Transcript Community Ecology

Chapter 47
Community
Ecology
Community Ecology
Outline
The Concept of the Community
Diversity and Composition Models
The Structure of Communities
Island Biogeography
Habitat and Ecological Niche
Competition Between Populations
Predator-Prey Interactions
Symbiotic Relationships
Community Development
Community Biodiversity
2
Community Ecology
Community Concept
An assemblage of populations interacting with
one another within the same environment
Composition is a listing of various species in the
community
Diversity includes both species richness and
species diversity
3
Community Structure
4
Community Ecology
Diversity and Composition Models
Gleason - Individualistic Model
Each population is there because its abiotic
requirements are met
Clements - Interactive Model
Community is the highest level of organization
Dependent on biotic interactions
5
Species Richness of Communities
6
Community Ecology
Island Biogeography
MacArthur and Wilson
Developed a general model of island
biogeography
Explains and predicts how the community
diversity of an island is affected by
- Distance from the mainland, and
- Size of the island
7
Model of Island Biogeography
8
Community Ecology
Community Structure
Competition
When two species compete, the abundance of
both species is negatively impacted
Predation (or parasitism)
- Expected to increase the abundance of the
predator (or parasite)
- And reduce the abundance of the prey (or host)
9
Community Ecology
10
Habitat and Ecological Niche
Habitat
The area an organism lives and reproduces in
Ecological niche
The role a species plays in its community
- Includes its habitat, and
- Its interactions with other organisms
Fundamental niche - All conditions under which
the organism can survive
Realized niche - Set of conditions under which it
exists in nature
Feeding niches for Wading Birds
11
Community Ecology
12
Competition Between Populations
Interspecific competition
Members of different species require the same
resource
The supply of the resource is limited
Competitive Exclusion Principle
No two species can occupy the same niche at the
same time
Resource Partitioning decreases competition
Can lead to character displacement
Competition Between
13
Two Laboratory Populations of Paramecium
Character Displacement in Finches
on the Galápagos Islands
14
Niche Specialization Among
Five Species of Coexisting Warblers
15
Competition Between
Two Species of Barnacles
16
Community Ecology
Predator-Prey Interactions
Predation
One living organism, the predator, feeds on
another, the prey
- Predator is larger
- Predator has lower reproductive rate
- Prey usually entirely consumed
Presence of predators can decrease prey
densities, and vice-versa
17
Predator-prey Interaction Between
18
Paramecium caudatum and Didinium nasutum
Predator-prey Interaction
Between a Lynx and a Snowshoe Hare
19
Community Ecology
Prey Defenses
Prey defenses
Mechanisms that thwart the possibility of being
eaten by a predator
- Spines
- Tough Epidermis
- Poisonous Chemicals
- Camouflage
- Bright Coloration
- Flocking Behavior
20
Camouflage in the Anglerfish
21
Anti-predator Defenses
22
Community Ecology
23
Mimicry
Mimicry
One species resembles another species
Mimicked species possesses an overt
antipredator defense
Batesian Mimicry - Mimic lacks defense of the
organism it resembles
Müllerian Mimicry - Mimic shares same protective
defense
Mimicry Among Insects with
Yellow and Black Stripes
24
Community Ecology
25
Symbiotic Relationships
Symbiosis
Interactions in which there is a close relationship
between members of two species
Parasitism
- Parasite derives nourishment from a host, and may
use host as habitat and mode of transmission
 Endoparasites
 Ectoparasites
The Life Cycle of a Deer Tick
26
Community Ecology
27
Commensalism
Symbiosis, cont.
Commensalism
- A symbiotic relationship in which one species
benefits and the other is indifferent
 Remoras
and Sharks
- Many supposed examples may turn out to be
mutualism or parasitism
- Inferred amount of harm or benefit two species do
to one another is subject to investigator bias
Clownfish Among
Sea Anemone’s Tentacles
28
Community Ecology
29
Mutualism
Symbiosis, cont.
Mutualism
- A symbiotic relationship in which both members of
the association benefit
- Need not be equally beneficial to both species
 Cleaning
Symbiosis
- Often help each other obtain food or avoid
predation
 Bacteria
in human intestinal tract
Mutualism Between
the Bullhorn Acacia Tree and Ants
30
Cleaning Symbiosis
31
Community Ecology
32
Community Development
Ecological Succession
A predictable pattern of change in species
replacements following a disturbance
- Primary Succession occurs in areas where there is
no soil formation
- Secondary Succession begins in areas where soil
is present
 Pioneer
Species
Secondary Succession
33
Secondary Succession
in a Forest
34
Community Ecology
35
Succession Models
Facilitation Model
Each stage facilitates invasion and replacement
by organisms of the next stage
Succession in a particular area will always lead to
the same type of community
Climax Community
Community Ecology
36
Succession Models
Inhibition Model
Colonists remain and inhibit growth of other
plants until the colonists are damaged or die
Tolerance Model
Different types of plants can colonize an area at
the same time
Chance determine which seeds arrive first
Community Ecology
Community Diversity
Community stability can be recognized in three
ways
Persistence through time
Resistance to change
Recovery once a disturbance has occurred
37
Community Ecology
Intermediate Disturbance Hypothesis
If widespread disturbances occur frequently,
diversity will be limited
If diversity is high, only moderate disturbances
have been occurring with moderate frequency
38
The Intermediate Disturbance Hypothesis 39
Community Ecology
Predation, Competition, and Biodiversity
Predation by a particular species may reduce
competition and increases diversity
Such predators are referred to as keystone
predators
Exotic species
May lead to unbridled competition
Resultant reduction in biodiversity
40
Effect of a Keystone Species
41
Community Ecology
Review
The Concept of the Community
Diversity and Composition Models
The Structure of Communities
Island Biogeography
Habitat and Ecological Niche
Competition Between Populations
Predator-Prey Interactions
Symbiotic Relationships
Community Development
Community Biodiversity
42
Ending Slide Chapter 47
Community
Ecology