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Outcomes of Competition
 Niches of similar species may overlap. Two
species cannot compete for the same
limiting resource for long.
 eventually one species outcompetes the
other
 One species survive, other emigrates OR
dies out
 Even a minute reproductive advantage
leads to the replacement of one species by
the other.
 This is called the COMPETITIVE
EXCLUSION PRINCIPAL.
Evidence for
Competitive
Exclusion
the Russian ecologist, G.F.
Gausse demonstrated that
Paramecium aurellia
outcompetes and displaces
Paramecium caudatum in
mixed laboratory cultures,
apparently confirming the
principle.
Resource Partitioning
When two or more similar
species coexist, such as
these varieties of
warbler, each species
only uses part of the
available resources. This
is called resource
partitioning.
(species sharing
resources)
PARASITISM
 Parasitism is a species interaction that
resembles predation in that one individual is
harmed while the other benefits.
 However, in parasitism, the parasite feeds on
the host individual.
 This does not result in the immediate death of
the host. Rather, the parasite may feed on the
host for a long time instead of killing it.
Ectoparasites
 Ectoparasites are
external parasites.
 They live on their
hosts body, but do
not enter it.
 Examples include
ticks, fleas, lice,
lampreys, leeches
and mosquitoes
Endoparasites
 Endoparasites are
internal parasites,
and live inside the
host’s body
 Endoparasites
include bacteria and
other microorganisms, and
many worms
Resource partitioning amongst plants
Different species
of plants in the
same habitat will
compete for the
same resources
like light, water,
mineral salts, etc.
Different species
of plants grow to
different heights
or have roots that
are different
lengths so they
divide the
resources,
accessing them in
slightly different
ways
Resource partitioning: co-existing
shore birds
Human influence on community
structure
The elephant herd in the Kruger National Park
increased from 8, 000 to 12,500 in 2008 and to
19 000 in 2009. The elephant population is
increasing by 7% per year, and might reach 20 000
by 2012. This large herd cannot be sustained since
adult elephants consume 130 kg food a day and
they live for 55 – 65 years.
On 25 February 2008 the SA Government finally
concluded it would have to lift a 17 year-old
moratorium on the culling of the native elephant to
cope with its booming population. Minister van
Schalkwyk announced that killing of excess animals
would only be allowed once all other options
(translocation and contraception) had been ruled
out.
Minister van Schalkwyk said:”Our simple reality is
that elephant population density has risen so
mulch in some southern African countries that
there is concern about impacts on the landscape,
the viability of other species and the livelihoods
and safety of people living within elephant ranges.”
Mutualism
 Mutualism is a symbiotic relationship in which
both members of the association benefit.
 Often help organisms obtain food or avoid
predation.
 Bacteria in human intestinal tact.
 Need not be equally beneficial to both species.
 Cleaning Symbiosis
Pollination
 Pollination is the
most important of
the mutualistic
relationships.
 The plant
provides food for
the pollinators,
which in turn
carries the pollen
to another flower
COMMENSALISM
Is a relationship in which one species benefits
and the other is not affected