Download 1 Southern Sea Otters: Are They Back from the Brink (邊緣) of

Endangered species: Southern Sea Otter
Beetle
Southern Sea Otters: Are They Back from the
Brink (邊緣) of Extinction?
Species Interact in Five Major Ways
• Habitat
• Interspecific competition
• Hunted: early 1900s
• Predation
• Partial recovery • Why care about sea otters?
• Ethics
• Tourism dollars
• Keystone species
Most Species Compete with One Another for Certain Resources
• For limited resources
• Parasitism
• Mutualism
• Commensalism
Some Species Evolve Ways to Share Resources
• Resource partitioning
• Using only parts of resource
• Ecological niche for exploiting resources
• Using at different times
• Some niches overlap
• Using in different ways
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Resource Partitioning Among Warblers (鶯)
Blackburnian
Warbler
Black-throated
Green Warbler
Cape May
Warbler
Bay-breasted
Warbler
Predator‐Prey Relationships
Specialist Species of Honeycreepers Yellow-rumped
Warbler
Most Consumer Species Feed on Live Organisms of Other Species
• Prey may avoid capture by
1. Run, swim, fly
2. Protection: shells, bark, thorns
3. Camouflage
4. Chemical warfare
5. Warning coloration
6. Mimicry
7. Deceptive looks
8. Deceptive behavior
camouflage
camouflage
(a) Span worm
(b) Wandering leaf insect
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warning coloration
chemical warfare
(d) Foul-tasting monarch butterfly
(c) Bombardier beetle
mimicry
warning coloration
(e) Poison dart frog
(g) Hind wings of Io moth resemble
eyes of a much larger animal.
(f) Viceroy (總督) butterfly mimics monarch
butterfly
(h) When touched, snake
caterpillar changes shape to look
like head of snake.
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Threats to Kelp Forests
Purple Sea Urchin
• Kelp forests: biologically diverse marine habitat
• Major threats to kelp forests
1. Sea urchins
2. Pollution from water run‐off
3. Global warming
Predator and Prey Interactions Can Drive Each Other’s Evolution
Coevolution: A Langohrfledermaus Bat (長耳蝠) Hunting a Moth
• Intense natural selection pressures between predator and prey populations
• Coevolution
• Interact over a long period of time
• Bats and moths: echolocation of bats and sensitive hearing of moths
Some Species Feed off Other Species by Living on or in Them
Parasitism: Trout with Blood‐Sucking Sea Lamprey (七鰓鰻；
八目鰻)
• Parasitism • Parasite is usually much smaller than the host
• Parasite rarely kills the host
• Parasite‐host interaction may lead to coevolution
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Mutualism: Hummingbird and Flower In Some Interactions, One Species Benefits and the Other Is Not Harmed
Mutualism: Oxpeckers (牛椋鳥) Clean Rhinoceros; Anemones Protect and Feed Clownfish Commensalism: Bromeliad (鳳梨科植物) Roots on Tree Trunk Without Harming Tree
• Commensalism • Epiphytes (附生植物)
• Birds nesting in trees
Most Populations Live Together in Clumps or Patches
Population of Snow Geese
• Population: group of interbreeding individuals of the same species
• Population distribution 1. Clumping
2. Uniform dispersion
3. Random dispersion
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Generalized Dispersion Patterns
Populations Can Grow, Shrink, or Remain Stable
• Population size governed by
•
•
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•
Births
Deaths
Immigration
Emigration
• Population change =
(births + immigration) – (deaths + emigration)
Trout Tolerance of Temperature
Some Factors Can Limit Population Size
• Range of tolerance
Lower limit
of tolerance
No
organisms
Few
organisms
Higher limit
of tolerance
Abundance of organisms
Few
organisms
No
organisms
• Limiting factor principle
• Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance
• Precipitation
• Nutrients • Sunlight, etc
No Population Can Grow Indefinitely: J‐Curves and S‐Curves
• Size of populations controlled by limiting factors:
•
•
•
•
•
Light
Water
Space
Nutrients
Exposure to too many competitors, predators or infectious diseases
Population size
• Variations in physical and chemical environment
Zone of
Zone of
intolerance physiological
stress
Low
Optimum range
Zone of
Zone of
physiological intolerance
stress
Temperature
High
No Population Can Grow Indefinitely: J‐Curves and S‐Curves
• Environmental resistance • All factors that act to limit the growth of a population
• Carrying capacity (K)
• Maximum population a given habitat can sustain
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No Population Can Grow Indefinitely: J‐Curves and S‐Curves
Logistic Growth of Sheep in Tasmania
• Exponential growth
• Starts slowly, then accelerates to carrying capacity when meets environmental resistance
• Logistic growth
• Decreased population growth rate as population size reaches carrying capacity
Why Do California’s Sea Otters Face an
Uncertain Future?
Population Size of Southern Sea Otters Off the Coast of S. California (U.S.)
• Low biotic potential
• Prey for orcas
• Cat parasites
• Thorny‐headed worms
• Toxic algae blooms
• PCBs and other toxins
• Oil spills
Exploding White-Tailed Deer Population in
the U.S.
Mature Male White‐Tailed Deer
• 1900: deer habitat destruction and uncontrolled hunting
• 1920s–1930s: laws to protect the deer
• Current population explosion for deer
• Spread Lyme disease
• Deer‐vehicle accidents
• Eating garden plants and shrubs
• Ways to control the deer population
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When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash
• A population exceeds the area’s carrying capacity
• Reproductive time lag may lead to overshoot (高過頭)
• Population crash
• Damage may reduce area’s carrying capacity
Exponential Growth, Overshoot, and Population Crash of a Reindeer
Species Have Different Reproductive Patterns (1)
• Some species
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•
•
•
Species Have Different Reproductive Patterns
• Other species
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•
•
•
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Reproduce later in life
Small number of offspring with long life spans
Young offspring grow inside mother
Long time to maturity
Protected by parents, and potentially groups
Humans
Elephants Many, usually small, offspring
Little or no parental care
Massive deaths of offspring
Insects, bacteria, algae
Under Some Circumstances Population Density Affects Population Size
• Density‐dependent population controls
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Predation
Parasitism
Infectious disease
Competition for resources
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Population Cycles for the Snowshoe Hare and Canada Lynx
Several Different Types of Population Change Occur in Nature
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• Irruptive
• Population surge, followed by crash
• Cyclic fluctuations, boom‐and‐bust cycles
• Top‐down population regulation
• Bottom‐up population regulation • Irregular Population size (thousands)
• Stable
Hare
Lynx
140
120
100
80
60
40
20
0
1845
1855
1865
1875
1885
1895
1905
1915
1925
1935
Year
Humans Are Not Exempt from Nature’s Population Controls
• Ireland
• The Irish Potato Famine in 1845
Communities and Ecosystems Change over Time: Ecological Succession
• Natural ecological restoration
• Primary succession
• Secondary succession
• Bubonic plague
• Fourteenth century
• AIDS
• Global epidemic
Some Ecosystems Start from Scratch (裂隙) : Primary Succession
Primary Ecological Succession
• No soil in a terrestrial system
• No bottom sediment in an aquatic system
• Takes hundreds to thousands of years
• Need to build up soils/sediments to provide necessary nutrients
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Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession
Natural Ecological Restoration of Disturbed Land
• Some soil remains in a terrestrial system
• Some bottom sediment remains in an aquatic system
• Ecosystem has been
• Disturbed
• Removed
• Destroyed
Secondary Ecological Succession in Yellowstone Following the 1998 Fire
Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession
• Primary and secondary succession
• Tend to increase biodiversity
• Increase species richness and interactions among species
• Primary and secondary succession can be interrupted by
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Succession Doesn’t Follow a Predictable Path
Fires
Hurricanes
Clear‐cutting of forests
Plowing of grasslands
Invasion by nonnative species
Three Big Ideas
• Traditional view • Balance of nature and a climax community
1. Certain interactions among species affect their use of resources and their population sizes.
• Current view 2. There are always limits to population growth in nature.
• Ever‐changing mosaic of patches of vegetation
• Mature late‐successional ecosystems • State of continual disturbance and change
3. Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession).
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