Interactions within communities
• Within an ecosystem, populations of
different species interact in what is called a
• Some organisms within the community
cannot survive independently but rely on
• A niche includes characteristics of an organism,
interaction with _________ and _____________
resources in its environment.
• If habitat s an organism’s “address” then it’s
______ is it’s “occupation”
• Ex. African lions niche food, habitat,
reproduction, climate and behaviour
• Niche: carnivore + environment.
• Fundamental niche (theoretical): the biological
characteristics of the ________and the
________________ that individuals in the
population are theoretically capable of using under
• In reality the lion faces interspecific competition
Thus, ___________________ (a portion of its
• Interactions WITHIN a species
• BETWEEN individuals of different species
(________________) in a ______________
have important influences on population
dynamics of individual species.
CLASSIFICATION of INTERACTIONS between two
Interaction Effect on Population
Competition Interaction may be detrimental to one or both species.
Predation Interaction is beneficial to one species and usually lethal
to the other
Parasitism Interaction is beneficial to one species, and harmful but
Symbiosis not usually fatal to the other
Mutualism Interaction is beneficial to both species
Commensalism Interaction is beneficial to one species and the other is
• Between ________________________
• Restricts ________________________
• 1) Interference competition: interspecific
competition that involves aggression between
individuals of different species who fight over the
• 2) Exploitative competition: interspecific
competition that involves consumption of shared
resources by individuals of different species, where
consumption by one species may limit resource
availability to other species.
• The strongest competition occurs when niches
• Results from interspecific competition:
• weaker competitor could decline in numbers
• one species could change behaviour so it’s able to survive
using different resources
• Individuals in one population could migrate.
• One way individuals of species occupying the
same niche can avoid or reduce competition for
similar resources is by resource partitioning
• Resource partitioning: avoidance of, or reduction
in, competition for similar resources by
individuals of different species occupying
different non overlapping ecological niches.
• It is an example of interspecific interaction in
which the population density of both species
fluctuate. Predator population increases while the
population density of the other species – the prey-
declines. Predator lags behind.
• Can have significant effect on both the predator
and prey population sizes.
• Display a cyclic pattern between the two
• Predator- diverse defense mechanisms that plant
and animal species have evolved through repeated
encounters with predators over time.
• Plants:____________________ defenses: thorns,
hooks, spikes, needles.
• _________________ defenses: eg. Mustard family
of plants contains oils that make them toxic.
Example of interesting defenses:
• ___________________ can sometimes affect competition.
• Ex. Passionflowers vines produce toxic chemicals to
protect it. Heliconius butterfly is able to feed on the vines
because it has enzymes that break down the chemicals.
• They also lay their eggs on the leaves of the flower- the
eggs are bright yellow so other butterflies avoid them it
and reduces intraspecific competition.
• The plants have coevolved yellow nectaries that resemble
the eggs to discourage Heloconius from laying eggs on the
• ________________ defense mechanisms include
• ___________ defense mechanism might be
• Active defense mechanisms are more costly in
energy then passive.
• __________ defenses include alarm calling
• Camouflage is also used by prey to help blend into
the background (passive defence mechanism)
• Defense colouration can help show predators that
they are poisonous or distasteful
• Mimicking – gaining an advantage
by resembling a distasteful species
• Named after the scientists that discovered
• A ________________ or harmless species mimics
an unpalatable or harmful one (most often
observed in moths and butterflies) Monarch
• Different species resemble one another
• All are poisonous or dangerous so predators are
warned by the colouration.
• Evolved similar colouring to minimize predation.
• This term means “living together”. Individuals of
two different species live in close, usually
physical, contact. At least one of the individuals
benefits from the association.
Three types of symbiotic relationship:
• Mutualism: A symbiotic relationship in which
_______________________; as neither is harmed,
it is categorized as a +/+ relationship.
• Obligatory Mutualism: neither species could
survive without the other.
• Commensalism: a symbiotic relationship in
which one organism benefits and the other
organism is unaffected; This is a __________
• Parasitism: one organism (the parasite) benefits
at the expense of the host. The host is often
harmed but usually not killed; [ +/-]
• Microparasites: microscopic in size . ex.
______________ protozoan that causes malaria.
• Endoparasites: live and feed _________ the
host’s body. Ex. A tapeworm (also a
• Ectoparasite: Live and feed on the ________
surface of the host, such as lice.
• Pg 691 (Investigating Predator- Prey
• Symbiosis worksheet