Transcript Biodiversity, Species Interactions, and Population Control

Biodiversity, Species
Interactions, and
Population Control
Chapter 5
Case Study- Southern Sea
Otter
Why is the sea otter considered a keystone species?
Section 5-1
HOW DO SPECIES INTERACT?
Most species compete with one
another for certain resources
• There are five basic types of interaction between species when
they share limited resources:
– Interspecific competition occurs when two or more species interact to
gain access to the same limited resources.
– Predation occurs when a member of one species (predator) feeds
directly on all or part of a member of another species (prey).
Symbiosis= close, long term association 2 or more species: 3 types
– Parasitism + - occurs when one organism (the parasite) feeds on
another organism (the host), usually by living on or in the host.
– Mutualism + + is an interaction that benefits both species by providing
each with food, shelter, or some other resource.
– Commensalism + 0 is an interaction that benefits one species but has
little, if any, effect on the other.
Interspecific Competition
• Interspecific competition is the most common
interaction between species.
• When two species use the same resource, their
niches overlap.
• Resource partitioning occurs when species
competing for similar scarce resources evolve
specialized traits that allow them to use shared
resources at different times, in different ways, or
in different places.
– e.g. warblers who live in the same trees but have such
specialized feeding niches that they do not compete.
Sharing the wealth
Predation
• Predation occurs when a member of one
species (predator) feeds directly on all or
part of a living organism of another plant
or animal species (prey), forming a
predator-prey relationship.
Avoiding and Defending Against
Predators
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Escape
Senses
Armor
Camouflage
Chemical warfare
Warning coloration
Mimicry
Behavior strategies
Safety in numbers
How Species Avoid Predators
“If it is small and strikingly beautiful, it is probably poisonous. If it is strikingly
beautiful and easy to catch, it is probably deadly.” - E.O Wilson
Span worm
Wandering leaf insect
camouflage
Poison dart frog
Bombardier beetle
Foul-tasting monarch
butterfly
Chemical warfare / Warning
Viceroy butterfly mimics
monarch butterfly
mimicry
Hind wings of io moth
resemble eyes of a
much larger animal
When touched, the
snake caterpillar
changes shape to look
like the head of a snake
Deceptive behavior
Fig. 6-6, p. 116
Coevolution
• occurs when two different species interact
over a long period of time and changes in
the gene pool of one species can lead to
changes in the gene pool of the other.
• Some bats and moths have coevolved.
Parasites
 Parasitism +  Hosts
 Inside or outside of hosts
 Harmful effects on hosts
 Important ecological roles of parasites
Parasitism
Mutualism + +
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Both species benefit
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Pollination
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Benefits include nutrition and protection
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Mycorrhizae - fungi that helps plants extract
nutrients and water from soil
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Gut inhabitant mutualism
Examples of Mutualism
Oxpeckers and black rhinoceros
Mycorrhizae fungi on juniper
seedlings in normal soil
© 2006 Brooks/Cole - Thomson
Clown fish and sea anemone
Lack of mycorrhizae fungi on
juniper seedlings in sterilized soil
Fig. 6-7, p. 117
Commensalism + 0
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Species interaction that benefits one and has
little or no effect on the other
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Example: Small plants growing in shade of
larger plants
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Epiphytes
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Forehead mites
Example of commensalism
Section 5-2
WHAT LIMITS THE GROWTH
OF POPULATIONS?
Population Dynamics: Factors
Affecting Population Size
 Population change = (births + immigration)
– (deaths + emigration)
 Age structure (stages)
 Age and population stability
Limits on Population Growth
 Biotic potential
(capacity for growth)
 Intrinsic rate of increase (r) (assumes unlimited resources)
 No indefinite population growth
 Environmental resistance= all the factors that limit population
growth
 Carrying capacity (K) - determined by biotic potential & enviro
resistance
Population Growth Curves
Population size (N)
Environmental
resistance
Carrying capacity (K)
Biotic
potential
Exponential
growth
Time (t)
Fig. 6-11, p. 121
Species have different
reproductive patterns
• Some species have many, usually small,
offspring and give them little or no parental
care or protection.
• Some species have few, usually fairly
large, offspring and invest parental care
and protection.
Reproductive Patterns
 r-selected species
 Opportunists (mostly r-selected)
 Environmental impacts on opportunists
 K-selected species (competitors)
 Intermediate and variable reproductive patterns
r-selected Opportunists and K-selected Species
Fig. 6-15, p. 123
Exponential and Logistic
Population Growth
 Resources control population growth
 Exponential growth - J-shaped curve
 Logistic growth - S-shaped curve
No population can continue to
grow indefinitely
When Population Size Exceeds
Carrying Capacity
 Switch to new resources, move or die
 Overshoots
 Reproductive time lag
 Population dieback or crash
 Human Famines -
Irish potato famine 1845 - 1 million dead
 Factors controlling human carrying capacity- technology
has increased carrying capacity for humans
Exponential growth, overshoot, and population
crash of reindeer introduced onto St. Paul.
Section 5-3
HOW DO COMMUNITIES AND
ECOSYSTEMS RESPOND TO
CHANGING ENVIRONMENTAL
CONDITIONS?
Ecological Succession:
Communities in Transition
 What is ecological succession?
(Gradual change in species composition)
 Primary succession = establishment of communities
on nearly lifeless ground (no soil) ex. glacier retreat, landslide,
lava, abandoned parking lot
 Secondary succession- community disturbed, soil
remains. Burned / cut forests, polluted stream, flood
Primary ecological succession
Animation
Two types of ecological succession animation.
http://www.cengage.com/earthscience/book_content/9781111988937_mi
ller/animations/ch05/animation_media/succession/succession.html
Communities and ecosystems change
over time: Ecological succession
• Secondary succession occurs with a series
of communities or ecosystems with different
species develop in places containing soil or
bottom sediment. Such areas include:
– Abandoned farmland.
– Burned or cut forests.
– Heavily polluted streams.
– Flooded land.
How Predictable is Succession?
 Climax community concept- orderly sequence “Balance of nature”- old school
 New views of equilibrium in nature Unpredictable succession- “The modern view is that we cannot
project the course of a given succession….”
 Natural struggles
Natural ecological restoration of
disturbed land
Living systems are sustained
through constant change
• Living systems contain complex processes that interact
to provide some degree of stability. This capacity to
withstand external stress and disturbance is maintained
by change in response to changing environmental
conditions.
• One aspect of stability is inertia, or persistence, which is
the ability of a living system, such as a grassland or
forest, to survive moderate disturbances.
• A second aspect of stability is resilience, which is the
ability of a living system to be restored through
secondary succession after a more severe disturbance.
Three big ideas
• Certain interactions among species affect
their use of resources and their population
sizes.
• There are always limits to populations
growth in nature.
• Changes in environmental conditions cause
communities and ecosystems to gradually
alter their species composition and
population sizes (ecological succession).