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ENVIRONMENTAL SCIENCE 13e
CHAPTER 5:
Biodiversity, Species
Interactions, and
Population Control
Fig. 5-1, p. 79
Fig. 5-1, p. 79
Homework
watch video
• http://www.youtube.com/watch?v=Wcyi_IJH9Y
Core Case Study: Endangered
Southern Sea Otter (1)
• Santa Cruz to Santa Barbara shallow
coast
• Live in kelp forests
• Eat shellfish
• ~16,000 around 1900
• Hunted for fur and because considered
competition for abalone and shellfish
Core Case Study: Endangered
Southern Sea Otter (2)
• 1938-2008: increase from 50 to ~2760
• 1977: declared an endangered species
Keystone species: plays a role affecting
many other organisms in ecosystem
specifically sea otters eat sea urchins that
would otherwise destroy kelp forests
Kelp forests provide essential habitat for
entire ecosystem
Science Focus: Sea Urchins
Threaten Kelp Forests (1)
• Kelp forests
– Can grow two feet per day
– Require cool water
– Host many species – high biodiversity
– Fight beach erosion
– Algin
Science Focus: Sea Urchins
Threaten Kelp Forests (2)
• Kelp forests threatened by
– Sea urchins
– Pollution
– Rising ocean temperatures
• Southern sea otters eat urchins
– Keystone species
Fig. 5-A, p. 82
5-1 How Do Species Interact?
• Concept 5-1 Five types of species
interactions affect the resource use
and population sizes of the species in
an ecosystem.
Species Interact in 5 Major Ways
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•
•
•
•
Interspecific competition
Predation
Parasitism
Mutualism
Commensalism
In Class Assignment:
What are the 5 major ways species interact?
Define each
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Interspecific competition
Predation
Parasitism
Mutualism
Commensalism
Interspecific Competition
• No two species can share vital limited
resources for long
• Resolved by:
– Migration
– Shift in feeding habits or behavior
– Population drop
– Extinction
• Intense competition leads to
resource partitioning
Resource Partitioning of 5 species of insect eating warblers
Blackburnian
Warbler
Black-throated
Green Warbler
Cape May
Warbler
Bay-breasted
Warbler
Yellow-rumped
Warbler
Stepped Art
Fig. 5-2, p. 81
Predation (1)
• Predator strategies
– Herbivores can move to plants
– Carnivores
• Pursuit
• Ambush
– Camouflage
– Chemical warfare
Predation (2)
• Prey strategies
– Evasion
– Alertness – highly developed senses
– Protection – shells, bark, spines, thorns
– Camouflage
Predation (3)
• Prey strategies, continued
– Mimicry
– Chemical warfare
– Warning coloration
– Behavioral strategies – puffing up
Ways in which prey species avoid their predators
Camouflage
(a) Span worm
(b) Wandering leaf insect
Fig. 5-3, p. 83
Chemical Warfare
Warning coloration
(c) Bombardier beetle
(d) Foul-tasting monarch butterfly
Fig. 5-3, p. 83
Chemical warfare; warning coloration
(e) Poison dart frog
Mimicry
(f) Viceroy butterfly mimics
monarch butterfly
Fig. 5-3, p. 83
Deceptive looks
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
Deceptive behavior
(h) When touched,
snake caterpillar changes
shape to look like head of snake.
Fig. 5-3, p. 83
Coevolution
• Predator and prey
– Intense natural selection pressure on
each other
– Each can evolve to counter the
advantageous traits the other has
developed
– Bats and moths
Fig. 5-4, p. 83
Parasitism
• Live in or on the host
• Parasite benefits, host harmed
• Parasites promote biodiversity
Fig. 5-5, p. 84
Fig. 5-5, p. 84
Relationships often more complicated than
they first seem
• Mistletoe a parasite and a keystone
species?
• http://news.nationalgeographic.com/news/
2007/12/071224-mistletoe-research.html
Mutualism
• Both species benefit
• Nutrition and protection
• Gut inhabitant mutualism
Fig. 5-6, p. 85
Fig. 5-6, p. 85
Commensalism
• Benefits one species with little impact
on other
Fig. 5-7, p. 85
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.
Limits to Population Growth (1)
• Biotic potential is idealized capacity for growth
– Ex. With no controls on pop growth a species of bacteria that can
reproduce every 20 minutes would generate enough offspring to form a
layer 1 foot deep over the entire earth’s surface in just 36 hrs
• Intrinsic rate of increase (r):rate at which a
population could grow if it had unlimited resources
• Nature limits population growth with resource limits and
competition
• Environmental resistance: the combination of all factors
that act to limit the growth of a population
• Carrying capacity: the max pop of a given species that
a particular habitat can support indefinitely
Limits to Population Growth (1)
• Exponential growth- starts slowly but then accelerates as the pop
increases because the base size of the pop is increasing (J shaped
curve)
• Logistic growth- growth rate decreases as the pop becomes
larger and faces environmental resistance ; over time , the pop
size stabilizes at or near the carrying capacity of its
environment which results in a sigmoid (S shaped) population
growth curve
Overshoot and Dieback
• Population not transition always smooth from
exponential to logistic growth
• Overshoot carrying capacity of environment
• Caused by reproductive time lag (the time needed for the
birth rate to fall and the death rate to rise in response to
resource overconsumption)
• Dieback (Population Crash), unless excess individuals
switch to new resource
Different Reproductive Patterns
• r-Selected species
– Many, usually small offspring, give them little parental
care or protection
– These species overcome massive losses of offspring
by producing so many that a few will likely survive to
begin to reproduce again
• K-selected species
– Slowly reproducing, reproduce later in life, ex.
Mammals offspring develop inside mother’s body’s
where they are safe, parents devote much time to
care of young
• Most species’ reproductive cycles between two extremes
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.
Ecological Succession: gradual change in
species composition in a given area
• Primary succession-involves the gradual establishment
of biotic communities in lifeless areas where there is no soil in
a terrestrial ecosystem or no bottom sediment in an aquatic
ecosystem
• Secondary succession- contains soil or sediment
• Disturbances create new conditions
Succession’s Unpredictable
Path
• Successional path not always predictable
toward climax community
• Communities are ever-changing mosaics
of different stages of succession
• Continual change, not permanent
equilibrium
• Inertia, persistence (the ability of a living system
such as a forest or grassland to survive
moderate disturbances)
• Resilience the ability of a living system to be
restored thru secondary succession after a more
severe disturbance
• Ecological tipping point
• Tropical rain forests vs less diverse tropical
grasslands
Succession at Mt. St. Helens
• http://news.nationalgeographic.com/n
ews/2005/05/0513_050513_mountsth
elens.html
• http://ngm.nationalgeographic.com/20
10/05/mount-st-helens/funk-text