# Community Ecology - PowerPoint PPT Presentation

1 / 69
Title:

## Community Ecology

Description:

### Community Ecology Community Ecology AP Chapter 54 AP Chapter 54 – PowerPoint PPT presentation

Number of Views:327
Avg rating:3.0/5.0
Slides: 70
Provided by: charlot126
Category:
Tags:
Transcript and Presenter's Notes

Title: Community Ecology

1
Community Ecology
Community Ecology
AP Chapter 54
• AP Chapter 54

2
Calculator Policy
• A four-function calculator (with square root) is
permitted on both the multiple-choice and
free-response sections of the AP Biology Exam
since both sections contain questions that
require data manipulation. No other types of
calculators, including scientific and graphing
calculators, are permitted for use on the exam.
Four-function calculators have a one line display
and a simple layout of numeric keys (e.g., 09),
arithmetic operation keys (e.g., , -, , and ),
and a limited number of special-use keys (e.g.,
, /-, C, and AC). Simple memory buttons like
MC, M, M-, and MR may also be included on a
four-function calculator. Scientific calculators
have a more complicated, multi-row layout that
includes various special-use keys, including ones
for trigonometric and logarithmic functions such
as SIN, COS, TAN, TRIG, LOG, and LN. In contrast
to scientific calculators, four-function
calculators do not include trigonometric and
logarithmic functions, statistical capabilities,
or graphing capabilities. Students may bring up
to two four-function calculators (with square
root) to the exam.

3
What is a community?
• A biological community is an assemblage of
populations of various species living close
enough for potential interaction

4
What are the types of interactions?
• relationships between species in a community
interspecific interactions
• Examples are competition, predation, herbivory,
and symbiosis (parasitism, mutualism, and
commensalism)
• Interspecific interactions can affect the
survival and reproduction of each species, and
the effects can be summarized as positive (),
negative (), or no effect (0)

5
Competition
• Interspecific competition (/ interaction)
occurs when species compete for a resource in
short supply
• Strong competition can lead to competitive
exclusion, local elimination of a competing
species
• The Gause competitive exclusion principle states
that two species competing for the same limiting
resources cannot coexist in the same place

6
Ecological Niches
• The total of a species use of biotic and abiotic
resources is called the species ecological niche
• An ecological niche can also be thought of as an
organisms ecological role
• It is the functional position of an organism in
its environment, comprising its habitat and the
resources it obtains, periods of time it is
active, etc.

7
Adaptations for Locomotion Biorhythms Tolerance Pr
edator avoidance Reproduction feeding
Physical conditions Substrate Humidity Sunlight Te
mperature Salinity pH Exposure Attitude depth
Resources offered by the habitat Food Shelter Mati
ng sites Nesting sites Predator avoidance
Other organisms
8
• Ecologically similar species can coexist in a
community if there are one or more significant
differences in their niches
• Resource partitioning is differentiation of
ecological niches, enabling similar species to
coexist in a community

9
Fig. 54-2
A. insolitus usually perches on shady branches.
A. distichus perches on fence posts and other
sunny surfaces.
A. ricordii
A. insolitus
A. aliniger
A. christophei
A. distichus
A. cybotes
A. etheridgei
10
• The full range of environmental conditions under
which an organism can exist is its fundamental
niche.
• Due to interactions and evironmental pressures,
organisms are usually forced to occupy a niche
that is narrower than thistheir realized niche.

11
Fig. 54-3
EXPERIMENT
High tide
Chthamalus
Chthamalus realized niche
Balanus
Balanus realized niche
Ocean
Low tide
RESULTS
High tide
Chthamalus fundamental niche
Ocean
Low tide
12
• Question Two species of Anolis lizards are
often found perched and feeding in the same
trees, with species I in the upper and outer
branches, and species II occupying the shady
inner branches. After removing one or the other
species in test trees, an ecologist observes the
following results Species I is found throughout
the branches of trees in which it is now the sole
occupant. Species II is still found only in the
shady interior when it is the sole occupant.
What do these results indicate about the niches
of these two species?

The realized niche of Species I is smaller than
its fundamental niche when it is in competition
with SpeciesII.
Species I
Species IIs fundamental and Realized niche are
the same.
Species II
13
Predation
• Predation (/ interaction) refers to interaction
where one species, the predator, kills and eats
the other, the prey
• Some feeding adaptations of predators are claws,
teeth, fangs, stingers, and poison
• Prey display various defensive adaptations -
hiding, fleeing, forming herds or schools,
self-defense, coloration patterns, mimicry, and
alarm calls

14
Predator-Prey Graph
Lag time Peak to peak or Trough to trough
months
15
Coloration Patterns and Mimicry
16
Herbivory
• Herbivory (/ interaction) refers to an
interaction in which an herbivore eats parts of a
plant or alga
• It has led to evolution of plant mechanical and
chemical defenses and adaptations by herbivores

17
Fig. 54-6
A manatee is feeding on water hyacinth, an
introduced species, in Florida.
18
Symbiosis
• Symbiosis is a relationship where two or more
species live in direct and intimate contact with
one another
• parasitism (/ interaction)
• mutualism (/ interaction), is an interspecific
interaction that benefits both species
• A mutualism can be
• Obligate, where one species cannot survive
without the other
• Facultative, where both species can survive alone
• commensalism (/0 interaction)

19
Fig. 54-7
The tree and the ant are locked into relationship
where the survival of both partners depends on
the other. The ants provide the Acacia with
protection from herbivores and from competing
plants, while the tree provides the ants with
food and shelter. Facultative mutualism
(a) Acacia tree and ants (genus Pseudomyrmex)
(b) Area cleared by ants at the base of an acacia
tree
20
Clownfish and Sea Anemones
Facultative Mutualism
21
Fig. 54-8
Facultative Mutualism
22
Parasitism
23
Commensalism epiphytes
24
protists in termite guts
Obligate Mutualism
25
• In general, a few species in a community exert
strong control on that communitys structure
• Two fundamental features of community structure
are species diversity and feeding relationships

26
Species Diversity
• Species diversity of a community is the variety
of organisms that make up the community
• It has two components species richness and
relative abundance
• Species richness is the total number of different
species in the community
• Relative abundance is the proportion each species
represents of the total individuals in the
community

27
Fig. 54-9
A
B
C
D
Community 1
Community 2
A 80 B 5 C 5 D 10
A 25 B 25 C 25 D 25
Two communities can have the same species
richness but a different relative abundance
28
• Shannon Diversity Formula
• H' - S pi ln pi
• Where pi the proportion of individuals of
species i.
the summation sign.

Species   No. of Individuals  pi  ln pi
Beech 32  32  __     0.52   62  -0.65
Maple 18  18  __     0.29   62  -1.24
Oak 12  12  __     0.19   62  -1.66
Total 62
29
• H' - (0.52 X -0.65) (0.29 X -1.24) (0.19 X
-1.66)
• H' -(-0.338) (-0.360) (-0.315)
• H' -(-1.01) 1.01

30
Trophic Structure
• Trophic structure is the feeding relationships
between organisms in a community
• It is a key factor in community dynamics
• Food chains link trophic levels from producers to
top carnivores

31
Fig. 54-11
Quaternary consumers
Carnivore
Carnivore
Tertiary consumers
Carnivore
Carnivore
Secondary consumers
Carnivore
Carnivore
Primary consumers
Herbivore
Zooplankton
Primary producers
Plant
Phytoplankton
A terrestrial food chain
A marine food chain
32
A food web is a branching food chain with complex
trophic interactions
Fig. 54-12
Humans
Smaller toothed whales
Baleen whales
Sperm whales
Elephant seals
Leopard seals
Crab-eater seals
Fishes
Squids
Birds
Carnivorous plankton
Copepods
Euphausids (krill)
Phyto- plankton
33
Limits on Food Chain Length
• Two hypotheses attempt to explain food chain
length
• The energetic hypothesis suggests that length is
limited by inefficient energy transfer
• The dynamic stability hypothesis proposes that
long food chains are less stable than short ones
• Most data support the energetic hypothesis

34
Experimental data from the tree hole communities
showed that food chains were longest when food
supply (leaf litter) was greatest. Which
hypothesis about what ali its food chain length
do these results suggest?
energetic
35
Fig. 54-14
5
4
3
2
1
0
High (control) natural rate of litter fall
Medium 1/10 natural rate
Low 1/100 natural rate
Productivity
36
Species with a Large Impact
• Certain species have a very large impact on
community structure
• Such species are highly abundant or play a
pivotal role in community dynamics
• Dominant species are those that are most abundant
or have the highest biomass (the total mass of
all individuals in a population)

37
Why are they dominant?
• One hypothesis suggests that dominant species are
most competitive in exploiting resources
• Another hypothesis is that they are most
successful at avoiding predators

38
Invasive Species
• Species typically introduced to a new environment
by humans, often lack predators or disease

39
Kudzu
• Kudzu is a vine which was brought to North
America from Asia in 1876 to help prevent soil
erosion, which has since become an utter nuisance
in some areas of the country. It can grow up to
6.5 feet a week and its roots are nearly

40
Other examples
• Dutch Elm Disease caused by a fungus and
accidentally spread into the United States.
• Potato Blight caused by a fungus that caused
the Great Potato Famine in Ireland in the 1840s.
Spores have been carried all over the world.
• Small Pox spread of virus from Asia to all over
the world.

Dutch Elm Disease
41
• Dutch elm disease (DED) is caused by a member of
the sac fungi (Ascomycota) affecting elm trees,
and is spread by the elm bark beetle. Although
believed to be originally native to Asia, the
disease has been accidentally introduced into
America and Europe, where it has devastated
opportunity to evolve resistance to the disease.
The name "Dutch elm disease" refers to its
identification in 1921 in the Netherlands by
Dutch phytopathologists.

42
Potato Blight caused by a fungus.
Smallpox caused by a virus.
43
Keystone Species
• Keystone species exert strong control on a
community by their ecological roles, or niches
• In contrast to dominant species, they are not
necessarily abundant in a community

44
Fig. 54-15
EXPERIMENT
Field studies of sea stars exhibit their role as
a keystone species in intertidal
communities They keep the number of mussels
controlled that outcompete other species.
RESULTS
20
With Pisaster (control)
15
Number of species present
10
Without Pisaster (experimental)
5
0
1963
64
65
66
67
68
69
70
71
72
73
Year
45
Fig. 54-16
100
80
Otter number ( max. count)
60
40
20
Observation of sea otter populations and their
predation shows how otters affect ocean
communities
Keystone species
0
(a) Sea otter abundance
400
After orcas entered the food chain and preyed
on the otters, notice the change in the sea
urchins and kelp.
300
Grams per 0.25 m2
200
100
0
(b) Sea urchin biomass
10
8
Number per 0.25 m2
6
4
2
0
1972
1985
1997
1989
1993
Year
(c) Total kelp density
Food chain
46
This resulted in a loss of kelp forests.
47
Ecological Succession
• Ecological succession is the sequence of
community and ecosystem changes after a
disturbance
• Primary succession occurs where no soil exists
when succession begins
• Secondary succession begins in an area where soil
remains after a disturbance

48
(No Transcript)
49
Successive species can
• Inhibit growth of new organisms
• sphagnum moss making boggy areas
• in poorly drained sites
• Promote growth of new organisms
• Dryas and Alder trees raising N content
• Tolerate conditions that resulted from former
species

50
Fig. 54-22-4
Succession on the moraines in Glacier Bay,
Alaska, follows a predictable pattern of change
in vegetation and soil characteristics
1941
1907
Dryas stage
2
Pioneer stage, with fireweed dominant
1
5
10
15
0
Kilometers
1860
Glacier Bay
1760
Alder stage
3
Spruce stage
4
51
Succession at Mt. St. Helens in 1980
52
• Pioneer stage first species
• Climax or dominant species stable, typically
most biomass species

Mosses - pioneers
Hardwood Forests - dominant
53
Fig. 54-23
60
Succession is the result of changes induced by
the vegetation itself. On the glacial moraines,
vegetation lowers the soil pH and increases soil
nitrogen content.
50
40
Soil nitrogen (g/m2)
30
20
10
0
Pioneer
Dryas
Alder
Spruce
Successional stage
54
Dune Succession
Primary Succession
55
(No Transcript)
56
Pond Succession
Secondary succession
57
Human Disturbance
• Humans have the greatest impact on biological
communities worldwide!
• Human disturbance to communities usually reduces
species diversity
• Humans also prevent some naturally occurring
disturbances, which can be important to community
structure

58
Fig. 54-24
Results from trawling.
59
Biogeographic factors affect community
biodiversity
• Latitude and area are two key factors that affect
a communitys species diversity
• - generally declines along an
equatorial-polar gradient and is especially great
in the tropics
• - two key factors are evolutionary history
and climate
• The greater age of tropical environments may
account for the greater species richness more
growing time so more chance for evolutionary
changes

60
Area Effects
• The species-area curve quantifies the idea that,
all other factors being equal, a larger
geographic area has more species
• A species-area curve of North American breeding
birds supports this idea

61
Fig. 54-26
1,000
100
Number of species
10
1
0.1
1
10
100
103
104
105
106
107
108
109
1010
Area (hectares)
62
Island Equilibrium Model
• Species richness on islands depends on island
size, distance from the mainland, immigration,
and extinction

63
• The number of species found on an island can
be determined by a balance between the
immigration rate (or the movement of species onto
the island from other islands) and the extinction
rate (or the rate at which species already on the
island become nonexistent).

64
Effect of Island Size
Immigration and extinction rates are affected by
the size of the island and its distance from a
non-island source of immigrant species
A larger island has higher species diversity for
two reasons it is a larger target, giving it a
greater probability of becoming the home to
immigrants, and it has a larger supply of
resources necessary to prevent extinctions.
65
Effect of Island Distance
• An island's distance from a mainland source of
new immigrants, despite its size, is an important
factor in species diversity. Even if two islands
are the exact same size and all other factors are
constant, the island closest to the mainland is
more likely to attract a larger number of
immigrant species due to its proximity and
convenience

66
Fig. 54-28
Studies of species richness on the Galápagos
Islands support the prediction that species
richness increases with island size
400
200
100
50
Number of plant species (log scale)
25
10
5
10
100
103
104
105
106
Area of island (hectares) (log scale)
67
Community ecology is useful for understanding
pathogen life cycles and controlling human disease
• Ecological communities are universally affected
by pathogens, which include disease-causing
microorganisms, viruses, viroids (viral DNA), and
prions (proteins)

68
Fig. 54-30
• Avian flu is a highly contagious virus of birds
• Ecologists are studying the potential spread of
the virus from Asia to North America through
migrating birds

69
Pathogens can alter community structure quickly
and extensively
For example, coral reef communities are being
decimated by white-band disease
70
• Human activities are transporting pathogens
around the world at unprecedented rates
• Community ecology is needed to help study and
combat them
• Zoonotic pathogens have been transferred from
other animals to humans
• The transfer of pathogens can be direct or
through an intermediate species called a vector
• Many of todays emerging human diseases are
zoonotic SWINE FLU!