Transcript of 27 Community Interactions. Why Are Community Interactions Important? As community interactions limit...
- Slide 1
- 27 Community Interactions
- Slide 2
- Why Are Community Interactions Important? As community
interactions limit population size, they shape the bodies and
behaviors of the interacting populations Coevolution
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- Why Are Community Interactions Important? The major community
interactions: These interactions can be classified according to
whether each of the species is harmed or helped by the
interaction
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- How Does the Ecological Niche Influence Competition? Each
species occupies a unique ecological niche that encompasses all
aspects of its way of life An ecological niche includes all
physical environmental conditions necessary for survival and
reproduction of a given species
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- How Does the Ecological Niche Influence Competition? The
physical and environmental conditions can include Nesting or
denning sites Climate Type of nutrients the species requires
Optimal temperature range Amount of water needed The pH and
salinity of the water or soil The degree of sun or shade it can
tolerate
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- How Does the Ecological Niche Influence Competition? The niche
also encompasses the entire role that a given species performs
within an ecosystem What the species eat and the other species with
which it competes No two species ever occupy exactly the same
ecological niche within the same natural community, just as no two
organisms can occupy exactly the same physical space at the same
time (competitive exclusion principle)
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- How Does the Ecological Niche Influence Competition?
Competition occurs whenever two organisms attempt to use the same,
limited resources Interspecific - The greater the overlap between
the ecological niches of the two species, the greater the amount of
competition between them Detrimental to all species involved
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- How Does the Ecological Niche Influence Competition? The
competitive exclusion principle Leads to the hypothesis that if a
researcher forces two species with very similar niches to compete
for the same limited resource, one will outcompete the other, and
the species that is well less adapted to the experimental
conditions will die out
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- Figure 27-1 Competitive exclusion Grown in separate flasks
population density Grown in the same flask days 0 2 46 8 10 12 14
16 18 20 22 24 P. aurelia P. caudatum 100 200 50 0 150 100 200 50
150 0 0 2 46 8 10 12 14 16 18 20 22 24
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- How Does the Ecological Niche Influence Competition? The
competitive exclusion principle Gause repeated the experiment,
replacing P. caudatum with P. bursaria, which fed mostly on
bacteria that had settled to the bottom of the test tube These two
species of Paramecium were able to coexist indefinitely because
they preferred feeding in different places, and thus occupied
slightly different niches
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- How Does the Ecological Niche Influence Competition?
Adaptations reduce the overlap of ecological niches among
coexisting species Ecologist Robert MacArthur observed five species
of North American warbler These birds all hunt for insects and nest
in the same type of eastern spruce tree
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- How Does the Ecological Niche Influence Competition?
Adaptations reduce the overlap of ecological niches among
coexisting species (continued) MacArthur found that each species
concentrates its search for food in specific regions within spruce
trees, employs different hunting tactics, and nests at a slightly
different time By dividing up the resources provided by the spruce
trees they share, the warblers minimize the overlap of their niches
and reduce interspecific competition
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- How Does the Ecological Niche Influence Competition?
Adaptations reduce the overlap of ecological niches among
coexisting species (continued) When species with largely similar
ecological niches coexist and compete, each species occupies a
smaller niche than it would by itself, a phenomenon called resource
partitioning Yellow-rumped warbler Bay-breasted warbler
Blackburnian warbler Cape May warbler Black-throated green
warbler
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- How Does the Ecological Niche Influence Competition?
Competition among species may reduce the population size and
distribution of each Although natural selection can reduce niche
overlap, interspecific competition may still restrict the size and
distribution of competing populations Barnacles of the genus
Chthamalus share rocky ocean shores with barnacles of the genus
Balamus Their niches overlap considerably Both live in the
intertidal zone, an area of the shore that is alternately covered
and exposed by the tides
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- How Does the Ecological Niche Influence Competition?
Competition among species may reduce the population size and
distribution of each (continued) Chthamalus dominates the upper
intertidal zone and Balamus dominates the middle intertidal zone
The middle habitat is suitable for both species When Connell
scraped off Balamus, the Chthamalus population increased, spreading
downward into the middle intertidal region where its competitor had
been scraped off This demonstrated that Chthamalus would occupy the
middle intertidal zone if it didnt have to cope with competition
from Bamalus, a larger, faster-growing barnacle
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- How Does the Ecological Niche Influence Competition?
Competition within a species is a major factor controlling
population size Intraspecific competition is the most intense form
of competition because all of the members of the species occupy the
same niche Intraspecific competition is one of the main factors
driving evolution by natural selection Individuals that are better
equipped to obtain scarce resources are more likely to reproduce
successfully, passing their heritable traits to their
offspring
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Although predators are often regarded as being
carnivores (animals that eat other animals), ecologists sometimes
include herbivores (animals that eat plants) in this general
category Long-eared batEagle owlPika
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Predators are generally less abundant than their prey
In order to survive, predators must feed and prey must avoid
becoming food Predator and prey populations exert intense selective
pressure on one another, resulting in coevolution As prey become
more difficult to catch, predators must become more adept at
hunting Some predators and prey have evolved counteracting
behaviors
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Some predators and prey have evolved counteracting
behaviors Bats use sonar to find their prey Some moths (a favorite
prey of bats) have evolved ears that are particularly sensitive to
the pitches used by echolocating bats The moth takes evasive action
after hearing the sound Some moths produce their own high frequency
clicks to interfere The bats have evolved the ability to counter
this defense by switching the frequency of their sound pulses from
the moths sensitivity range or just following the moths clicks
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Predator and prey may engage in chemical warfare May
be used to attack or defend Many plants synthesize toxic and
distasteful chemicals As plants evolved these defensive toxins,
certain insects evolved increasingly efficient ways to detoxify or
even use these substances Nearly every toxic plant is eaten by at
least one type of insect
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Chemical warfare example: Monarch butterflies lay
their eggs on milkweed When their larvae hatch, they consume this
poisonous plant The caterpillars store the poison in their tissues
as a defense against their own predators The stored toxin is
retained in the metamorphosed monarch butterfly Viceroy butterflies
use a similar strategy, storing a bitter compound from willows
(eaten by the larvae) in the tissues of the adult
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Camouflage Both predators and prey have evolved
colors, patterns, and shapes that resemble their surroundings A
camouflaged horned lizard Sand dab fish adjust camouflage to
different backgrounds
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- Figure 27-6 Camouflage by resembling specific objects Leafy sea
dragon Living rock cacti Citrus swallowtail larva Thorn
treehoppers
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Camouflage Predators that ambush prey are aided by
camouflage A camouflaged snow leopardA camouflaged frogfish
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Some prey animals have evolved very differently,
exhibiting bright warning coloration These animals may taste bad,
inflict a venomous sting or bite (as bees or coral snakes do), or
produce a big stink when bothered
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Mimicry Mimicry refers to members of one species
having evolved to resemble another species Two or more distasteful
species may each benefit from a shared warning coloration pattern
(Mllerian mimicry) Predators need only experience one distasteful
species to learn to avoid all with that color pattern
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Mllerian mimicry Toxic monarch and viceroy butterflies
have similar wing patterns; if a predator becomes ill from eating
one species, it will avoid the other Monarch (distasteful) Viceroy
(distasteful)
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Mimicry (continued) Once warning coloration evolved,
there arose a selective advantage for harmless animals to resemble
venomous ones, an adaptation called Batesian mimicry
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- Bee (venomous) Hoverfly (nonvenomous) Batesian mimicry How Do
Predator-Prey Interactions Shape Evolutionary Adaptations? Coral
snake (venomous) Scarlet king snake (nonvenomous)
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Startle coloration Used to deter predators These
animals may have spots that resemble the eyes of a larger animal If
a predator gets close, the prey will flash its eyespots, startling
the predator and allowing the prey to escape False-eyed frog
Peacock moth Swallowtail caterpillar
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? A sophisticated variation of startle coloration
Snowberry flies, which are hunted by territorial jumping spiders
When a spider approaches, the fly spreads its wings and moves them
in a jerky dance Snowberry fly (prey) Jumping spider
(predator)
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- How Do Predator-Prey Interactions Shape Evolutionary
Adaptations? Aggressive mimicry Predators entice their prey to come
close by resembling something attractive For example, by using a
rhythm of flashes that is unique to each species, female fireflies
attract males to mate The frogfish is not only camouflaged but
exhibits aggressive mimicry by dangling a wriggling lure that
resembles a small fish just above its mouth
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- What Are Parasitism and Mutualism? Parasites live in or on
their prey, which are called hosts, usually harming or weakening
them but not immediately killing them Some parasite-host
relationships are symbiotic; that is, the relationships involve a
close, long-term physical association between the participating
species Parasites are generally much smaller and more numerous than
their hosts Examples include tapeworms, fleas, ticks, and many
types of disease-causing protists, bacteria, and viruses
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- What Are Parasitism and Mutualism? Mutualism refers to
interactions between species in which both benefit Many mutualistic
relationships are symbiotic and involve a close, long-term physical
association between the participating species For example, lichens
receive support and protection from fungus while obtaining food
from the photosynthetic alga Lichen Clownfish
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- What Are Parasitism and Mutualism? Mutualistic interactions
Many mutualistic relationships are not intimate and extended, and
so are not symbiotic For example, the relationship between plants
and the insects that pollinate them is not symbiotic The insects
fertilize the plants by carrying plant sperm, and benefit by
sipping nectar and sometimes eating pollen
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- How Do Keystone Species Influence Community Structure? In some
communities, a keystone species plays a major role in determining
community structure A keystone species role is out of proportion to
its abundance in the community If a keystone species is removed
from the community, normal community interactions are significantly
altered and the relative abundance of other species changes
dramatically
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- How Do Keystone Species Influence Community Structure? In the
African savanna, the African elephant is a keystone predator By
grazing on small trees and bushes, elephants prevent the
encroachment of forests and help maintain the grassland community,
along with its diverse population of grazing mammals and their
predators Wolves and cougars Maintain deer populations Maintains
vegetation populations Provides food, nesting, & shelter
African elephant
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- How Do Keystone Species Influence Community Structure?
Identifying a keystone species can be a difficult task Many have
been recognized only after their loss has had dramatic, unforeseen
consequences The intricate and tangled web of community
interactions is beautifully illustrated by the plight of the
northern sea otter in the Aleutian Islands of southwestern Alaska
Kelp forests flourished around islands in waters where the otters
were abundant No otters increased sea urchins No kelp forest
eliminate diversity Northern sea otter
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- Review 1.Which is more intense for niches: interspecific or
intraspecific competition? Why? 2.Define camouflage. 3.What is the
difference between Mullerian and Batesian mimicry? 4.What is a
symbiotic relationship? 5.Define mutualism. 6.What is a keystone
species?