Transcript Interactions within Communities

Interactions within
Communities
Grade 9/10 Review
• Individuals of the same species living in the same area
make up a population.
• Populations of different species living in the same area
form a community.
Niche Definitions
• Ecological niche: the role an organism fills
within a community (includes what it does, eats,
basically anything that describes its pattern of
living)
• Fundamental niche: has the biological
characteristics of the organism plus the set of
resources it is capable of using under ideal
conditions (no interspecific competition exists).
• Realized niche: the portion of the fundamental
niche the organism actually fills.
Competition
• Intraspecific
competition:
competition for
resources between
members of the same
species.
Competition
• Interspecific
competition:
competition for
resources among
members of two or
more different
species.
Interspecific Competition
• Competition between two species can be
interference competition in which the two
species are actually fighting over the resources
(i.e. birds fighting over birdhouses).
• Exploitative competition is where the two
species are using a common resource (i.e. arctic
foxes and snowy owls eating arctic hares).
Interspecific Competition
• Gause’s Principle/Principle of Competitive
Exclusion: if the resources are limited, no two species
can remain in competition for exactly the same niche
indefinitely. One species will always out compete the
other species and drive the other to extinction.
Gause’s Principle
Resource partitioning
• Resource partitioning: the avoidance of, or
reduction in, competition for similar resources by
individuals of different species that do no occupy
the same niche
(i.e. plants in the same area will have different
root structures so each species is able to get
nutrients and water from the soil and not
compete with the other species).
Symbiosis
• Symbiosis:
interactions in which
members of two (or
more) species
maintain a close
association.
• The following slides
are types of
symbiosis.
Parasitism
• Parasitism: the interaction is beneficial to one
species and harmful (not fatal) to the other
species.
• Parasites can be both micro- and macro- as
well as ecto- and endo-.
• Social parasites mimic the behaviour of
another species in order to complete their
lifecycle (i.e. cowbirds)
Ecto-parasites and Endo-parasites
Mutualism
• Mutualism: the
interaction is beneficial
to both species.
• Obligatory mutualism is
when neither species
can survive without the
other such as with
lichens (fungi and
algae/cyanobacteria).
Commensalism
• Commensalism: the
interaction is
beneficial to one
species while the
other is unaffected.
• Remoras and sharks
are a possible
example.
Commensalism or Mutualism?
Predator-Prey Relationships
• Predator-prey relationships are an
important interspecific interaction in a
community.
• When the prey population increases, the
predator population will increase shortly
thereafter. Predator-prey populations
follow cyclical pattern.
Stuff you know already!
• Predator-prey interactions have caused prey to evolve
diverse defense mechanisms in order not to be eaten.
• Predators are evolving to bypass these defenses
(Evolutionary Arms Race!)
Plants
• Plants use both morphological defenses such as
thorns, hooks, needles, spines and chemical defenses
such as toxins, hormones and other chemicals to deter
herbivores from eating them.
Animals
• Animals use passive
defenses such as
hiding or active
defenses such as
fleeing.
•
Mimicry
Some animals use mimicry, which is one
species appearing very similar to another
species.
• There are two types of mimicry:
1) Batesian mimicry: a harmless species mimics
a harmful one (i.e. edible butterfly species
mimics a toxic species so it won’t get eaten).
2) Mullerian mimicry: where two or more
dangerous species appear similar which
causes their common predators to learn
quicker to avoid them (i.e. poisonous butterflies
all look similar)
Mimicry