Wildlife 10/20
Symbiosis
is the close and often long
lasting relationship that exists
between two biologically different
species.
 The
definition of symbiosis is controversial
among scientists. Some believe symbiosis
should only refer to persistent mutualisms,
while others believe it should apply to any
types of persistent biological interactions.
 Examples
of this would include Parasitic,
Commensalistic and Mutualistic interactions.
 Some
symbiotic relationships are obligate,
meaning that both organisms entirely depend
on each other for survival. For example, some
lichens cannot live without other lichens being
present.
 Others
are facultative, meaning that they can
rely on other organisms, but they do not have to
interact with the other organism in order to
survive.
 Mutualism
is any relationship between
individuals of different species where both
individuals derive a benefit.
 In
general, only lifelong interactions involving
close physical and biochemical contact can
properly be considered symbiotic.
 Mutualistic
relationships may be either
obligate for both species, obligate for one but
facultative for the other, or facultative for both.


An example is the Clownfish which feeds on
small invertebrates that potentially cause harm
to Sea Anemones. The territorial Clownfish also
chase away other fish that feed on anemones.
The fecal matter from the Clownfish provides
nutrients for the sea anemone to feed on.
The Clownfish also receives a benefit in that it
is protected from predators by the Anemone's
stinging cells. The Clownfish has developed a
protective mucus that is found around its body
that protects it from the tentacles of the
Anemones.


Commensalism describes a relationship
between two living organisms where one
benefits and the other is not significantly
harmed or helped.
For example, Cattle Egrets forage in fields
among cattle or other livestock for food. As
cattle and other livestock graze, they cause
movements that stir up various insects that the
Cattle Egrets then feed on. The Egrets benefit
from this but the livestock are typically
unaffected by this relationship.
 There
are three specific types of Commensalist
relationships :
 Metabiosis- When
an organism uses something
another organism has created as a home.

Phoresy- Involves one organism using another
for transportation
 Inquilinism-
When one organism uses another
organism as a home.
 Metabiosis-
Hermit Crabs using snail
shells to protect their bodies.
 Phoresy-
This category mainly includes
insects that travel on other organisms.
 Inquilinism-
Orchids that grow on trees,
or birds using holes in cactus and trees
as nests.



A parasitic relationship is one in which one member of
the association benefits while the other is harmed.
An example is the cowbird, which do not build nests of
their own but rather deposit their eggs in nests of other
species. The host bird raises the young as their own.
The cowbird’s parasitism does not necessarily harm its
host’s brood.
However, some may remove one or more host eggs to
avoid detection, and furthermore the young cowbird
may heave the host’s eggs and nestlings out of the nest.
 Parasitic
Relationships:
 Endoparasites-
Organisms that live within the
host's body in order to survive. For example,
Tape Worms.
 Ectoparasites-
Organisms that live on the
surface of the host organism’s body. For
example, Mites.
 Parasites

may be...
Necrotrophic- The parasite
kills their host as they use
them. For example, Strangler
Fig.
 Biotrophic- The
parasite relies
on their host's surviving. For
example, Leeches.