This document summarizes the five major types of species interactions: predation, competition, parasitism, mutualism, and commensalism. It defines each interaction and provides examples. Predation involves one species consuming another for food, while competition occurs when two species require the same limited resources. Parasitism benefits one species at the expense of the other. Mutualism is a cooperative relationship that benefits both species, such as pollination. In commensalism, one species benefits while the other is not affected.

1. COM
M
UNITY ECOLOGY:
SPECIES
INTERACTIONS
TEXTBOOK: CHAPTER
20, SECTION
1
(PP. 399-404)

2. SPECIES INTERACTIONS
Community: all the interacting organisms in
one area (ecosystem)
Within a community, there are
5 Major Types of Species Interactions:
 1) Predation 3) Parasitism*
 2) Competition 4) Mutualism*
3) Commensalism*
*Symbiosis: a close, long-term relationship
between organisms of two species

3. PREDATION
Predation = A relationship in which an individual of
one species eats all or part of an individual of
another species.
Predator: captures, kills, and consumes another
organism
Carnivores
Herbivores
Ominvores
Prey: organism being
consumed

5. Predatory Adaptations
include: venom, fangs,
claws, speed, camouflage
PREDATOR-PREY ADAPTATIONS
Prey Adaptations
include: speed,
camouflage,
poisons, thorns,
mimicry

6. Mimicry: a defense in which one organism resembles
another
Two types of
mimicry:

7. AP Biology
What kind of mimicry?
Coral snake
is poisonous
King snake is not
Red on yellow, poison fellow;
red on black, safe from attack

8. 2) COMPETITION
Happens when two or more species use the
same resources
Competition results because resources are
often limited
Competition drives two key processes:
1. Competitive Exclusion
2. Character Displacement

9. *when one species
is eliminated due
to competition
-No two
similar species can
occupy the same
niche
= Reduced
Niche Size!
*Favors specialists
COMPETITIVE EXCLUSION

10. AP Biology
Character Displacement
The evolution of anatomical differences to
reduce competition
 i.e.: Darwin’s finches evolved specialized beaks

11. SYMBIOSIS
• Non-feeding, non-competitive relationships
• Long-term
• Interspecific
• Three types:
1. Parasitism
2. Mutualism
3. Commensalism

12. 3) PARASITISM
Parasitism: an interaction in which one
individual is harmed and the other benefits
Parasite: feeds on another individual (the
“Host”)

13. 4) MUTUALISM
Mutualism: a cooperative
relationship in which both
species benefit
• Many unusual behaviors such as cleaning
behaviors
• Pollination is an important mutualistic
relationship

14. 5) COMMENSALISM
Commensalism: a
relationship in which
one species benefits
and the other is not
affected