Download 6. Community Ecology new

Community Ecology
IB: 2.1
Ch. 8
Videos – extinction clip on exotics, clip
on coral reefs
2.1 Species and Populations
• A species is a group of organisms that share common
characteristics and that interbreed to produce fertile offspring.
• A habitat is the environment in which a species normally lives.
• A niche describes the particular set of abiotic and biotic
conditions and resources to which an organism or population
responds.
• The fundamental niche describes the full range of conditions
and resources in which a species could survive and reproduce.
The realized niche describes the actual conditions and
resources in which a species exists due to biotic interactions.
• The interactions between the organisms—such
as predation, herbivory, parasitism, mutualism,
disease, and competition—are termed biotic
factors.
• • Interactions should be understood in terms of
the influences each species has on the
population dynamics of others, and upon the
carrying capacity of the others’ environment.
Vocabulary
•
•
•
•
•
Community
Competition
Mutualism
Niche
Parasitism
Definitions
1.
2.
3.
4.
5.
Population  a group of individuals of a certain
species in a given area at a given time: blue crabs in
the Halifax river
Community  interacting groups of populations in an
area: the scrub community on campus
Species  a group of individuals who can interbreed
to produce fertile, viable offspring: FL panthers
Niche  The role of an organism in its environment
(multidimensional): nocturnal predator of small
mammals in the forest
Habitat  Where an organism typically lives:
mangrove swamps
Community Structure
• Consider the spatial distribution of
organisms
• Physical appearance: Size, stratification,
distribution of populations and species
• Species diversity and richness: number of
different species
• Species abundance: number of individuals
of each species
• Niche structure: number, uniqueness and
interaction of niches available
100
30
20
50
10
ft
m
Tropical
rain forest
Coniferous
forest
Deciduous
forest
Thorn
forest
Thorn
scrub
Tall-grass
prairie
Short-grass
prairie
Comparison of types, sizes and stratification of species
in different terrestrial communities (complexity)
Desert
scrub
Community Differences
• Aquatic systems  deep ocean, sandy beach,
lakes, rivers, wetlands
• Physical structure varies
– Most habitats are mosaics, vegetation patches
– Sharp edges or broad ecotones (transition zones)
– Physical properties differ at edges = edge effect
– Forest edge may be sunnier, drier, warmer
• different species at the edge
• Many wild game species found here
• Edges can fragment habitat  vulnerability & barriers
What is a niche
• The organisms role in its environment
• How it responds to the distribution of
resources
• Many dimensions to it – therefore an ndimensional hypervolume
• No two species can occupy the same
niche for any period of time
• If a niche is vacant organisms will quickly
adapt to fill it
• Fundamental Niche  Everything that the
organism could possibly do given a
competitor free environment
• Realized Niche  Everything the
organism does after competition limits
them
Connell’s
Barnacles
Biodiverse Communities
•
•
•
Top species rich environments are tropical
rainforests, coral reefs, deep sea, large
tropical lakes
Usually high diversity but low abundance
Factors for increased diversity
1. Latitude: most diverse near equator
2. Depth: marine communities peak about 2000m
3. Pollution: more pollution  less species
On land increases in solar radiation, precipitation,
seasonal variation, decreased elevation
1,000
Species Diversity
Species Diversity
200
100
0
90ºN
100
10
60
30
0
Latitude
30ºS
60
80ºN
60
40
Latitude
Effects of Latitude
20
0
© 2004 Brooks/Cole – Thomson Learning
25
25
Species diversity
Snails
Tube worms
20
20
15
15
10
10
5
5
Coast
Deep Sea
0
Coast
Deep Sea
0
0
2,000
4,000
6,000
0
2,000
Depth (meters)
Effects of Depth
4,000
Depth (meters)
6,000
Number of diatom species
Unpolluted
stream
Polluted
stream
Number of individuals per diatom species
The Island Effect
• Isolated ecosystems studied by MacArthur
and Wilson in 1960’s
• Diversity effected by island size & degree
of isolation
• Island Biogeography theory: diversity
effected by
– Rate of species immigration to island
– Rate of extinction on island
– Equilibrium point = species diversity
© 2004 Brooks/Cole – Thomson Learning
Rate of immigration
or extinction
High
Low
Equilibrium number
Number of species on island
(a) Immigration and extinction rates
Island Biogeography
•
Immigration and Extinction Effected by
1. Size:
– small island has less immigration (small target),
– Small island has fewer resources, more extinction
2. Distance from mainland:
– Closer to mainland  more chance of immigration
•
Applied in conservation for “habitat islands”
like national parks surrounded by
development
© 2004 Brooks/Cole – Thomson Learning
Rate of immigration
or extinction
High
Low
Small island
Large island
Number of species on island
(b) Effect of island size
Number of species (percentage of sample studied)
Island Biogeography Data
• South Pacific
Islands study
looked at bird
diversity as
distance from
New Guinea
increased
NEW GUINEA
50
25
12.5
Number of amphibian and reptile
species
6.25
0 2,000 4,000 6,000 8,000 10,000
Distance from New Guinea (kilometers)
SABAMONTSERRAT
CUBA
Hispaniola
Cuba
Puerto Rico
Jamaica
100
10
Saba
Redonda
1
10
Montserrat
© 2004 Brooks/Cole – Thomson Learning
• Caribbean Island
study found
bigger islands
had more species
diversity than
smaller islands
which were
otherwise similar
100
100
1,000 10,000 100,000
Area (square miles)
Communities have different
“Types” of Species
• Native species = species that normally live
and thrive in a particular community
• Nonnative species = species that are
accidentally introduced into an area
• Keystone species = species that are more
important than their abundance or
biomass suggest
• Indicator species = species that serve as
early warnings of damage in a community
Nonnative Species
• Also called exotics, aliens, or introduced sp.
• FL examples include fire ants, hydrilla, potato
vine, peacock bass, …
– Occupy niches excluding native organisms
– Reproduce rapidly in absence of natural
predators
– Usually are very adaptable to human disturbed
environments
Common Florida Exotics
Indicator Species
• Mostly species that respond quickly to changes
in the environment
• Birds indicate tropical forest destruction
• Trout indicate pollutant presence in water
• Amphibians are a classic indicator
– Frogs case study p 170
– Frog decline and deformities
Keystone Species
• Strong interactions with other species
affect the health and survival of those
species
• They process material out of proportion to
their numbers
• Roles include: pollination, seed dispersion,
habitat modification, predation by top
carnivores, efficient recycling of animal
waste
Sea Otters
Keystone Species II
• Habitat modification
– Elephants – knock over trees in savannah to
promote grass growth & recycle nutrients
– Bats & birds – regenerate deforested areas
by depositing plant seeds in their droppings
– Beavers – create ponds forming habitats for
many pond dwelling species like fish, ducks,
& muskrats
Keystone Species III
• Top predators  exert stabilizing effect by
feeding on and regulating certain species
– Wolves, leopards, lions, gators, sharks, otters
• Over 300+ species are found on the wolf kills
made in Yellowstone
Wolves
• http://www.wolfquest.org/index.php
Waste
removal
•Dung beetles
– remove bury
and recycle
animal waste
•Establish new
plants
•Aerate soil
•Reduce
disease
causing
microorganis
ms
Species Interactions
• Interactions may be harmful, beneficial, or
have no effect at all
• Competition: Intraspecific or Interspecific
• Predation, Mutualism (Symbiosis),
Commensalism, Parasitism
Intraspecific Competition
• Competition between members of the same
species for a common resource
• Resource: food, space, mates, etc.
• Territoriality
– Organisms patrol or mark an area
– Defend it against others
– Good territories have
• Abundant food, good nesting sites, low predator pop.
– Disadvantage = Energy, Reduce gene pool
Territoriality Examples
Interspecific Competition
•
•
•
•
•
2 or more different species involved
Competing for food, space, sunlight, water,
space, nesting sites or other limited resource
If resources abundant, they can be shared but in
nature they are always limited
If fundamental niches overlap  competition
One of the species must…
1.
2.
3.
4.
Migrate if possible
Shift feeding habits or behavior = Evolve
Suffer a sharp population decline
Become extinct
Connell’s
Barnacles
Methods of competition
1. Interference
•
•
One species limits access of others to a
resource, regardless of its abundance
Hummingbird territoriality, Desert plant
allelopathy
2. Exploitation
•
•
Species have equal resource access, differ
in speed of use
Quicker species = more of it & hampers
growth, reproduction and survival of other
species
Allelopathy
Competitive Exclusion Principle
• One species eliminates another in an area
through competition for limited resources
– Two Paramecium species
– Identical conditions grown apart both do well
– Grown together one eliminates the other
• The niches of two species cannot overlap
significantly for a long period of time
High
Relative population density
Paramecium
aurelia
Paramecium
caudatum
Low
0
2
4
6
8
10
12
Days
Each species grown alone
14
16
18
High
Relative population density
Paramecium
aurelia
Paramecium
caudatum
Low
0
2
4
6
8
10
12
Days
Both species grown together
14
16
18
Avoiding Competition
• Resource partitioning = dividing of scarce
resources to species at different
– Times
– Methods of use
– Different locations
• Species occupy realized niche, a small
fraction of their fundamental niches
– Lions vs leopards, hawks vs. owls
Number of individuals
© 2004 Brooks/Cole – Thomson Learning
Species 1
Species 2
Region
of
niche overlap
Number of individuals
Resource use
Species 1
Species 2
Resource use
Predation
• Members of one species feed directly on all
or part of a living organism of a different
species
• Individuals  predator benefits, prey harmed
• Population  prey benefits: take out the
weak, greater resource access, improved
gene pool
• Predator plays important ecological role
Predation
Predation strategies
1. Herbivores – sessile prey, no need to
hurry
2. Pursuit – speed (cheetah), eyesight
(eagles), cooperation (wolves)
3. Ambush – camouflage for hiding (praying
mantis), lures (anglerfish)
Ambush Predators
Prey defenses
• Camouflage – change color, blend with
environment,
• Chemical warfare – produce chemicals which
are poisonous, irritating, bad smelling or
tasting
• Warning coloration – bright colors advertise
inedibility (mimics take advantage of this)
• Behavioral strategies – Puffing up, mimicking
predators, playing dead, schooling
Warning coloration
Batesian mimicry
Mullerian mimicry
Span worm
Wandering leaf insect
Poison dart frog
Viceroy butterfly mimics
monarch butterfly
Bombardier beetle
Hind wings of io moth
resemble eyes of a
much larger animal
Foul-tasting monarch
butterfly
When touched, the
snake caterpillar
changes shape to look
like the head of a snake
Parasitism
•
•
•
One species feeds on part of another
organism (the host) without killing it
Specialized form of predation
Parasite Characteristics
1.
2.
3.
4.
•
Usually smaller than the host
Closely associated with host
Draws nourishment from & slowly weakens host
Rarely kills the host
Examples = Tapeworms, ticks, fleas, fungi
Parasites
Malaria
According to the World Health
Organization there are 300 to 500
million clinical cases of malaria
each year resulting in 1.5 to 2.7
million deaths
The disease kills more than one
million children - 2,800 per day each year in Africa alone. In
regions of intense transmission,
40% of toddlers may die of acute
malaria.
In the early 1960s, only 10% the
world's population was at risk of
contracting malaria. This rose to
40% as mosquitoes developed
resistance to pesticides and
malaria parasites developed
resistance to treatment drugs.
Malaria is now spreading to areas
previously free of the disease.
Mutualism
• Symbiotic relationship where both species
benefit
• Pollination, Nutrition, Protection are main
benefits
• Not really cooperation, both benefit by
exploiting the other
Mutualism II
Examples
1. Lichens – fungi & algae living together
 food for one, structure for the other
2. Plants and Rhizobium bacteria  one
gets sugars the other gets nitrogen
3. Oxpeckers and Rhinos  food for one,
less parasites for the other
4. Protists and termites  break down
wood for one, nutrients for the other
Oxpeckers and black rhinoceros
Clown fish and sea anemone
Human Intestinal Symbionts
•
One species benefits
the other is neither
harmed nor helped
– Examples
1. Herbs growing in the
shade of trees
2. Birds building nests in
trees
3. Epiphytes = “Air plants”
which attach
themselves to the trunk
or branches of trees
-they have a solid base to
grow on and better
access to sunlight & rain
Commensalism
What interaction is this?
What interaction is this?
What interaction is this?