Download Community Ecology - Avon Community School Corporation

2.d.1 – All biological systems from cells and organisms to
populations, communities, and ecosystems are
affected by complex biotic and abiotic interactions
involving exchange of matter and free energy (54.1 54.5).
 2.e.3 – Timing and coordination of behavior are
regulated by various mechanisms and are important in
natural selection (54.1).
 4.a.5 – Communities are composed of populations of
organisms that interact in complex ways (54.1 & 54.2).

4.a.6 – Interactions among living systems and with their
environment result in the movement of matter and
energy (54.2).
 4.b.3 – Interactions between and within populations
influence patterns of species distribution and
abundance (54.1).
 4.c.4 – The diversity of species within an ecosystem may
influence the stability of the ecosystem (54.2).


The study of the interactions between
the species in an area
 Interaction between species
 May be positive, negative, or
 Ex:
1. Coevolution
2. Predation
3. Mimicry
4. Competition
5. Symbiosis
neutral


When two species
have reciprocal
evolution to each
other
Ex:
› Flowers and their
pollinators
 Predator
and
prey
relationships
 Ex – Lynx and
Hares
Often results in interesting defenses or
adaptations
 Ex:

› Plant defenses
› Cryptic coloration
› Aposematic coloration

A passive defense where the prey is
camouflaged against its environment
 The
use of
Poison Arrow frogs
conspicuous
colors in toxic
or unpalatable
organisms to
warn off
predators
Defense mechanism where the mimic
has a resemblance to another species,
the model
 Types:

› Batesian
› Mullerian

Palatable species mimics an
unpalatable model
Hawk moth larva
Snake

Two unpalatable species resemble each
other
Cuckoo Bee
Yellow Jacket
When two species rely on the same
limiting resource
 Intraspecific competition usually more
severe than Interspecific competition
 Why?

Predicts that two species with the same
requirement can not co-exist in the same
community
 One species will survive and the second
will go extinct

The n-hyperspace of requirements for a
species
 How a species “fits into” an ecosystem
 Species can not have niche overlap; the
Competitive Exclusion Principle

1. Fundamental - what a species is
theoretically capable of using
2. Realized - what a species can actually
use
A way that species avoid niche overlap
by splitting up the available resources
 Ex: Anolis lizards

A. distichus
A. insolitus
When two different species live together
in direct contact
 Types:

1. Parasitism
2. Commensalism
3. Mutualism
Parasite harms the host
 Parasites may be external or internal
 Well adapted parasites don't kill the host

 One
partner
benefits while
the other is
unchanged
 Ex. – Cattle
and Egrets
 Both
partners
benefit from
the interaction
 Ex: Pollinators
and flowers
Acacia Tree and Ants

A keystone species is
a plant or animal
that plays a unique
and crucial role in
the way an
ecosystem functions.
Without keystone
species, the
ecosystem would be
dramatically
different or cease to
exist altogether.

Prairie dogs are a
keystone species in
the Great Plains
region of the U.S. and
Canada

A keystone as an arch's crown secures the
other stones in place. Keystone species play
the same role in many ecological
communities by maintaining the structure and
integrity of the community.


often, but not
always, a predator
A keystone species'
disappearance
would start a domino
effect. Other species
in the habitat would
also disappear and
become extinct.
In terrestrial environments,
fire ants function as keystone
predators by suppressing the
numbers of individuals and
species of arthropods that
could be harmful to
agriculture.
 Changes
in
species
composition
over time
Sere: unstable stage usually replaced by
another community
 Climax: stable stage, self-reproducing

1. Primary
2. Secondary
Building a community from a lifeless area
 Ex: volcanic islands
glaciated areas
road cuts

 The
first example of primary
succession was worked out on
the Indiana Dunes
 Stages:
› Open Beach
› Beach Grasses
› Conifers (Junipers and Pines)
› Oaks
› Beech-Maple forest (Climax)
Where a community has been disturbed
and the soil is mostly intact
 Ex:

› Cutting down a forest
› Blow-outs on the Dunes
1. Autogenic Factors
2. Allogenic Factors
Changes introduced by the organisms
themselves
 Ex: toxins
acids

 Outside
disturbances
 Ex: Fire
Floods

If you understand the causes and
controlling factors of succession, you can
manipulate them

Study of the past and present
distributions of individual species and
communities
1. Lack of dispersion
2. Failure to survive in new areas
3. Retraction from former range area
Fossil Evidence
 Pollen Studies
 Transplant Experiments

Special cases in Biogeography
 Must be colonized from other areas

Island size
 Distance from mainland

Small islands hold few species
 Why?
 Fewer niches available for species to
occupy

Closer islands have more species
 Why?
 Easier for colonization

Islands tend to have high numbers of
Endemic species
 Why?
 Adaptive Radiation and Evolution of
new species

Identify various types of interspecific interactions.
 Identify the Competitive Exclusion Principle and the
concept of the Ecological Niche.
 Recognize species with a large impact.
 Identify the differences between Primary and
Secondary Succession and the causes of
succession.
 Recognize some biogeographical aspects of
community diversity.
