Download II. A. Ecosystem Structure

II. Living World
A. Ecosystem Structure
Biological populations & communities
Ecological niches/Keystone Species
Interactions among species
Species diversity
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Biological Populations &
Communities
Biology Review!!
• What is the basic unit of life?
THE CELL
What do biologists study?
• Organization of biology
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Cell
Tissues
Organs
Organ Systems
Organism
What do ecologists study?
• Ecologists Study Connections in Nature
• Levels of organization
• Species/Population
• Community
Definitions coming up in 2 slides
• Ecosystem
• Biosphere
Species Make Up the Encyclopedia of Life
• 1.75 Million species identified
• Insects make up most of the known species
• Perhaps 10–14 million species not yet identified
Biosphere
Parts of the earth's air, water, and soil
where life is found
Ecosystem
A community of different species
interacting with one another and with their
nonliving environment of matter and energy
Community
Populations of different species living in a particular
place, and potentially interacting with each other
Population
Organism
Cell
Molecule
Atom
A group of individuals of the same species living
in a particular place
An individual living being
The fundamental structural and functional unit
of life
Chemical combination of two or more atoms of the
same or different elements
Smallest unit of a chemical element that exhibits
its chemical properties
Stepped Art
Fig. 3-3, p. 52
Population of Glassfish in the Red Sea
Ecological Niches
• 4-6 What Roles Do Species Play in Ecosystems?
• Concept 4-6A Each species plays a specific ecological role called
its niche.
• Concept 4-6B Any given species may play one or more of five
important roles—native, nonnative, indicator, keystone, or
foundation roles—in a particular ecosystem.
Each Species Plays a Unique
Role in Its Ecosystem
• Ecological niche, niche
• Pattern of living
• Generalist species
• Broad niche: can live in many places, eat many things, tolerate
many conditions
• Specialist species
• Narrow niche: live only in one type of habitat OR only eat a few
types of food OR tolerate a narrow range of conditions
• Specialists are more prone to extinction!
Specialized Feeding Niches of
Various Bird Species in a
Coastal Wetland
Specialist Species and
Generalist Species Niches
Which is better?
Generalist vs. Specialist
• Cockroaches
• Generalists
• High reproductive rates
• Giant panda and tiger salamanders
• Specialists
• Low reproductive rates
• Is it better to be a generalists or specialist?
• It depends on the conditions… if constant (like the rainforest)
specialists have an easier time b/c of less competition. If
conditions change, generalists can adapt better.
Cockroach: Nature’s Ultimate
Survivor
• 350 mya… now over 3,500 species
• Can eat algae, dead bugs, fingernail clippings, salt in tennis
shoes, paper…
• Survive:
• 1 mo. without food, radiation, 48 hours frozen
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Highly sophisticated senses (antenae, eyes)
Highly reproductive (1 roach = 10 million in one year)
Can detect poisons
Carry viruses & bacteria
Cockroach
Niches Can Be Occupied by
Native and Nonnative Species
• Native species – those that normally live & thrive in a
particular ecosystem
• Nonnative species (invasive, alien, exotic) – migrate or are
accidentally or deliberately introduced into an ecosystem
• May spread rapidly (lack predators, disease), displacing natives
• Not all are villains
• Food (crops, cattle)
Kudzu
• Brought to the US from Japan.
•Between 1935 & 1950
farmers were encouraged to
plant it to reduce erosion
(dust bowl).
•It crowds out native species,
smothering & killing them.
Abandoned house
Zebra Mussel
• Accidentally transported into US
waters by ballast in ships (1988)
• Have made a strong hold in the
great lakes
• Economic issue: ruins boat motors,
sewage lines… anything it touches
• Ecological issue: outcompetes
natives
The Famous Photo
• When species are released
accidentally or deliberately, they
may not have natural predators, or
may outcompete the natives
• If this occurs, the ecosystem can be
forever changed
Indicator Species Serve as
Biological Smoke Alarms
• Indicator species
• Can monitor environmental quality
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Trout – DO & Temp. indicator
Birds – habitat loss, pesticides
Butterflies – indicate plant issues
Frogs …
Life Cycle of a Frog
•An amphibians development makes it
vulnerable to different environmental conditions
as it grows.
•Early development: water
•Later: land
•Food: insects (pesticide)
•Skin: semi-permeable
•Eggs: no shells
Case Study: Why Are Amphibians
Vanishing?
• Habitat loss and fragmentation
• Prolonged drought
• Pollution
• Increase in UV radiation
• Parasites
• Viral and fungal diseases
• Climate change
• Overhunting
• Nonnative predators and competitors
Case Study: Why Are Amphibians
Vanishing? … Why should we care?
• Importance of amphibians
• Sensitive biological indicators of environmental changes
• Adult amphibians
• Important ecological roles in biological communities
• Genetic storehouse of pharmaceutical products waiting to be
discovered
Keystone, Foundation Species
Determine Structure, Function of
Their Ecosystems
• Keystone species – have a large effect on types and
abundance of other species in their ecosystem
– Pollinators
– Top predator
• Foundation species - Create or enhance their habitats, which
benefit others (sometimes… APES exam… listed as keystone)
• Elephants
• Beavers
• Foundation = HABITAT
• Keystone …MORE important = FUNCTION
Case Study: Why Should We
Protect Sharks?
• Keystone species
– Eat dead and dying fish in the ocean
– Strong immune systems
• Wounds do not get infected
• Almost never get cancer
• Could help humans if we understood their immune system
• Sharks killed because of
– Fear
– Use of liver, meat, hides, fins
– Overfished due to slow reproduction
• Sharks have been around 400 million years
Interactions among Species
• 5-1 How Do Species Interact?
• Concept 5-1 Five types of species interactions—competition,
predation, parasitism, mutualism, and commensalism—affect the
resource use and population sizes of the species in an ecosystem.
• 5-2 How Can Natural Selection Reduce Competition between
Species?
• Concept 5-2 Some species develop adaptations that allow them
to reduce or avoid competition with other species for resources.
Species Interact in Five Major
Ways
• Interspecific Competition
• Competition between 2 different species
• Intraspecific Competition: same species
• Predation
• Predator feeds on Prey
• Parasitism
• Parasite feeds on the body (or energy) of the host usually while living in
or on the host
• Mutualism
• Both species benefit
• Commensalism
• One species benefits, the other is not affected
Most Species Compete with
One Another for Certain
Resources
• Competition
• Occurs when there is overlap in
resource use
• Competitive Exclusion
(Gause’s) Principle
• No two species can occupy
exactly the same niche for very
long
Some Species Evolve Ways to
Share Resources
• Resource partitioning
• Reduce niche overlap
• Use shared resources at different
• Times
• Places
• Ways
Competing Species Can Evolve
to Reduce Niche Overlap
Sharing the Wealth: Resource
Partitioning
Specialist Species of
Honeycreepers
Most Consumer Species Feed
on Live Organisms of Other
Species (1)
• Predators may capture prey by
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Walking
Swimming
Flying
Pursuit and ambush
Camouflage
Chemical warfare
Most Consumer Species Feed
on Live Organisms of Other
Species (2)
• Prey may avoid capture by
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Camouflage
Chemical warfare
Warning coloration
Mimicry
Deceptive looks
Deceptive behavior
Some Ways Prey Species Avoid
Their Predators
Importance of Predators
• Role in natural selection
• Keystone Species
• Keep populations of prey in
balance
Video: Otter feeding
Predator and Prey Species Can
Drive Each Other’s Evolution
• Intense natural selection pressures between predator and prey
populations
• Coevolution
• Bats & moths
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Bats hunt w/ echolocation
Moths evolve to pick up frequencies and drop
Bats evolve different frequencies
Moths evolve jamming frequency clicks
Bats evolve to stop echolocating and listen for clicks
Coevolution: A
Langohrfledermaus
Bat Hunting a Moth
Some Species Feed off Other
Species by Living on or in
Them
• Parasitism
• Live in: tapeworm
• Live on: fleas
• Little contact: cowbird
• Parasite-host interaction may lead to co-evolution
• Malaria and sticky protein to avoid spleen
Parasitism: Tree with Parasitic
Mistletoe, Trout with BloodSucking Sea Lampreys
Mistletoe
Sea lampreys
In Some Interactions, Both
Species Benefit
• Mutualism
• Nutrition and protection relationship
• Gut inhabitant mutualism
Mutualism: Oxpeckers Clean
Rhinoceros; Anemones Protect
and Feed Clownfish
In Some Interactions, One
Species Benefits and the Other
Is Not Harmed
• Commensalism
• Epiphytes
• Birds nesting in trees
Commensalism: Bromeliad
Roots on Tree Trunk Without
Harming Tree
The American Alligator
Core Case Study: Why Should We Care
about the American Alligator?
• Largest reptile in North America
• 1930s: Hunters and poachers
• Importance of gator holes and nesting mounds
• 1967: endangered species
• 1977: comeback, threatened species
Southern Sea Otter
Core Case Study: Southern Sea Otters:
Are They Back from the Brink of
Extinction?
• Habitat
• Hunted: early 1900s
• Partial/Slow recovery
• Why care about sea otters?
– Ethics
– Keystone species
– Tourism dollars
Species Diversity & Edge
Effects
• 4-5 What Is Species Diversity and Why Is It Important?
• Concept 4-5 Species diversity is a major component of
biodiversity and tends to increase the sustainability of ecosystems.
Species Diversity: Variety,
Abundance of Species in a Particular
Place
• Species diversity
• Species richness: number of different species
• Species evenness: relative abundance of each of those
species
• Diversity varies with geographical location
• Most species-rich communities are in the tropics
• Tropical rain forests, Coral reefs
• Diversity decreases as you move toward poles
Variations in Species Richness and
Species Evenness
Species-Rich Ecosystems Tend to
Be Productive and Sustainable
• Species Richness increases an ecosystem’s:
• Plant productivity
• Sustainability
• This means it will withstand disturbances better
Science Focus: Species
Richness on Islands
• Species equilibrium model, theory of island biogeography
• Species richness depends on:
• Immigration
• Extinction
• To reach equilibrium for species richness, ideally they are equal.
Science Focus: Species
Richness on Islands
• What determines an islands immigration & extinction rates:
• Island size
• Bigger = better
• Large target for immigration
• More resources for avoiding extinction
• Distance from the mainland
• Closer = better
• Easier (more) immigration
• Useful in thinking about “habitat islands”
Animation: Speciation on an
archipelago
END OF LECTURE II Part A
III. Population
A. Population
Biology Concepts
Population ecology
Carrying capacity (limiting factors, range of tolerance)
Reproductive strategies
Survivorship
Population Dynamics
5-3 What Limits the Growth of
Populations?
• Concept 5-3 No population can continue to grow indefinitely
because of limitations on resources and because of
competition among species for those resources.
Populations Have Certain
Characteristics (1)
• Populations differ in
• Distribution
• Numbers
• Age structure
• Population dynamics
Populations Have Certain
Characteristics (2)
• Changes in population characteristics due to:
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Temperature
Presence of disease organisms or harmful chemicals
Resource availability
Arrival or disappearance of competing species
Most Populations Live Together in
Clumps or Patches (1)
• Population distribution
• Clumping
• Uniform dispersion
• Random dispersion
Most Populations Live Together in
Clumps or Patches (2)
• Why clumping?
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Species tend to cluster where resources are available
Groups have a better chance of finding clumped resources
Protection from predators
Packs allow some to get prey
Temporary groups for mating and caring for young
Populations Can Grow, Shrink, or
Remain Stable (1)
• Population size governed by
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Births
Deaths
Immigration
Emigration
• Population change =
(births + immigration) – (deaths + emigration)
Populations Can Grow, Shrink, or
Remain Stable (2)
• Age structure
• Pre-reproductive age
• Reproductive age
• Post-reproductive age
No Population Can Grow
Indefinitely:
J-Curves and S-Curves (1)
• Biotic potential
• Low
• High
• Intrinsic rate of increase (r)
• Individuals in populations with high r
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Reproduce early in life
Have short generation times
Can reproduce many times
Have many offspring each time they reproduce
No Population Can Grow
Indefinitely:
J-Curves and S-Curves (2)
• Size of populations limited by
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Light
Water
Space
Nutrients
Exposure to too many competitors, predators or infectious
diseases
No Population Can Grow
Indefinitely:
J-Curves and S-Curves (3)
• Environmental resistance
• Carrying capacity (K)
• Exponential growth
• Logistic growth
Carrying Capacity
• The maximum number of individuals that can be supported by
an ecosystem indefinately.
No Population Can Continue to
Increase in Size Indefinitely
Abiotic Factors Can Limit Population
Growth
• Range of Tolerance
• The range of chemical or physical conditions that
must be maintained for a population to stay alive,
grow, develop & function normally
Range of Tolerance for a
Population of Organisms
INSERT FIGURE 3-10 HERE
Abiotic Factors Can Limit Population
Growth
• Limiting Factor
• A single factor that limits the growth, abundance,
or distribution of a population in an ecosystem
• Limiting factor principle
• Too much or too little of any abiotic factor can limit
or prevent growth of a population, even if all other
factors are at or near the optimal range of
tolerance
Logistic Growth of a Sheep
Population on the island of
Tasmania, 1800–1925
When a Population Exceeds Its
Habitat’s Carrying Capacity, Its
Population Can Crash
• Carrying capacity: not fixed
• Reproductive time lag may lead to overshoot
• Dieback (crash)
• Damage may reduce area’s carrying capacity
Exponential Growth,
Overshoot, and Population
Crash of a Reindeer
Under Some Circumstances
Population Density Affects
Population Size
• Density-independent population control
• Weather events
• Natural disasters
• Density-dependent population controls
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Predation
Parasitism
Infectious disease
Competition for resources
Several Different Types of
Population Change Occur in
Nature
• Stable
• Irruptive
• Cyclic fluctuations, boom-and-bust cycles
• Top-down population regulation
• Bottom-up population regulation
• Irregular
Population Cycles for the
Snowshoe Hare and Canada
Lynx
Humans Are Not Exempt from
Nature’s Population Controls
• Ireland
• Potato crop in 1845
• Bubonic plague
• Fourteenth century
• AIDS
• Global epidemic
Case Study: Exploding WhiteTailed Deer Population in the
U.S.
• 1900: deer habitat destruction and uncontrolled hunting
• 1920s–1930s: laws to protect the deer
• Current population explosion for deer
• Lyme disease
• Deer-vehicle accidents
• Eating garden plants and shrubs
• Ways to control the deer population
Reproductive Strategies
• Species Have Different Reproductive
Patterns
• r-Selected species, opportunists
• K-selected species, competitors
Positions of r- and K-Selected
Species on the S-Shaped
Population Growth Curve
Survivorship
Animation: Life history
patterns