Biodiversity, Species Interactions, and Population Control...
Transcript of Biodiversity, Species Interactions, and Population Control...
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Biodiversity, Species Interactions,
and Population Control
Chapter 5
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Core Case Study: Southern Sea Otters: Are
They Back from the Brink of Extinction?
Habitat
Hunted: early 1900s
Partial recovery
Why care about sea otters?
• Ethics
• Keystone species
• Tourism dollars
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Southern Sea Otter
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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.
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Most Consumer Species Feed on Live
Organisms of Other Species (1)
Predators may capture prey by
• Walking
• Swimming
• Flying
• Pursuit and ambush
• Camouflage
• Chemical warfare
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Most Consumer Species Feed on Live
Organisms of Other Species (2)
Prey may avoid capture by
• Camouflage
• Chemical warfare
• Warning coloration
• Mimicry
• Deceptive looks
• Deceptive behavior
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Fig. 5-2, p. 103
(h) When touched,
snake caterpillar changes
shape to look like head of snake.
(a) Span worm (b) Wandering leaf insect
(c) Bombardier beetle (d) Foul-tasting monarch butterfly
(f) Viceroy butterfly mimics
monarch butterfly(e) Poison dart frog
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
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Predator and Prey Species Can Drive
Each Other’s Evolution
Intense natural selection pressures between
predator and prey populations
Coevolution
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Coevolution: A Langohrfledermaus
Bat Hunting a Moth
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Some Species Feed off Other Species by
Living on or in Them
Parasitism
Parasite-host interaction may lead to coevolution
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Parasitism: Tree with Parasitic Mistletoe,
Trout with Blood-Sucking Sea Lampreys
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In Some Interactions, Both Species
Benefit
Mutualism
Nutrition and protection relationship
Gut inhabitant mutualism
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Mutualism: Oxpeckers Clean Rhinoceros;
Anemones Protect and Feed Clownfish
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Fig. 5-5a, p. 106(a) Oxpeckers and black rhinoceros
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Fig. 5-5b, p. 106(b) Clownfish and sea anemone
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In Some Interactions, One Species
Benefits and the Other Is Not Harmed
Commensalism
Epiphytes
Birds nesting in trees
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Commensalism: Bromiliad Roots on Tree
Trunk Without Harming Tree
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Species Interactions
Or, An analogy for high school
relationships.
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Basic types of Species interaction
Predation
Parasitism
Mutualism
Commensalism
Interspecific Competition
Allelopathy
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Predation
When a member of one species (the predator) feeds directly
on all or part of a member of another species (the prey)
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Parasitism
When one organism (the parasite) feeds on the body of, or
the energy used by, another organism (the host), usually by
living on or in the host.
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Look away. Bot Fly picture coming…
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Oh dear, look away. Guinea Worm picture
coming…
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Drink Clean Water
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Mutualism
An interaction that benefits both species by providing each
with food, shelter, or some other resource.
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Commensalism
An association between two organisms in which one benefits and
the other derives neither benefit nor harm.
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Interspecific Competition
When members of two or more species interact to gain
access to the same limited resources (food, light, space)
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Allelopathy
A biological phenomenon by which an organism produces
one or more biochemicals that influence the growth,
survival, and reproduction of other organisms.
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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.
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Some Species Evolve Ways to Share
Resources
Resource partitioning
Reduce niche overlap
Use shared resources at different
• Times
• Places
• Ways
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Fig. 5-7, p. 107
Resource use
Resource use
Species 1 Species 2
Nu
mb
er
of
ind
ivid
ua
ls
Region
of
niche overlap
Species 2Species 1
Nu
mb
er
of
ind
ivid
uals
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Sharing the Wealth: Resource
Partitioning
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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.
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Populations Have Certain
Characteristics (1)
Populations differ in
• Distribution
• Numbers
• Age structure
Population dynamics – The study of how
populations change in response to
environmental changes.
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Populations Have Certain
Characteristics (2)
Changes in population characteristics due to:
• Temperature
• Presence of disease organisms or harmful
chemicals
• Resource availability
• Arrival or disappearance of competing species
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Most Populations Live Together in
Clumps or Patches (1)
Population distribution
• Clumping
• Uniform dispersion
• Random dispersion
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Most Populations Live Together in
Clumps or Patches (2)
Why clumping?
• Species tend to cluster where resources are
available
• Groups have a better chance of finding clumped
resources
• Protects some animals from predators
• Packs allow some to get prey
• Temporary groups for mating and caring for
young
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Populations Can Grow, Shrink, or
Remain Stable (1)
Population size governed by
• Births
• Deaths
• Immigration
• Emigration
Population change =
(births + immigration) – (deaths + emigration)
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Populations Can Grow, Shrink, or
Remain Stable (2)
Age structure
• Pre-reproductive age
• Reproductive age
• Post-reproductive age
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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
• Reproduce early in life
• Have short generation times
• Can reproduce many times
• Have many offspring each time they reproduce
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No Population Can Grow Indefinitely:
J-Curves and S-Curves (2)
Size of populations limited by
• Light
• Water
• Space
• Nutrients
• Exposure to too many competitors, predators or infectious diseases
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No Population Can Grow Indefinitely:
J-Curves and S-Curves (3)
Environmental resistance – Combination of
factors that limit population growth.
Carrying capacity (K) – Maximum population
a habitat can support.
Exponential growth – Indefinite population
growth.
Logistic growth – Growth rate drops as
environmental resistance increases.
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No Population Can Continue to Increase
in Size Indefinitely
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Fig. 5-11, p. 111
Biotic
potential
Po
pu
lati
on
siz
e
Time (t)
Carrying capacity (K)
Environmental
resistance
Population stabilizes
Exponential
growth
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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
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Exponential Growth, Overshoot, and
Population Crash of a Reindeer
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Fig. 5-13, p. 112
2,000
Carrying
capacity
1910 1920 1930 1940 1950
Nu
mb
er
of
rein
deer
Population
overshoots
carrying
capacity
Population
crashes
0
500
1,000
1,500
Year
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Species Have Different Reproductive
Patterns
r-Selected species, opportunists
• Many, small offspring, very little parental
care/protection.
K-selected species, competitors
• Reproduce later in life, small number of
offspring with long lifespans, more parental
care/protection.
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Genetic Diversity Can Affect the Size
of Small Populations
Founder effect – A few individuals colonize a
new, geo-isolated habitat.
Demographic bottleneck – Only a few
individuals survive a catastrophe.
Genetic drift – Lack of genetic diversity
leading to one “set” of genes dominating the
population.
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Genetic Diversity Can Affect the Size
of Small Populations
Inbreeding – Related individuals mating with
one another.
Minimum viable population size – The
number of individuals a population needs to
survive long-term.
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Under Some Circumstances Population
Density Affects Population Size
Density-dependent population controls
• Predation
• Parasitism
• Infectious disease
• Competition for resources
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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
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Population Cycles for the Snowshoe
Hare and Canada Lynx
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Humans Are Not Exempt from Nature’s
Population Controls
Ireland
• Potato crop in 1845
Bubonic plague
• Fourteenth century
AIDS
• Global epidemic
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5-4 How Do Communities and Ecosystems
Respond to Changing Environmental
Conditions?
Concept 5-4 The structure and species
composition of communities and ecosystems
change in response to changing environmental
conditions through a process called ecological
succession.
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Communities and Ecosystems Change
over Time: Ecological Succession
Natural ecological restoration
• Primary succession
• Secondary succession
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Some Ecosystems Start from Scratch:
Primary Succession
No soil in a terrestrial system
No bottom sediment in an aquatic system
Early successional plant species, pioneer
Midsuccessional plant species
Late successional plant species
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Primary Ecological Succession
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Fig. 5-16, p. 116
Exposed
rocks
Lichens and
mosses
Small herbs
and shrubs
Heath mat
Jack pine,
black spruce,
and aspen
Balsam fir,
paper birch, and
white spruce
forest community
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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
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Natural Ecological Restoration of
Disturbed Land
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Fig. 5-17, p. 117
Annual
weeds
Perennial
weeds and
grasses
Shrubs and
small pine
seedlings
Young pine forest
with developing
understory of oak
and hickory trees
Mature oak and
hickory forest
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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• Fires
• Hurricanes
• Clear-cutting of forests
• Plowing of grasslands
• Invasion by nonnative species
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Succession Doesn’t Follow a
Predictable Path
Traditional view
• Balance of nature and a climax community
Current view
• Ever-changing mosaic of patches of vegetation
• Mature late-successional ecosystems
• State of continual disturbance and change
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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
Tipping point