Month Day Topic
Nov.
8
Individuals to populations
10 Holiday!
13 Populations to communities
15 Community patterns
17 Ecosystems
20 Film-1st showing
22 Film-2nd showing
24 Holiday!
27 Ecosystem services
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
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
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
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
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
Batesian mimicry
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/-)
Commensalism
(0/+)
Mutualisms
(+/+)
Mutualisms can be loose or tight
Acacia with ants
Acacia without ants
Communities are...
• Defined by abiotic factors
– Populations in a community have similar
fundamental niches
• Defined by biotic interactions
– Weak and strong interactions determine a
population’s realized niche
• Dynamic
– Vary in time and in space
Why do communities vary in
time?
Communities are...
Comprised of populations that respond
individualistically to change
Communities vary in time
Ecological succession:
a sequence of change in the species
composition of a community
Succession
1. Primary
– establishment of communities on new
sites that previously had no organisms
1949
2001
Succession
1. Primary
– establishment of communities on new
sites that previously had no organisms
2. Secondary
– re-establishment of communities
following disturbance
Why do communities vary in
space?
Communities vary in space
•
•
•
•
•
Time
Relief/aspect
Parent material
Climate
Organisms
Terrestrial biome
Terrestrial biome
• A major community type that differs
from other types in the structure of its
dominant vegetation.
Terrestrial biome
• A major community type that differs
from other types in the structure of its
dominant vegetation.
• Primarily controlled by climate.
– Relationship between rainfall and
temperature
Biomes
• The vegetation of a biome has a similar
appearance wherever on Earth that
biome is found.
• In many cases, this is due to convergent
evolution.
Euphorbiaceae
Cactaceae
Tundra
Tundra
-severe winters
-short growing season,
cool summer
-arctic or alpine
Tundra
Temperate Forest
Temperate forest
Temperate Forest
-distinct winter
season,
frost a defining
feature
-summer season
usually moist
Temperate Forest
Desert
Desert
-hot or cold deserts
exist
-low precipitation
Desert
Tropical Rain Forest
-found near the
equator
-temperature varies
little from
approximately 23°C
-Over 2 m of rainfall
Tropical Rain Forest
Tropical Rain Forest
-canopy trees up to 55 m tall -soils are generally unfertil
-largest biome, on an area basis
-nutrients and carbon store
in plant biomass, not soils