Essential Knowledge 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).
Essential Knowledge 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).
Community Ecology The study of the interactions between
the species in an area
Interspecific Interactions
Interaction between species May be positive, negative, or neutral Ex:
1. Coevolution2. Predation3. Mimicry4. Competition5. Symbiosis
Coevolution When two species
have reciprocal evolution to each other
Ex: › Flowers and their
pollinators
Predation (+/-) Predator and
prey relationships
Ex – Lynx and Hares
Predation Often results in interesting defenses or
adaptations Ex:
› Plant defenses› Cryptic coloration› Aposematic coloration
Cryptic Coloration A passive defense where the prey is
camouflaged against its environment
Aposematic Coloration
The use of conspicuous colors in toxic or unpalatable organisms to warn off predators
Poison Arrow frogs
Mimicry Defense mechanism where the mimic
has a resemblance to another species, the model
Types:› Batesian› Mullerian
Batesian Mimicry Palatable species mimics an
unpalatable model
Hawk moth larva Snake
Mullerian Mimicry Two unpalatable species resemble each
other
Cuckoo Bee Yellow Jacket
Competition When two species rely on the same
limiting resource Intraspecific competition usually more
severe than Interspecific competition Why?
Competitive Exclusion Principle
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
Ecological Niche 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
Niche Types1. Fundamental - what a species is
theoretically capable of using2. Realized - what a species can actually
use
Resource Partitioning A way that species avoid niche overlap
by splitting up the available resources Ex: Anolis lizards
A. distichus A. insolitus
Symbiosis When two different species live
together in direct contact Types:
1. Parasitism2. Commensalism3. Mutualism
Parasitism (+/-) Parasite harms the host Parasites may be external or internal Well adapted parasites don't kill the
host
Parasitic behavior: A female Nasonia vitripennis laying a clutch of eggs into the pupa of a blowfly (Phormia regina)
Commensalism (+/o) One partner
benefits while the other is unchanged
Ex. – Cattle and Egrets
Mutualism (+/+) Both partners
benefit from the interaction
Ex: Pollinators and flowers
Acacia Tree and Ants
Keystone species p. 1204 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
Prairie dogs are a keystone species in the Great Plains region of the U.S. and Canada.
Keystone species 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.
Keystone species 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.
Succession Changes in
species composition over time
Succession Stages Sere: unstable stage usually replaced
by another community rock lichen moss grass shrub
tree forest Climax: stable stage, self-reproducing
Succession Types1. Primary2. Secondary
Primary Succession Building a community from a lifeless
area Ex: volcanic islands
glaciated areas road cuts
Glacier Bay, Alaska Example of primary succession (p.
1209)Glacial retreat
Comment
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)
Secondary Succession Where a community has been
disturbed and the soil is mostly intact Ex:
› Cutting down a forest› Blow-outs on the Dunes
Causes of Succession1. Autogenic Factors2. Allogenic Factors
Autogenic Factors Changes introduced by the organisms
themselves Ex: toxins
acids
Allogenic Factors Outside
disturbances Ex: Fire
Floods
Point If you understand the causes and
controlling factors of succession, you can manipulate them
Biogeography Study of the past and present
distributions of individual species and communities
Latitudinal Gradients
Range Limitations1. Lack of dispersion2. Failure to survive in new areas3. Retraction from former range area
Proof Fossil Evidence Pollen Studies Transplant Experiments
Islands Special cases in Biogeography Must be colonized from other areas
Island Species Factors Island size Distance from mainland
Island Size Small islands hold few species Why? Fewer niches available for species to
occupy
Distance from Mainland Closer islands have more species Why? Easier for colonization
Comment Islands tend to have high numbers of
Endemic species Why? Adaptive Radiation and Evolution of
new species
Summary 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.