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Community Ecology

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Title: Community Ecology


1
Community Ecology
CHAPTER 8
  • Structure
  • Species Interaction
  • Succession Sustainability

2
Key Concepts
  • Community structure
  • Roles of species
  • Species interactions
  • Changes in ecosystems
  • Stability of ecosystems

3
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)

4
COMMUNITY STRUCTURE
OBJ 8.1
  • CHARACTERISTICS
  • Physical Appearance
  • - stratification, relative size, distribution
  • Species Diversity
  • - richness vs. eveness
  • Niche Structure
  • - ecological Roles of Species

5
Community Structure Appearance and Species
Diversity
  • Stratification

Fig. 8-2p. 144
6
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.
7
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 _at_ 2000 m then begins its decrease
  • Pollution- as levels increase, biodiversity
    decreases

8
Figure 8-4 Page 145
Number of individuals per diatom species
9
Island Biodiversity
  • Theory of Island Biogeography-the number of
    species found on an island is determined by
  • Species immigration
  • Immigration- movement of organisms into a place
  • Emigration- movement of organisms out of a place
  • Species extinction

10
Island Species
11
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
  • Process out materials out of proportion to their
    numbers or biomass

12
Competition
OBJ 8.3
  • CompetitionTwo organisms compete to obtain the
    same limited resource, and both are harmed to
    some extinct.
  • IntraspecificMembers of same species competing
    for resources.
  • InterspecificMembers of different species
    competing for resources.
  • The more similar the competing species, the more
    intense the competition.

13
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14
Competition
OBJ 8.4
  • Competitive Exclusion PrincipleNo 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.

15
Resource Partitioning
OBJ 8.5
Overlapping Niche of 2 species creates
competition
Over time, species evolve and become specialized
Fig. 8-7 p. 150
16
Kinds of Organism Interactions
  • PredationOne animal kills/eats another.
  • Predator benefits from food.
  • 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.

17
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

18
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19
Symbiotic Relationships
OBJ 8.7
  • SymbiosisClose, physical relationship between
    two different species. At least one species
    derives benefit from the interaction.
  • ParasitismOne organism (parasite) living in or
    on another organism (host), from which it derives
    nourishment.
  • EctoparasitesLive on hosts surface.
  • Fleas
  • EndoparasitesLive inside host.
  • Tapeworms

20
Symbiotic Relationships
  • CommensalismOne organism benefits, while the
    other is unaffected.
  • Remoras and Sharks
  • MutualismBoth species benefit. Obligatory in
    many cases as neither can exist without the
    other.
  • Mycorrhizae

21
WHAT IS HAPPENING?
22
Succession
  • SuccessionA 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 communityStable, long-lasting community,
    primarily determined by climate.

23
Succession
OBJ 8.8
  • Primary SuccessionBegins with bare mineral
    surfaces or water and total lack of organisms.
  • Secondary SuccessionBegins with disturbance of
    an existing ecosystem.
  • Much more commonly observed.

24
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.

25
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) StageEach step in the
    process.

26
Terrestrial Primary Succession
OBJ 8.9
27
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.

28
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.

29
Aquatic Primary Succession
30
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.

31
Terrestrial Secondary Succession
32
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.
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