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Title: Community Ecology


1
Chapter 8
  • Community Ecology

Importance of Biodiversity
2
Question of the Day
  • The best example of a tertiary consumer would be
    a/an
  • mouse
  • grasshopper
  • sheep
  • cactus
  • coyote

3
Section 8-1
  • Community Structure
  • Species Diversity
  • Question to Consider
  • How does community structure affect species
    diversity?

4
COMMUNITY STRUCTURE
  • Biological communities differ in their structure
    and physical appearance.

Figure 8-2
5
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.

6
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).

7
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.

8
Species Diversity on Islands
  • MacArthur and Wilson proposed the species
    equilibrium model or theory of island
    biogeography in the 1960s.
  • 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
9
Section 8-2
  • Types of Species
  • Question to Consider
  • How does a species role affect biological
    communities?

10
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

11
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
12
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.

13
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
14
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.

15
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
16
Adult frog(3 years)
Young frog
Sperm
Tadpole develops into frog
Sexual Reproduction
Tadpole
Eggs
Fertilized egg development
Egg hatches
Organ formation
Fig. 7-3, p. 147
17
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.

18
Section 8-3
  • Species Interactions
  • Competition Predation
  • Lion vs. Wildebeest

19
Question of the Day
  • Which of the following is the best example of a
    keystone species?
  • Sea otter
  • Sea urchin
  • Spotted owl
  • Snail darter
  • E. Condor

20
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).

21
CompetitionResource 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
22
Competition Niche Specialization
  • Niches become separated to avoid competition for
    resources
  • Grizzlies Wolves

Figure 7-6
23
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.

24
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
25
(a) Span worm
Fig. 7-8a, p. 153
26
(b) Wandering leaf insect
Fig. 7-8b, p. 153
27
(c) Bombardier beetle
Fig. 7-8c, p. 153
28
(d) Foul-tasting monarch butterfly
Fig. 7-8d, p. 153
29
(e) Poison dart frog
Fig. 7-8e, p. 153
30
(f) Viceroy butterfly mimics monarch
butterfly
Fig. 7-8f, p. 153
31
(g) Hind wings of Io moth resemble eyes of
a much larger animal.
Fig. 7-8g, p. 153
32
(h) When touched, snake caterpillar changes
shape to look like head of snake.
Fig. 7-8h, p. 153
33
Section 8-3
  • Summary
  • Competition
  • Predation

34
Section 8-4
SPECIES INTERACTIONS PARASITISM, MUTUALISM, AND
COMMENSALIM
Tongue Eaters
35
Question of the Day
  • Zero population growth is associated with
  • Phase I only
  • Phase II only
  • Phase III only
  • Phase IV only
  • Phase I and IV

36
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.

37
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)

38
Mutualism Win-Win Relationship
  • Two species can interact in ways that benefit
    both of them.
  • Unlikely Travel Companions

Figure 7-9
39
(a) Oxpeckers and black rhinoceros
Fig. 7-9a, p. 154
40
(b) Clownfish and sea anemone
Fig. 7-9b, p. 154
41
(c) Mycorrhizal fungi on juniper seedlings in
normal soil
Fig. 7-9c, p. 154
42
(d) Lack of mycorrhizal fungi on juniper
seedlings in sterilized soil
Fig. 7-9d, p. 154
43
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
44
Section 8-4Summary
  • Parasitism
  • Mutualism
  • Commensalism

45
Section 8-5 8-6
  • Ecological Succession
  • Stability
  • Essential Question
  • How do communities undergo natural change?
  • Mt St Helens

46
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

47
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.

48
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
49
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.

50
Secondary Succession Starting Over with Some
Help
  • Secondary succession begins in an area where the
    natural community has been disturbed.

Figure 7-12
51
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
    its trajectory.

52
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.

53
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.

54
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?
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