Month Day Lecture
Oct.
24 Individuals I
29 Individuals II
31 Populations
Nov.
5
7
12
14
Communities
Conservation
Biology
Biogeography
Ecosystems
19
Exam 3
Activity
Chimps
Population
growth
Biological
Invasions
Exam
review
Chap.
53
53
54
55
58
57
56
53-58
Outline
• What determines where a species
lives?
• Communities
• Ecological interactions
A population is:
A population is:
A group of individuals of the same species
living in a given area at a given time.
What controls where a
population lives?
What controls where a
population lives?
• It has to get there
– Evolution
– Dispersal
What controls where a
population lives?
• It has to get there
– Evolution
– Dispersal
• Its ecological niche
Key concept in ecology:
the niche
Key concept in ecology:
the niche
• Fundamental niche
– Abiotic conditions that the species can live
within
Key concept in ecology:
the niche
• Fundamental niche
– Abiotic conditions that the species can live
within
• Realized niche
– Biotic interactions that reduce or enhance
the fundamental niche
Barnacle story, figure 55.1
Balanus’ fundamental niche: upper, middle and lower zone
Balanus’ realized niche: middle zone, limited from upper by
competition, lower by predation
Interactions among
populations determine a
species realized niche...
A community is:
A community is:
Populations of different species that live
together in a given area at a given time.
Communities are...
• Defined by abiotic factors
– Populations in a community have similar
fundamental niches
Communities are...
• Defined by abiotic factors
– Populations in a community have similar
fundamental niches
• Defined by biotic interactions
– Some are weak
– Some are strong
Types of community interactions
Individual 2
Harm
Ind. 1
No effect
Benefit
Harm
Competition Amensalism
Predation or
Parasitism
No effect
Amensalism
Commensalism
Benefit
Predation or Commensalism Mutualism
Parasitism
Types of community interactions
POP. 2
POP. 1
Harm
No effect
Benefit
Harm
Competition
Amensalism
Predation or
Parasitism
No effect
Amensalism
Benefit
Predation or
Parasitism
Commensalism
Commensalism Mutualism
Types of community interactions
POP. 2
Harm
POP. 1
No effect
Benefit
Harm
Competition Amensalism
Predation or
Parasitism
No effect
Amensalism
Commensalism
Benefit
Predation or Commensalism Mutualism
Parasitism
Types of community interactions
POP. 2
Harm
POP. 1
No effect
Benefit
Harm
Competition Amensalism
Predation or
Parasitism
No effect
Amensalism
Commensalism
Benefit
Predation or Commensalism Mutualism
Parasitism
Keys to competition
(-/-)
• Organisms compete for limited
resources
Keys to competition
• Organisms compete for limited
resources
• Can be:
– Intraspecific
Time
Population size
Keys to competition
• Organisms compete for limited
resources
• Can be:
– Intraspecific
– Interspecific
Figure 55.2
Competition can:
• Restrict species ranges
Competition can:
• Restrict species ranges
• Reduce species abundances
Competition can:
• Restrict species ranges
• Reduce species abundances
• Cause the local extinction or
competitive exclusion of species from
an area
Figure 55.3
The ghost of competition
past...
Predator-prey interactions
(+/-)
• Predators are generally larger than their
prey (but many exceptions...)
Predator-prey interactions
• Predators are generally larger than their
prey (but many exceptions...)
• Predators live outside of the body of
their prey
Predator-prey interactions
• Predators are generally larger than their
prey (but many exceptions...)
• Predators live outside of the body of
their prey
• Predators generally kill their prey
Predator-prey interactions
• Dynamics of predator and prey
populations may be:
Predator-prey interactions
• Dynamics of predator and prey
populations may be:
• Loosely coupled
– predator “switches” when prey is scarce
• Tightly coupled
– predator starves when prey is scarce
Tightly coupled predator-prey
interactions change over time
• An evolutionary “arms race”
Tightly coupled predator-prey
interactions change over time
• An evolutionary “arms race”
• Mimicry
Batesian mimicry
• Figure 55.10
Batesian mimicry
• Figure 55.10
Predator-prey interactions
change over time
• An evolutionary “arms race”
• Mimicry
• Plant defenses against herbivores
Host-parasite interactions
(+/-)
• Parasites are generally smaller than
their hosts
• Parasites live inside or on the body of
their host
• Parasites generally kill their hosts more
slowly than predators
Amensalism
(0/-)
• Figure 55.11
Commensalism
(0/+)
• Figure 55.12
Mutualisms
(+/+)
Mutualisms can be loose or tight
Picture of cleaner wrasse
picking parasites off of other
species of fishes
Figure 55.13
Picture of cross
section of acacia
thorn stuffed full of
ant larvae
Acacia with ants
Figure 55.14
Acacia without ants