Download Interactions Between Organisms - mvhs

Community Ecology
Relationships Between Organisms
AP Biology
Ecological Niches
• A species' niche includes:
• Habitat - where it lives in the ecosystem
• Relationships - all interactions with other
species in the ecosystem
• Nutrition - its method of obtaining food
Competition
• Competition = when two species compete
for the same resource
• Competition can lead to competitive
exclusion or resource partitioning
Competitive Exclusion
• Competitive Exclusion
Theory
– 2 species cannot occupy the
same niche
– If 2 species occupy the same
niche, then they will compete
until one eliminates the other
(becomes extinct)
Resource Partitioning
• If one species’ niche is
modified through
natural selection, then
it will be able to
coexist with the other
species (that it
competed with before).
– niche differentiation
– Modified use of
resources
Character Displacement
• Is evidence of previous competition
between species
• Allopatric Speciation = speciation that
occurs in species that are geographically
isolated from each other
• Sympatric Speciation = speciation that
occurs in species that live in the same area
Character displacement
• How does the diagram
show evidence of
competition?
• When the populations
live together, character
displacement occurs in
order for the
populations to co-exist
(sympatric speciation)
Animal Defenses: Aposematic coloring
Coloring or
markings to
warn off
predators
Animal Defenses : Cryptic coloration
Coloring that
disguises an
animal’s shape
Animal Defenses: Batesian Mimicry
A species mimics a successful species but lacks
the actual attribute– “pretending to be harmful”
harmful
Not
harmful
Scarlet king snake
Müllerian Mimicry
A species resembles another successful (harmful)
species and shares the attribute (is also harmful)
Monarch butterfly
Viceroy butterfly
Plant Defenses Against Herbivory
• Thorns and spines
• Glandular hairs
– store and secrete toxins
• Deposition of crystals in plant tissues
– makes tissues tougher
• Chemical compounds
– May be distasteful or toxic to animals
– May cause abnormal development in animals
Images taken without permission fron http://www.ext.vt.edu/news/periodicals/cses/1998-02/Glandular_hair_leaf_72dpi.JPG and
http://fm2.fieldmuseum.org/plantguides/jpgs/LOGA-stry-toxi-pan-2735.jpg
Summary of Species-Species Interactions
Competition
-/-
Predation
+/-
Herbivory
+/-
Parasitism
+/-
Disease (Pathogen)
+/-
Mutualism
+/+
Commensalism
+/0
Keystone Species
• species that has a strong influence on its
ecosystem.
– Ex. Sea otters, prairie dogs
• If it is not there  will cause populations
of other species in the ecosystem to go
down or become extinct;
• Can drastically change the ecosystem even
though it isn’t the most abundant species.
– Dominant species = most abundant species
Images taken without permission from http://animal.discovery.com/mammals/prairie-dog/ and
http://carinbondar.com/2010/11/this-weeks-cool-biology-job-sea-otter-population-ecologist/