Download Ch 8 Community Ecology

Chapter 8
Community Ecology
Importance of Biodiversity
Question of the Day
The best example of a tertiary consumer would
be a/an
a. mouse
b. grasshopper
c. sheep
d. cactus
e. coyote
Section 8-1
Community Structure &
Species Diversity
Question to Consider
How does community structure affect species diversity?
COMMUNITY STRUCTURE
 Biological
communities differ in their structure
and physical appearance.
Figure 8-2
Physical Characteristics
 Physical
appearance: the relative sizes,
stratification, and distribution of its
populations and species
 Transition
occurs around the edges, where
two community types interact.
 Increased
edge area may be harmful due to
habitat fragmentation; many species become
more vulnerable to predators and loss of
colonization ability.
Species Diversity
 Biological
communities differ in the types and
numbers of species they contain and the
ecological roles those species play.
 Species
diversity: the number of different
species it contains (species richness)
combined with the abundance of individuals
within each of those species (species
evenness).
Niche Structure
 Niche
structure: how many potential
ecological niches occur, how they resemble
or differ, and how the species occupying
different niches interact.
 Geographic
location: species diversity is
highest in the tropics and declines as we
move from the equator toward the poles.
Species Diversity on Islands
 MacArthur
and Wilson proposed the species
equilibrium model or theory of island
biogeography in the 1960’s.
 Model
projects that at some point the rates of
immigration and extinction should reach an
equilibrium based on:
Island size
 Distance to nearest mainland
Why?

Conserving Biodiversity
Section 8-2
Types of Species
Question to Consider
How does a species’ role affect biological
communities?
Question of the Day

Q: Which of the following best illustrates the concept of
the tragedy of the commons?





A. Destruction of landscape by surface
mining on private land
B. Selective harvesting of trees by a timber
company in a national forest
C. Legislation of catch limits to avoid
depletion of fish stocks in a shared lake
D. Inadvertent destruction of beneficial
species while attempting to control pests
E. Depletion of an aquifer by regional farmers
TYPES OF SPECIES
 Native,
nonnative, indicator, keystone, and
foundation species play different ecological
roles in communities.


Native: those that normally live and thrive in a
particular community.
Nonnative species: those that migrate,
deliberately or accidentally introduced into a
community.
Kudzu
Indicator Species:
Biological Smoke Alarms
 Species
that serve as early warnings of
damage to a community or an ecosystem.

Presence or absence of trout species because
they are sensitive to temperature and oxygen
levels.
Keystone Species: Major Players
 Keystone
species help determine the types
and numbers of other species in a
community thereby helping to sustain it.
Keystone Species
Figures 7-4 and 7-5
Foundation Species:
Other Major Players
 Expansion
of keystone species category.
 Foundation
species can create and enhance
habitats that can benefit other species in a
community.

Elephants push over, break, or uproot trees,
creating forest openings promoting grass growth
for other species to utilize.
Case Study:
Why are Amphibians Vanishing?
 Frogs
serve as indicator species because
different parts of their life cycles can be easily
disturbed.
Figure 8-3
Adult frog
(3 years)
Sperm
Young frog
Tadpole develops
into frog
Sexual
Reproduction
Eggs
Tadpole
Fertilized egg
Egg hatches
development Organ formation
Fig. 7-3, p. 147
Case Study:
Why are Amphibians Vanishing?
 Habitat
loss and fragmentation.
 Prolonged drought.
 Pollution.
 Increases in ultraviolet radiation.
 Parasites.
 Viral and Fungal diseases.
 Overhunting.
 Natural immigration or deliberate introduction
of nonnative predators and competitors.
Section 8-3
Species Interactions:
Competition & Predation
Lion vs. Wildebeest
Question of the Day
 Which
of the following is the best example of
a keystone species?
a.
Sea otter
b.
Sea urchin
c.
Spotted owl
d.
Snail darter
e.
E. Condor
SPECIES INTERACTIONS:
COMPETITION AND PREDATION
 Species
can interact through competition,
predation, parasitism, mutualism, and
commensalism.
 Some
species have adaptations that allow
them to reduce or avoid competition for
resources with other species (resource
partitioning).
Competition:
Resource Partitioning
 Each
species minimizes
competition with the others
for food by
1. Spending at least half its
feeding time in a distinct
portion of the spruce tree and
2. By consuming somewhat
different insect species.
Figure 7-7
Competition: Niche Specialization
 Niches
become
separated to
avoid competition
for resources
Grizzlies & Wolves
Figure 7-6
PREDATION
 Species
called predators feed on other
species called prey.
 Organisms
use their senses their senses to
locate objects and prey and to attract
pollinators and mates.
 Some
predators are fast enough to catch their
prey, some hide and lie in wait, and some
inject chemicals to paralyze their prey.
Prey adaptations
1. Some prey escape their
predators
Cheetah vs. Gazelle
2. Have outer protection
3. Some are camouflaged
4. Some use chemicals to
repel predators.
Figure 7-8
(a) Span worm
Fig. 7-8a, p. 153
(b) Wandering leaf insect
Fig. 7-8b, p. 153
(c) Bombardier beetle
Fig. 7-8c, p. 153
(d) Foul-tasting monarch butterfly
Fig. 7-8d, p. 153
(e) Poison dart frog
Fig. 7-8e, p. 153
(f) Viceroy butterfly mimics
monarch butterfly
Fig. 7-8f, p. 153
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
Fig. 7-8g, p. 153
(h) When touched, snake
caterpillar changes shape
to look like head of snake.
Fig. 7-8h, p. 153
Section 8-3
Summary

Competition

Predation
Section 8-4
SPECIES INTERACTIONS:
PARASITISM, MUTUALISM, AND
COMMENSALIM
Tongue Eaters
Question of the Day
Zero population growth is associated with
a. Phase I only
b. Phase II only
c. Phase III only
d. Phase IV only
e. Phase I and IV
PARASITISM, MUTUALISM, AND
COMMENSALIM
 Parasitism
occurs when one species feeds
on part of another organism.
 In
mutualism, two species interact in a way
that benefits both.
 Commensalism
is an interaction that benefits
one species but has little, if any, effect on the
other species.
Parasites: Sponging Off of Others
 Although
parasites can harm their hosts, they
can promote community biodiversity.
1. Some parasites live in host (micororganisms,
tapeworms).
Malaria
2. Some parasites live outside host (fleas, ticks,
mistletoe plants, sea lampreys).
3. Some have little contact with host (dump-nesting
birds like cowbirds, some duck species)
Mutualism: Win-Win Relationship
 Two
species
can interact in
ways that
benefit both of
them.
Unlikely Travel
Companions
Figure 7-9
(a) Oxpeckers and black rhinoceros
Fig. 7-9a, p. 154
(b) Clownfish and sea anemone
Fig. 7-9b, p. 154
(c) Mycorrhizal fungi on juniper seedlings
in normal soil
Fig. 7-9c, p. 154
(d) Lack of mycorrhizal fungi on juniper seedlings
in sterilized soil
Fig. 7-9d, p. 154
Commensalism: Using without Harming
 Some
species
interact in a way
that helps one
species but has
little or no effect
on the other.
Figure 7-10
Section 8-4
Summary
 Parasitism
 Mutualism
 Commensalism
Section 8-5 & 8-6
Ecological Succession
& Stability
Essential Question:
How do communities undergo natural change?
Mt St Helens
Question of the Day
 Which
of the following elements is most likely
to limit primary production in freshwater
lakes?
A. Oxygen
B. Calcium
C. Phosphorus
D. Carbon
E. Iron
COMMUNITIES IN TRANSITION
 New
environmental conditions allow one
group of species in a community to replace
other groups.
 Ecological
succession: the gradual change
in species composition of a given area


Primary succession: the gradual establishment
of biotic communities in lifeless areas where
there is no soil or sediment.
Secondary succession: series of communities
develop in places containing soil or sediment.
Primary Succession:
Starting from Scratch
 Primary
succession
begins with an
essentially lifeless
area, where there
is no soil in a
terrestrial
ecosystem
Figure 7-11
Typical Changes

Community changes during succession include
increases in species diversity and changes in
species composition
•Characteristics of Pioneer Species:

Ecosystem changes during succession include
increases in biomass, primary production,
respiration, and nutrient retention.
•Modification of soil and other environmental
changes lead to changes in species.
Secondary Succession:
Starting Over with Some Help
 Secondary
succession
begins in an
area where
the natural
community
has been
disturbed.
Figure 7-12
Can We Predict the
Path of Succession
 The
course of succession cannot be
precisely predicted.
 Previously
thought that a stable climax
community will always be achieved.
 Succession
involves species competing for
enough light, nutrients and space which will
influence it’s trajectory.
ECOLOGICAL STABILITY AND
SUSTAINABILITY
 Living
systems maintain some degree of
stability through constant change in response
to environmental conditions through:



Inertia (persistence): the ability of a living system
to resist being disturbed or altered.
Constancy: the ability of a living system to keep
its numbers within the limits imposed by available
resources.
Resilience: the ability of a living system to
bounce back and repair damage after (a not too
drastic) disturbance.
ECOLOGICAL STABILITY AND
SUSTAINABILITY
 Having
many different species appears to
increase the sustainability of many
communities.
 Human
activities are disrupting ecosystem
services that support and sustain all life and
all economies.
Chapter Overview Questions

What determines the number of species in a
community?

How can we classify species according to their
roles in a community?

How do species interact with one another?

How do communities respond to changes in
environmental conditions?

Does high species biodiversity increase the stability
and sustainability of a community?