Transcript Community Ecology CHAPTER 8 Structure Species Interaction Succession & Sustainability Key Concepts Community structure Roles of species Species interactions Changes in ecosystems Stability of ecosystems.

Community Ecology
CHAPTER 8
Structure
Species Interaction
Succession & Sustainability
Key Concepts
Community structure
Roles of species
Species interactions
Changes in ecosystems
Stability of ecosystems
CASE STUDY: FLYING FOXES
• fruit-eating bats
• pollinate flowers from Durian trees
 prized fruit in SE Asia
 strong odor, custard-like “delicious” fruit
• mutualism (durian & flying fox)
• referred to as keystone species
 pollinate plant species
 disperse plant seeds in dropping (biodiversity)
COMMUNITY STRUCTURE

OBJ 8.1
CHARACTERISTICS
1.
Physical Appearance
- stratification, relative size, distribution
2.
Species Diversity
-
1.
richness vs. eveness
Niche Structure
-
ecological Roles of Species
Community Structure: Appearance and
Species Diversity
Fig. 8-2
p. 144
Stratification
SPECIES DIVERSITY
Species richness: # different species
Species evenness: abundance within each of its species
Sample A could be described as being the more diverse as it contains three species
to sample B's two. But there is less chance in sample B than in sample A that two
randomly chosen individuals will be of the same species.
Three Factors Affecting Biodiversity
Latitude(terrestial)- the closer to the equator, the higher the
biodiversity



Highest species diversity in tropics; lowest in polar regions
Depth(aquatic)- biodiversity increases with depth to @ 2000 m
then begins its decrease
Pollution- as levels increase, biodiversity decreases
Ants
Birds
25
20
20
15
15
10
10
5
5
Coast
0
0
Fig. 8-3 p. 145
25
Snails
Species diversity

2,000
Deep Sea
4,000
Depth (meters)
0
6,000 0
Tube worms
Coast
2,000
Deep Sea
4,000
Depth (meters)
6,000
Number of diatom species
Unpolluted
stream
Polluted
stream
Number of individuals per diatom species
Figure 8-4 Page 145
Island Biodiversity

© 2004 Brooks/Cole – Thomson Learning
Rate of immigration
or extinction
High
Theory of Island
Biogeography-the
number of species found
on an island is
determined by:
1.
Species immigration


Low
Equilibrium number
Number of species on island
Immigration
(a)
and extinction rates
2.
Immigration- movement
of organisms into a
place
Emigration- movement
of organisms out of a
place
Species extinction
High
100
© 2004 Brooks/Cole
Thomson Learning
© 2004 Brooks/Cole
– Thomson –
Learning
High
Rate of immigration
or extinction
Rate of immigration
or extinction
Number of amphibian and reptile species
Number of species (percentage of sample studied)
Island Species
50
100
25
10
12.5
Low
Low
Far island
Small island
Near island
Large island
Number of species on island
Number of species on island
6.25
1
0
(c)10 Effect of distance
from1,000
mainland 10,000
100
100,000
Effect
of
island
size
(b)
2,000
4,000
6,000
8,000
10,000
Area (square miles)
Distance from New Guinea (kilometers)
General Types of Organisms




OBJ 8.2
Native-organisms that are naturally found in an ecosystem;
Nonnative (Exotic/ Invasive/Alien)- any organism that is not
found naturally in an ecosystem; usually transported in by
humans
Indicator- organisms that serve as early warnings of damage
to a community
Keystone- organisms whose role in more important than their
numbers or biomass;
Strong interactions with other species affect the life of others
2. Process out materials out of proportion to their numbers or
biomass
1.
Competition
OBJ 8.3
 Competition—Two
organisms
compete to obtain the same limited
resource, and both are harmed to some
extinct.
 Intraspecific—Members
of same
species competing for resources.
 Interspecific—Members of different
species competing for resources.
 The
more similar the competing
species, the more intense the
competition.
OBJ 8.4
Competition

Competitive Exclusion Principle—No two species
can occupy the same ecological niche in the same
place at the same time.

Less fit species must evolve into a slightly different
niche.
Resource Partitioning
OBJ 8.5
Overlapping Niche of
2 species creates
competition
Over time, species
evolve and become
specialized
Fig. 8-7 p. 150
Kinds of Organism Interactions
 Predation—One animal kills/eats
 Predator benefits from food.
another.
 Prey
adaptation is manifested in a higher
reproduction rate.
 Prey
species benefits by eliminating
non-adaptive genes from the gene pool.
 Poorly
adapted predators are less likely to
obtain food and thus pass on non-adaptive
genes.
PREY: DEFENSE MECHANISMS


adaptation the prey uses adds to the chances of
survival for the species
Examples of some defense mechanisms prey use
are:
 Chemical combat
 Camouflage
 Speed
 Trickery: false features and mimicry
OBJ 8.7
Symbiotic Relationships

Symbiosis—Close, physical relationship between
two different species. At least one species derives
benefit from the interaction.

Parasitism—One organism (parasite) living in or on
another organism (host), from which it derives
nourishment.

Ectoparasites—Live on host’s surface.


Fleas
Endoparasites—Live inside host.

Tapeworms
Symbiotic Relationships

Commensalism—One organism benefits, while
the other is unaffected.


Remoras and Sharks
Mutualism—Both species benefit. Obligatory in
many cases as neither can exist without the other.

Mycorrhizae
WHAT IS HAPPENING?
Succession

Succession—A series of regular,
predictable changes in the structure of a
community over time.
 Activities
of organisms change their
surroundings and make the environment
suitable for other kinds of organisms.

Climax community—Stable, long-lasting
community, primarily determined by
climate.
OBJ 8.8
Succession
Primary Succession—Begins with bare
mineral surfaces or water and total lack of
organisms.
 Secondary Succession—Begins with
disturbance of an existing ecosystem.

 Much
more commonly observed.
Primary Succession

Terrestrial Primary Succession



Pioneer Community: Collection of organisms able to
colonize bare rock
(i.e. lichens, mosses).
Lichens help break down rock, and accumulate
debris helping to form a thin soil layer.
Soil layer begins to support small life forms.
Terrestrial Primary Succession







Lichen community replaced by annual plants.
Annuals replaced by perennial community.
Perennial community replaced by shrubs.
Shrubs replaced by shade intolerant trees.
Shade intolerant trees replaced by shade tolerant
trees.
Stable, climax community often reached.
Successional (seral) Stage—Each step in the process.
OBJ 8.9
Terrestrial Primary Succession
Climax Community
Characteristics
Maintain species diversity for extended period.
 Multiple specialized ecological niches.
 High level of organism interactions.
 Nutrients recycled and biomass levels remain
constant.

Aquatic Primary Succession


Except for oceans, most aquatic systems are
considered temporary.
All aquatic systems receive inputs of soil particles
and organic matter from surrounding land.

Gradual filling of shallow bodies of water.

Roots and stems below water accumulate more material.

Wet soil established.
Aquatic Primary Succession
Secondary Succession


Occurs when an existing community is disturbed
or destroyed.
With most disturbances, most of the soil remains,
and many nutrients necessary for plant growth
may be available for reestablishment of the
previous ecosystem.


Nearby undamaged communities can serve as
sources of seeds and animals.
Tends to be more rapid than primary growth.
Terrestrial Secondary
Succession
Modern Concepts of Succession
and Climax

As settlers changed “original” ecosystems to
agriculture, climax communities were destroyed.


Many farms were abandoned, and land began to
experience succession.
Ecologists began to recognize there was not a
fixed, pre-determined community.

Only thing differentiating climax community from
successional community is time scale.