Download Ecology

Def. “all the populations of organisms
inhabiting a common environment and
interacting with one another”
 Interspecific
interactions—occur between
populations of different species
 Coevolution—a
change in one species acts
as a selective force on another species
 Symbiosis—
For at least part of the life
cycle, individuals of two or more species
interact with neutral, positive. Or negative
effects on each other

A niche is a way of life, or a role in an ecosystem. an organism’s role
in the environment (its profession, not its address)
Includes the
habitat, food
sources, other
resources that are
necessary to the
survival of the
organism.
Two Types
•Fundamental
•Realized
Fundamental niche - determined by the
physiological limits of the organism
Realized niche - the portion of the
fundamental niche actually utilized due
to interactions with other species

e.g. Chthamalus and Balanus barnacles
1) Interspecific Competition (–/–)
 Competition occurs when 2 or more
populations overlap in their niches
• Limiting resources
 Food
 Space

Two possible
Outcomes
1. Weaker competitor
becomes extinct
2. One or both
species may evolve
enough to use a
different set of
resources

Competition cannot
operate for long
periods of time
Resource partitioning- The subdividing of some
category of similar resources that lets competing
species coexist.
2) Predation (+/–)
consumption of one
organism by another
• Predator eats prey
3) Parasitism (+/–)—specialized predator (parasite) lives
on/in its host, not killed immediately
Endoparasitism—live inside host (tapeworms/viruses)
Ectoparasitism—live on surface
of host (mosquitoes/aphids)
4) Commensalism (+/0)—one partner
benefits while not harming the other
5) Mutualism (+/+) both partners benefit.
Lichens-association between fungus and
algae
Nitrogen-fixing bacteria and legumes
Populations of other species are part of any
organism’s environment, and the ones that interact
as predators and prey exert selection pressure on
each other. One must defend itself and the other
must overcome the defenses. This is the basis of an
evolutionary arms race that has resulted in amazing
adaptations.
Some prey species gain protection from
camouflage, they hide in the open. Such
species have adaptations in their form,
patterning, color, and behavior that help them
blend with the surroundings and escape
detection.
Many prey species taste bad, are toxic, or inflict pain on attackers.
Toxic types often have warning coloration, or conspicuous patterns
and colors that predators learn to recognize and avoid.
Aposematic coloration
Red/black; yellow/black
Mimicry—prey resembles
species that cannot be
eaten.
Batesian mimicry:
Imitate color patterns or
appearance of more
dangerous organisms
Müllerian mimicry describes a situation where
two or more species have very similar warning
or aposematic signals and both share genuine
anti-predation attributes.
Prey that are cornered or
under attack may turn on a
last chance trick to avoid
predation.