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
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
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
Predation is a powerful force in a community.
The relationship between predatory and prey influences the size of each population and affects where and how each species lives.
Many types of organisms can act as predators and/or prey.
All heterotrophs are either predators or parasites or both.
Predator Adaptations
Natural selection favors the evolution of predator adaptations for finding, capturing, and consuming prey.
Ex: Rattlesnake adaptations to help detect prey
*acute sense of smell
*heat-sensing pits located below each nostril
Other examples
*Venom – to disable or kill prey
*sticky spider webs to catch prey
*Flesh-cutting teeth
*speed of cheetahs
*striped patter of tigers
*cutting and chewing mouthparts (herbivores)
Prey Adaptations
*A prey’s survival depends on its ability to avoid being captured/eaten.
*Natural selection favors adaptations in prey that allow the prey to escape, avoid, or otherwise ward off predators.
Animal Prey Adaptations
Fleeing, hiding, resembling an inedible object, deceptive markings, chemical defenses, mimicry (predators avoid similar-looking individuals)
Plant Prey Adaptations
*Plants cannot run away from a predator
Physical defenses: thorns, spines, sticky hairs, tough leaves
Chemical defenses: poisons, irritants (poison ivy/oak), bad-tastes
*chemical defenses are often byproducts of the plants’ metabolism (called secondary compounds)
ex: strychnine, nicotine
Resource partitioning among Dominican Republic lizards. Seven species of Anolis lizards live in close proximity, and all feed on insects and other small arthropods. However, competition for food is reduced because each lizard species has a different perch, thus occupying a distinct niche.
Sympatric species often partition available resources, reducing competition between them.
Analogy: Grocery store – items are on specified shelves, lined up in rows and columns (up and down the shelves) with tags marking their positions
Analogy – Utensils in your house are each used for a specific task in the kitchen/while eating