Download Population Interactions

Population Interactions
“Chapter 23”
Questions
• Questions 1-3 page 762
Interactions within communities
• Populations do not live in isolation
• Populations of different species interact in
a community.
• Each occupies its own ecological niche
Symbiosis
• Includes a variety of interactions in which
two species live together in close, usually
physical, association. Parasitism,
mutualism and commensalism are
different types of symbiosis.
Interspecific Competition
• Occurs between individuals of different
species and restricts population growth.
• Can occur in 2 ways:
1) fighting (interference competition)
2) use of shared resources
(exploitative competition)
• Competitive exclusion – limited resources,
no two species can remain in competition
for exactly the same niche indefinitely
• Resource partitioning – avoidance of or
reduction in competition for similar
resources
Predation
• Interspecific interaction in which
population of one species increases
(predator) while the prey decrease.
Defense Mechanisms
• Predator prey interaction have resulted in
the evolution of various defence
mechanisms in plant and animal species.
• Some include: thorns, hooks, spines and
needles and chemical defence behaviors.
• Others include: hiding, fleeing, mimicry
Symbiosis
• Meaning living together.
• Two different species live close, usually in
physical contact.
• There are three types: 1) mutualism
2) commensalism
3) parasitism
Mutualism
• Both organisms benefit.
• Example: bacteria live in the guts of
herbivores such as cows, deer and sheep.
• They do not produce enzymes to break
down cellulose. The bacteria secrete an
enzyme to break it down.
Commensalism
• Caribou and fox
• Where they can both benefit or be
harmed.
Parasitism
• Parasites live and feed on their host.
Without them they will not survive.
• There is little or no harm to the host.
Disruption of Community
Equilibrium
• A variety of disturbances can affect
equilibrium.
• Natural disasters, introduction of exotic
species.
Questions
• Question 1-7 page 771
Succession
• Describes the gradual changes in vegetation of
an area as it develops toward a final stable
community called a climax community
• Primary succession occurs in an area in which
no community existed previously, for example a
volcanic eruption or when bare rock or mineral
soil is exposed by human activity or from
beneath a retreating glacier.
• Lichens and mosses, usually the first to colonize
the bare rock surface.
• Secondary succession – occurs when a
community is partially or completely destroyed
and its dominant plant species have been
eliminated. Such destruction may result from
causes such as fire, flooding, landslides or
human disturbances. Re-growth is best known
as secondary succession.
• Pioneer community – the first species to appear
during succession.
Questions
• Questions 1-9 page 775.
• Review Questions page 780 -781
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BIOLOGY 30
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