Learning outcomes
• Describe the 5 interspecific relationships and
the effect they have on each partner of the
relationship
• Explain what happens to the population and
individual when intraspecific competition
takes place
Interrelationships
Intraspecific relationships
• Relationships between organisms of the same
species
• Very strong interactions
– Co-operative
• E.g. Courtship, looking after young,
hunting in packs
– Aggressive
• E.g. Fighting for mates and territories
Interspecific relationships
• Relationships between organisms of different
species
• 5 main relationships
Mutualism
Both partners benefit from the relationship
Commensalism
• One partner benefits while the other partner
is in-different
Amensalism
• The presence of one species has a harmful
effect on the other, but is not affected by the
association itself
Antibiosis
• One partner is harmed while the other
partner is in-different
Exploitation
• One member of the partnership benefits while
the other is harmed
Overview
Mutualism
Commensalism
A
B
Benefits
Benefits
A
B
Not affected
Antibiosis
Amensalism
A
B
Benefits
Harmed
A
B
Not affected
Exploitation
Benefits
Harmed
A
B
Harmed
Benefits
Activity
• Complete pg 309 in Biozone
Intraspecific Competition
• Members of the same population have the same
resource requirements from the environment
• What are these resources?
• What happens when these resources are limited?
When resources are limited
• Populations - reduce their population growth
rate (lower birth rates and/or higher
mortality)
• Individuals – reduce their growth rate and
mature at a smaller size, some may not breed
Intersepcific Competition
• Competitive exclusion principle (Gause’s
principle)
“No two species with similar needs for the same
limiting resources can coexist in the same
place.”
• Window and Notch caterpillars