Outline

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Outline

• What determines where a species lives?
• Communities
• Ecological interactions

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A population is
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A population is

• A group of individuals of the same species living
  in a given area at a given time.

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What controls where a population lives?
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What controls where a population lives?

• It has to get there
• Evolution
• Dispersal

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What controls where a population lives?

• It has to get there
• Evolution
• Dispersal
• Its ecological niche

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Key concept in ecology the niche
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Key concept in ecology the niche

• Fundamental niche
• Abiotic conditions that the species can live
  within

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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

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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
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Interactions among populations determine a
species realized niche...
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A community is
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A community is

• Populations of different species that live
• together in a given area at a given time.

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Communities are...

• Defined by abiotic factors
• Populations in a community have similar
  fundamental niches

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Communities are...

• Defined by abiotic factors
• Populations in a community have similar
  fundamental niches
• Defined by biotic interactions
• Some are weak
• Some are strong

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Types of community interactions
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Types of community interactions
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Types of community interactions
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Types of community interactions
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Keys to competition(-/-)

• Organisms compete for limited resources

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Keys to competition

• Organisms compete for limited resources
• Can be
• Intraspecific

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Population size
Time
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Keys to competition

• Organisms compete for limited resources
• Can be
• Intraspecific
• Interspecific

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Figure 55.2
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Competition can

• Restrict species ranges

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Competition can

• Restrict species ranges
• Reduce species abundances

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Competition can

• Restrict species ranges
• Reduce species abundances
• Cause the local extinction or competitive
  exclusion of species from an area

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Figure 55.3
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The ghost of competition past...
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Predator-prey interactions(/-)

• Predators are generally larger than their prey
  (but many exceptions...)

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Predator-prey interactions

• Predators are generally larger than their prey
  (but many exceptions...)
• Predators live outside of the body of their prey

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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

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Predator-prey interactions

• Dynamics of predator and prey populations may be

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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

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Tightly coupled predator-prey interactions change
over time

• An evolutionary arms race

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Tightly coupled predator-prey interactions change
over time

• An evolutionary arms race
• Mimicry

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Batesian mimicry

• Figure 55.10

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Batesian mimicry

• Figure 55.10

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Predator-prey interactions change over time

• An evolutionary arms race
• Mimicry
• Plant defenses against herbivores

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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

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Amensalism(0/-)

• Figure 55.11

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Commensalism(0/)

• Figure 55.12

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Mutualisms(/)

• Mutualisms can be loose or tight

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Picture of cleaner wrasse picking parasites off
of other species of fishes
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Figure 55.13
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Picture of cross section of acacia thorn stuffed
full of ant larvae
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Acacia with ants
Acacia without ants
Figure 55.14