Community Interactions
 Symbiosis
Abiotic Factors
Temperature
Topography
Water
Abiotic Factors
Sunlight
Soil Content
Communities and Populations
Communities
Populations
 Assemblage of different
 Group of individuals of the
populations that live together
in a defined area.
same species that live in the
same area.
Niche
 Each species unique living arrangement in a
community
 A full range of physical and biological conditions in
which an organism lives and the way in which the
organism uses those conditions.
 Includes:
 Habitat
 Food sources
 Time of day organism is most active
 Predator
 Reproduction
Symbiosis
 Any relationship where
two species live closely
together
 Symbiosis literally means
“living together”
 3 main types
 Mutualism
 Commensalism
 Parasitism
Mutualism I Win – You Win (+,+)
 Both species benefit from relationship
Symbiotic Mutualism
A remarkable 3-way
mutualism appears to have
evolved between an ant, a
butterfly caterpillar, and an
acacia in the American
southwest. The caterpillars
have nectar organs which
the ants drink from, and
the acacia tolerates the
feeding caterpillars. The
ants appear to provide
some protection for both
plant and caterpillar
Commensalism I Win (+,0)
 One member of the association benefits and the other
is neither helped nor harmed
Commensalism
Parasitism I win – You lose (+,-)
Parasitism
 One organism lives on or inside another organism
and harms it
 Parasite obtains all or part of its nutrients from the
other organism
 Host
 Organism that is harmed in relationship; the one that
provides the nutrients to the parasite
 Parasite
 Organism that gets its nutrients from the host
 Do they want to kill their host?
 No, because they need them…they will weaken or hurt
the host in some way
Symbiotic Parasitism
One Benefits, One is Harmed
Hook Worm
Cutaneous larva migrans
Filariasis worm
Parasitism
Loa Loa Blood Dwelling Nematode in the
conjunctiva of the eye
Parasitism
You’re not seeing things. There are isopods in
that fish’s mouth. And they’re not simply
hiding in there – they’ve completely replaced
the fish’s tongue. Meet the tongue-eating
isopod (Cymothoa exigua).
Isopods are crustaceans, and one group of
them – the Cymothoidae – parasitize fish.
Most species are simple ectoparasites that
feed on the fish’s skin or gills. C. exigua goes
further. The isopod gets into its host’s mouth
and grabs onto its tongue with seven hooklike
legs. Over time, the tongue degenerates,
leaving the parasite hanging on to its stub.
This change actually has very little effect on
the fish, because it can still hold prey with the
parasite. The isopod doesn’t just replace the
tongue physically, it also replaces it
functionally.
 Symbiosis
Community interactions
 Symbiosis-any relationship in which two species live
closely together
 Mutualism
 Commensalism
 Parasitism