Transcript Population

MILLER/SPOOLMAN
LIVING IN THE ENVIRONMENT
17TH
Chapter 5
Biodiversity, Species
Interactions, and Population
Control
Core Case Study: Southern Sea Otters: Are
They Back from the Brink of Extinction?
• Habitat: Western coast of US
• Hunted: early 1900s to near extinction
• Partial recovery
• Why care about sea otters?
• Ethics
• Tourism dollars
• Keystone species: Without them, sea urchins and other kelp
eating species would destroy the kelp forests and biodiversity
associated with it.
Southern Sea Otter
Fig. 5-1a, p. 104
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.
Species Interact in Five Major Ways
• Interspecific Competition-occurs when members of two or
more species interact to gain access to the same resource
• Predation
• Parasitism
• Mutualism
• Commensalism
Most Species Compete with One
Another for Certain Resources
• For limited resources—food, water, light, space
• Ecological niche for exploiting resources: remember
that generalists with a broad niche and specialists
have a narrow niche.
• Some niches overlap: intensifying the competition
between the species, forcing adaptations and/or
natural selection.
Some Species Evolve Ways to Share
Resources
• Resource partitioning: allows for sharing of
resources and reduces competition for resources
• Using only parts of resource
• Using at different times
• Using in different ways
Resource Partitioning Among Warblers
Fig. 5-2, p. 106
Specialist Species of Honeycreepers
Fig. 5-3, p. 107
Most Consumer Species Feed on Live
Organisms of Other Species (1)
• Predators may capture prey by
1. Walking
2. Swimming
3. Flying
4. Pursuit and ambush
5. Camouflage
6. Chemical warfare
Predator-Prey Relationships
Fig. 5-4, p. 107
Most Consumer Species Feed on Live
Organisms of Other Species (2)
• 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
(a) Span worm
Fig. 5-5a, p. 109
(b) Wandering leaf insect
Fig. 5-5b, p. 109
(c) Bombardier beetle
Fig. 5-5c, p. 109
(d) Foul-tasting monarch butterfly
Fig. 5-5d, p. 109
(e) Poison dart frog
Fig. 5-5e, p. 109
(f) Viceroy butterfly mimics monarch
butterfly
Fig. 5-5f, p. 109
(g) Hind wings of Io moth resemble
eyes of a much larger animal.
Fig. 5-5g, p. 109
(h) When touched, snake
caterpillar changes shape to look
like head of snake.
Fig. 5-5h, p. 109
Science Focus: Threats to Kelp Forests
• Kelp forests: biologically diverse marine habitat
• Major threats to kelp forests
1. Sea urchins
2. Pollution from water run-off
3. Global warming
Purple Sea Urchin
Fig. 5-A, p. 108
Predator and Prey Interactions Can
Drive Each Other’s Evolution
• 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
Coevolution: A Langohrfledermaus
Bat Hunting a Moth
Fig. 5-6, p. 110
Some Species Feed off Other Species
by Living on or in Them
• Parasitism
• Parasite is usually much smaller than the host
• Parasite rarely kills the host. (Why is this
important?)
• Parasite-host interaction may lead to coevolution
Parasitism: Trout with Blood-Sucking Sea Lamprey
Fig. 5-7, p. 110
Video
• Evolution: Ancient Farmers of the Amazon
• http://www.youtube.com/watch?v=dOV0E5FaKoQ
In Some Interactions, Both Species
Benefit
• Mutualism
• Nutrition and protection relationship
• Gut inhabitant mutualism
• Not cooperation: it’s mutual exploitation—
unintentional cooperation. Each species is working
towards their own selfish survival!
Mutualism: Hummingbird and Flower
Fig. 5-8, p. 110
Mutualism: Oxpeckers Clean Rhinoceros; Anemones
Protect and Feed Clownfish
Fig. 5-9, p. 111
(a) Oxpeckers and black rhinoceros
Fig. 5-9a, p. 111
(b) Clownfish and sea anemone
Fig. 5-9b, p. 111
In Some Interactions, One Species Benefits
and the Other Is Not Harmed
• Commensalism
• Epiphytes
• Birds nesting in trees
Commensalism: Bromiliad Roots on Tree Trunk Without
Harming Tree
Fig. 5-10, p. 111
5-2 What Limits the Growth of
Populations?
• Concept 5-2 No population can continue to grow
indefinitely because of limitations on resources and
because of competition among species for those
resources.
Most Populations Live Together in
Clumps or Patches (1)
• Population: group of interbreeding individuals of the
same species
• Population distribution
1. Clumping
2. Uniform dispersion
3. Random dispersion
Most Populations Live Together in
Clumps or Patches (2)
• Why clumping?
1. Species tend to cluster where resources are
available
2. Groups have a better chance of finding clumped
resources
3. Protects some animals from predators
4. Packs allow some to get prey
Population of Snow Geese
Fig. 5-11, p. 112
Generalized Dispersion Patterns
Fig. 5-12, p. 112
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—the distribution of individuals among
various age groups
• Pre-reproductive age
• Reproductive age
• Post-reproductive age
• A population with a large number in the
reproductive years will increase in size
• A population with a large number in post
reproductive years will decrease.
Some Factors Can Limit Population
Size
• Range of tolerance
• Variations in physical and chemical environment
• 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
Trout Tolerance of Temperature
Fig. 5-13, p. 113
No Population Can Grow Indefinitely:
J-Curves and S-Curves (1)
• Size of populations controlled by limiting factors:
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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 (2)
• Environmental resistance
• The combination of all factors acting to limit the
growth of a population
• Carrying capacity (K)
• Maximum population a given habitat can sustain
No Population Can Grow Indefinitely:
J-Curves and S-Curves (3)
• 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
Logistic Growth of Sheep in Tasmania
Fig. 5-15, p. 115
Science Focus: Why Do California’s Sea
Otters Face an Uncertain Future?
• Low biotic potential
• Prey for orcas
• Cat parasites—HOW DID THAT get in the ocean?!
• Thorny-headed worms
• Toxic algae blooms—triggered by urea (ingredient in fertilizer)
• PCBs and other toxins—present in their food source thanks to human
activities/pollution!
• Oil spills
• Why are sea otters considered an INDICATOR SPECIES?
Population Size of Southern Sea Otters Off the Coast of
So. California (U.S.)
Fig. 5-B, p. 114
Case Study: Exploding White-Tailed
Deer Population in the U.S.
• 1900: deer habitat destruction and uncontrolled hunting
reduced the population to 500,000
• 1920s–1930s: laws to protect the deer
• Current population explosion for deer (Today there are 25
million)
• Spread Lyme disease (carried by ticks)
• Deer-vehicle accidents (1.5 million a year!)
• Eating garden plants and shrubs
• Ways to control the deer population
• Did you read about the birth control options???!!!!!
Mature Male White-Tailed Deer
Fig. 5-16, p. 115
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
• Population crash
• Damage may reduce area’s carrying capacity
Exponential Growth, Overshoot, and
Population Crash of a Reindeer
Fig. 5-17, p. 116
Species Have Different Reproductive
Patterns (1)
• Some species
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Many, usually small, offspring
Little or no parental care
Massive deaths of offspring
Insects, bacteria, algae
Species Have Different Reproductive
Patterns (2)
• Other species
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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
Under Some Circumstances Population
Density Affects Population Size
• 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
• Population surge, followed by crash
• Cyclic fluctuations, boom-and-bust cycles
• Top-down population regulation
• Bottom-up population regulation
• Irregular
Population Cycles for the Snowshoe Hare and
Canada Lynx
Fig. 5-18, p. 118
Humans Are Not Exempt from
Nature’s Population Controls
• Ireland
• Potato crop in 1845—crop was infected with a fungus that
destroyed the crop---the lack of food killed ONE MILLION
people—3 million emigrated!
• Bubonic plague
• Fourteenth century—killed 25 MILLION people
• The baceria cause normally lives in rodents, but was
transferred to humans by FLEAS!
• Spread was due to sanitation issues
• AIDS
• Global epidemic—in the past 30 years…it has killed 27
MILLION people! Averages 4 deaths/minute
5-3 How Do Communities and Ecosystems
Respond to Changing Environmental
Conditions?
• Concept 5-3 The structure and species composition
of communities and ecosystems change in response
to changing environmental conditions through a
process called ecological succession.
Communities and Ecosystems Change over
Time: Ecological Succession
• Natural ecological restoration
• Primary succession
• Secondary succession
Some Ecosystems Start from Scratch:
Primary 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
Primary Ecological Succession
Fig. 5-19, p. 119
Some Ecosystems Do Not Have to Start from
Scratch: Secondary Succession (1)
• Some soil remains in a terrestrial system
• Some bottom sediment remains in an aquatic system
• Ecosystem has been
• Disturbed
• Removed
• Destroyed
Natural Ecological Restoration of Disturbed Land
Fig. 5-20, p. 120
Secondary Ecological Succession in Yellowstone Following
the 1998 Fire
Fig. 5-21, p. 120
Some Ecosystems Do Not Have to Start from
Scratch: Secondary Succession (2)
• 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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Fires
Hurricanes
Clear-cutting of forests
Plowing of grasslands
Invasion by nonnative species
Living Systems Are Sustained through
Constant Change
• Inertia, persistence
• Ability of a living system to survive moderate
disturbances
• Resilience
• Ability of a living system to be restored through
secondary succession after a moderate disturbance
• Some systems have one property, but not the other:
tropical rainforests