Post on 27-Jun-2020
Community structure, succession
What is Community Structure? Physical appearance
Relative sizes, stratification, and distribution of its populations and species.
Species diversity and richness The number of different species
Species abundance The number of individuals of each species
Niche structure The number of ecological niches, their resemblance,
and how they interact
m ft
10
50
20
30
100
Tropical rain forest
Coniferous forest
Deciduous forest
Thorn forest
Tall-grass prairie
Short-grass prairie
Desert scrub
Thorn scrub
Types, sizes, and stratification of plant species in terrestrial
communities
Mosaic of vegatation patches
•Ecotones – transition zones
between ecosystems
•Edge Effects - differences in
the physical structure and
physical properties between
two ecosystems
•Riparian Zone- the thin strip
or patch of vegetation
surrounding a stream.
Important habitat/resource
areas
Species Diversity Most Species Rich Environments
Major factors affecting species diversity
Tropical Rainforest
Coral Reefs
The deep sea
Large Tropical Lake
Latitude
Depth
Pollution
10
Sp
eci
es
Div
ers
ity
1,000
100
Latitude
80ºN 60 40 20 0
Sp
eci
es
Div
ers
ity
200
100
0
90ºN 60 30 0 30ºS 60
Latitude
latitudinal species diversity gradient
0 0
Sp
eci
es
div
ers
ity
25
20
15
5
10
0 2,000 4,000 6,000
Depth (meters)
2,000 4,000 6,000
Depth (meters)
25
20
15
5
10
0
Coast Deep Sea Coast Deep Sea
Snails Tube worms
Depth
Number of individuals per diatom species
Nu
mb
er
of
dia
tom
sp
eci
es
Unpolluted stream
Polluted stream
Pollution
What determines the number of
species in an isolated ecosystem?
Island Ecosystems
Size of the ecosystem
Degree of isolation
Species Equilibrium Model or
Theory of Island Biogeography (MacArthur and Wilson)
Number of species found on an island determined by balance between:
Rate of immigration
Rate of extinction
Immigration and extinction rates effected by:
Size of island
Distance from nearest mainland
High
Low
Ra
te o
f im
mig
rati
on
o
r e
xti
nct
ion
Immigration and extinction rates
Number of species on island
(a)
© 2004 Brooks/Cole – Thomson Learning
Equlibrium point
High
Low
Ra
te o
f im
mig
rati
on
o
r e
xti
nct
ion
Small island
Effect of island size
Number of species on island
(b)
Large island
High
Low
Ra
te o
f im
mig
rati
on
o
r e
xti
nct
ion
Far island
Effect of distance from mainland
Number of species on island
(c)
Near island
© 2004 Brooks/Cole – Thomson Learning
100
50
25
12.5
6.25
0 2,000 4,000 6,000 8,000 10,000
Distance from New Guinea (kilometers)
Nu
mb
er
of
spe
cie
s (p
erc
en
tag
e o
f sa
mp
le s
tud
ied
)
NEW GUINEA
© 20
04
Bro
ok
s/Co
le –
Th
om
son
Le
arn
ing
Species diversity decreases with increasing distance
100
1 10 100 1,000 10,000 100,000
Area (square miles)
Nu
mb
er
of
am
ph
ibia
n a
nd
re
pti
le s
pe
cie
s
10
SABA MONTSERRAT CUBA
Hispaniola
Puerto Rico
Jamaica
Cuba
Montserrat
Saba
Redonda
© 20
04
Bro
ok
s/Co
le –
Th
om
son
Le
arn
ing
Species diversity increases with increasing island size
Roles of Species in Ecosystems
native
non-native
indicator
Keystone
Foundation
Native and Non-native Species Native species
Species that normally live and thrive in a
particular ecosystem
Non-native (exotic or alien) species
Species that migrate into an ecosystem or are
deliberately or accidentally introduced into an
ecosystem
Cane toads
Feral Hogs
Indicator Species Species that serve as early warning of damage
to a community or an ecosystem (most
sensitive)
Birds
Fish
Amphibians
Habitat
loss/degradation
Drought
Pollution
UV radiation
Parasitism
Over-hunting
Diseases
Immigration or
introduction of
predators or
competitors
sperm
Eggs
Sexual reproduction
Fertilized egg development
Organ formation
Egg hatches
Tadpole
Tadpole develops Into frog
Young frog
Adult frog (3 years)
Indicators of things like . .
Keystone Species Species that play roles affecting many other
organisms in an ecosystem Strong interaction with other species affect health and
survival of species
Process material out of proportion to their numbers or biomass
Pollination
Seed dispersion
Habitat modification
Predation by top carnivores
Recycling of plant and animal waste
Example: American Alligator
Foundation Species Species that play a major role in shaping their
communities by creating and enhancing their habitats in ways that benefit other species.
Elephants—create openings in woodlands
Beaver- build dams to create ponds and wetlands
Fruit bats—deposit seeds in droppings to help regenerate forests
What is the major difference between Foundation and Keystone species?
Species Interactions competition
predation
parasitism
mutualism
commensalism
Competition Intraspecific competition – competition between
members of the same species
Gain a competitive advantage (Plants)
Chemical inhibitors
Seed dispersal
Territoriality (Animals)
Patrol or mark an area
Defend an area
Competition Interspecific competition – competition
between members of two or more different
species
Abundant commonly used resources (food,
sunlight, water, soil nutrients, space, nesting
sites)
Fundamental niche
Limited resources
Overlap of fundamental niches
Interspecific Competition Interference competition
One species limits another’s access to some
resources
Exploitation competition
Competing species have equal access to
resources but differ in how fast or efficiently they
exploit it
Competitive Exclusion Principle
The niches of two species cannot overlap completely or significantly for very long.
Nu
mb
er
of
ind
ivid
ua
ls
Nu
mb
er
of
ind
ivid
ua
ls
Resource use
Resource use
Species 1 Species 2
Region of
niche overlap
Species 1 Species 2
Resource Partitioning
Niche Specialization
Resource Partitioning
Each species minimizes competition with the others for food by spending at least half its feeding time in a distinct portion of the spruce tree and by consuming somewhat different insect species.
Predator – Prey Relationship Predation – members of one species (predator)
feed directly on all or part of a living organism of another species (prey).
Benefits from reducing prey population
Gives remaining prey greater access to food supply
Can improve the genetic stocks of the prey population
Predator Tactics Pursuit vs….
Pursuit: Cheetah, wolves,eagles.
Ambush: owls, preying mantis, humans
Ambush
Prey Tactics Run, swim, or fly fast
Highly developed
sense of sight or
smell
Protective shells
Thick bark
Spines or thorns
Chemical defenses
Camouflage
Warning coloration
Mimicry
Behavioral strategies
Span worm Bombardier beetle
Viceroy butterfly Mimics monarch butterfly
Foul-tasting monarch butterfly
Poison dart frog
When touched, the snake caterpillar changes shape to look like the head of a snake
Wandering leaf insect
Hind wings of io Moth resemble eyes of a much larger animal
Symbiotic Species Interactions Symbiosis – relationship in which species live
together in an intimate association.
Parasitism
Mutualism
Commensalism
Parasitism One species (parasite) feeds on part of another
organism (host) by living on or in the host.
Smaller than the host
Remains closely associated with host and may
weaken host over time
Rarely kills its host
Mutualism Two species interact in ways that benefit both
Nutritional mutualism
Pollination, lichens, rhizobium, coral, bacteria
Nutrition and protection
Birds and large animals, clownfish and anemones,
mycorrihizae and plants
Figure 8-12 Page 179
Oxpeckers and black rhinoceros Clown fish and sea anemone
Lack of mycorrhizae fungi on juniper seedlings in normal soil
Mycorrhizae fungi on juniper seedlings in sterilized soil
Commensalism
symbiotic
relationship that
benefits one
species but
neither harms nor
helps the other
species
Ecological Succession - the gradual change in species composition in a
given area
Primary Succession – gradual establishment of biotic communities on nearly lifeless ground
Secondary Succession – reestablishment of biotic communities in an area where some type of biotic community is already present
Small herbs and shrubs
Heath mat
Jack pine, black spruce,
and aspen
Balsam fir, paper birch, and
white spruce climax community
Time
Exposed rocks
Lichens and mosses
Primary Ecological
Succession
Pioneer
species
Early
successional
Mid-
successional
Late
Successional or
Climax
Community
Time Annual weeds
Perennial weeds and
grasses
Shrubs Young pine forest
Mature oak-hickory forest
Secondary
Ecological
Succession
Midsuccessional
Species
Elk
Moose
Deer
Ruffled grouse
Snowshoe hare
Bluebird
Late Successional
Species
Turkey
Martin
Hammond’s
flycatcher
Gray squirrel
Wilderness
Species
Grizzly bear
Wolf
Caribou
Bighorn sheep
California condor
Great horned owl
Early Successional
Species
Rabbit
Quail
Ringneck pheasant
Dove
Bobolink
Pocket gopher
Ecological succession
© 2004 Brooks/Cole – Thomson Learning
Ecological Succession of Wildlife
Species
Changes Affecting Ecosystems Catastrophic
Natural Drought
Flood
Fire
Volcanic eruption
Earthquake
Hurricane
Landslide
Disease
Human-caused Deforestation
Overgrazing
Plowing
Erosion
Pesticide application
Fire
Mining
Urbanization
Water and air pollution
Loss and degradation of wildlife habitat
Gradual
Natural Climate change
Immigration
Adaptation and evolution
Ecological succession
Disease
Human-caused Salinization
Soil compaction
Groundwater depletion
Water and air pollution
Loss and degradation of wildlife habitat
Introduction of nonnative species
Overhunting and overfishing
Toxic contamination
Urbanization
Excessive tourism
Predictability and the
Balance of Nature Old Concept
Succession
Climax Community
New Concept
Biotic change
Mature community or
vegetative patches
100 0
Percentage disturbance
Sp
ec
ies
div
ers
ity
Intermediate
disturbance
hypothesis
Stability – the ability of living systems to
withstand or recover from externally
imposed changes or stresses.
Inertia – ability to resist being disturbed
Constancy – keep numbers within limits
Resilience – ability to bounce back
Precautionary Principle When evidence indicates an activity can harm
human health or the environment, we should take precautionary measures to prevent harm even if some of the cause-and-effect relationships have not been fully established scientifically.
Grizzly bear
NORTH AMERICA
Spotted owl
Black- footed ferret
Kemp’s ridley turtle
California condor
Golden toad
Columbia has lost one-third of its forest
Black lion tamarin
SOUTH AMERICA
More than 60% of the Pacific Northwest coastal forest has been cut down
40% of North America’s range and cropland has lost productivity
Hawaiian monk seal
Half of the forest in Honduras and Nicaragua has disappeared
Mangroves cleared in Equador for shrimp ponds
Southern Chile’s rain forest is threatened
Little of Brazil’s Atlantic forest remains
Every year 14,000 square kilometers of rain forest is destroyed in the Amazon Basin
Coral reef destruction
Much of Everglades National Park has dried out and lost 90% of its wading birds
ATLANTIC OCEAN
PACIFIC OCEAN
Manatee
Chesapeake Bay is overfished and polluted
Fish catch in the north-west Atlantic has fallen 42% since its peak in 1973
Humpback whale
St. Lawrence beluga whale Eastern
cougar
Florida panther
Environmental degradation
Vanishing biodiversity
Endangered species
EUROPE
Mediterranean
Liberia
AFRICA
Imperial eagle
640,000 square kilometers south of the Sahara have turned to desert since 1940
Mali
Burkina Faso
Sierra Leone
Togo Sao Tome
68% of the Congo’s rain forest is slated for cleaning
Fish catches in Southeast Atlantic have dropped by more than 50% since 1973 Black
rhinoceros
Zambia
Angola
Congo Rwanda Burundi
Uganda Somalia
Nigeria
Chad Niger Benin Golden
tamarin
Ethiopia
Eritrea
Madagascar has lost 66% of its tropical forest
Aye-aye
Yemen Oman
Saudi Arabia
Poland is one of the world’s most polluted countries
Many parts of former Soviet Union are polluted with industrial and radio- active waste
Area of Aral Sea has Shrunk 46%
Central Asia from the Middle East to China has lost 72% of range and cropland
ASIA
Asian elephant
India and Sri Lanka have almost no rain forest left
In peninsular Malaysia almost all forests have been cut
INDIAN OCEAN
Indonesia’s coral reefs are threatened and mangrove forests have been cut in half
Giant panda
Kouprey
Queen Alexandra’s Birdwing butterfly
Nail-tailed wallaby
AUSTALIA
Much of Australia’s range and cropland have turned to desert
90% of the coral reefs are threatened in the Philippines. All virgin forest will be gone by 2010
Deforestation in the Himalaya causes flooding in Bangladesh
Japanese timber imports are responsible for much of the world’s tropical deforestation
Blue whale
ANTARCTICA
A thinning of the ozone layer occurs over Antarctica during summer
Snow leopard
6.0 or more children per woman
Species Diversity Two factors define species diversity:
Species Richness
Number of species in the community.
Species Evenness
Relative abundance of species.
Species Diversity
Environmental Complexity In general, species diversity increases with
environmental complexity or heterogeneity.
Many studies have shown positive relationship between environmental complexity and species diversity.
Environmental Complexity
Quantitative Index of Species Diversity Shannon Wiener Index:
s
H’ = -∑pi logepi
i=l
H’ = Value of SW diversity index.
pi = Proportion of the ith species.
loge = Natural logarithm of pi.
s = Number of species in community.