on a
certain plant during the day and another who feeds on that same plant during the night; because they
use the same food source, the two species are competitors
Parasitism
 Parasites are organisms that live in or on another organism and feed on it without immediately killing
it; parasitism is the relationship between the parasite and its host
 Examples: ticks, fleas, tapeworms, viruses, blood-sucking leeches, mistletoe
 Organism the parasite takes nourishment from is known as the host
 The difference between parasitism and competition is that the parasite does not immediately kill their
host; it lives in or on the host most of its life; and the parasite weakens its host making it more
vulnerable for predators
Mutualism
 Mutualism is the cooperative partnership between two species in which both species benefit
 Examples: clownfish and the sea anemone; bacteria in your intestines; acacia tree covered in ants in
Central America (when the ants were removed, the tree suffered)
Commensalism
 Commensalism is the rarest and strangest type of species interaction
 It is the relationship in which one species benefits and the other is neither harmed or helped
 Example: sharks and remoras