Chapter 27 Community Interactions - Linn-Benton Community...
Transcript of Chapter 27 Community Interactions - Linn-Benton Community...
Chapter 27 Community Interactions
Learning Goals for Ch. 27
27.1 Why Are Community Interactions Important?
27.2 What Is the Relationship Between the Ecological
Niche and Competition?
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
27.4 What Is Parasitism?
27.5 What is Mutualism?
27.6 How Do Keystone Species Influence Community
Structure?
27.7 Succession: How Do Community Interactions
Cause Change Over Time?
27.1 Why Are Community Interactions Important?
An ecological community consists of all the
interacting populations within an ecosystem
– A community can encompass the entire biotic,
or living, portion of an ecosystem
– Interactions between populations in a community
help limit their size
Copyright © 2011 Pearson Education Inc. Biology: Life on Earth, 9e
Ecological hierarchy
Biosphere
Ecosystem
Community
Population
Organism
Table 27-1
Type of
Interaction Effect on
Species A Effect on
Species B
Competition between A and B Harms Harms
Predation by A on B Benefits Harms
Parasitism by A on B Benefits Harms
Mutualism between A and B Benefits Benefits
27.1 Why Are Community Interactions Important?
An ecological community consists of all the interacting
populations within an ecosystem (continued)
– The process by which two interacting species act as
agents of natural selection on one another is called
coevolution
Co-Evolution Bull Thorn Acacia and Ants
27.1 Why Are Community Interactions Important?
The most important community interactions are:
– Competition, which harms both species
– Predation, which benefits the predator but harms
the prey
– Parasitism, which benefits parasite but harms the
host
– Mutualism, which benefits both species
27.2 What Is the Relationship Between the
Ecological Niche and Competition?
Each species occupies a unique ecological niche that encompasses all aspects of its way of life
– These include:
– Its physical home or habitat
– The physical and chemical environmental factors necessary for its survival, such as nesting sites, climate, and the type of nutrients it needs
– The role that the species performs within an ecosystem, such as what it eats and the other species with which it competes
– Although different species share aspects of their niche with others, no two species ever occupy exactly the same ecological niche within a community
27.2 What Is the Relationship Between the
Ecological Niche and Competition?
Competition occurs whenever two organism
attempt to use the same, limited resources
– Interspecific competition occurs between
members of different species, if they feed on the
same things or require similar breeding areas
– Ex. Cattle and deer
– Ex.Wild horses and Elk
– Ex. Zebra mussels and native mussels
27.2 What Is the Relationship Between the
Ecological Niche and Competition?
Adaptations reduce the overlap of ecological
niches among coexisting species
– The competitive exclusion principle states that
if two species occupy exactly the same niche
with limited resources, one will outcompete the
other
P. aurelia P. caudatum
(a) Grown in separate flasks
(b) Grown in the same flask
Competitive Exclusion
Fig. 27-1
Resource Partitioning
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
Resource Partitioning
Ecologist Robert MacArthur explored the competitive
exclusion principle by carefully observing five species
of North American warbler
– These birds all hunt for insects and nest in the same type
of eastern spruce tree
– 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
Resource Partitioning
Fig. 27-2
Blackburnian
warbler
Black-throated
green warbler
Cape May
warbler
Bay-breasted
warbler
Yellow-rumped
warbler
Intraspecific Competition
Competition within a species is a major factor controlling population size
– Intraspecific competition, competition between individuals of the same species, is the most intense form of competition
– If resources are limited, this is a major factor controlling population size
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Predator–prey interactions shape evolutionary adaptations
– Predators eat other organisms; these include herbivores (animals that eat plants) as well as carnivores (animals that eat other animals)
–Predators include a grass-eating pika, a bat hunting a moth, and the more familiar example of a hawk eating a bird
– Predators tend to be less abundant than their prey
Forms of Predation
Fig. 27-3
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
– Bat and moth adaptations provide excellent examples of how body structures and behaviors are molded by competition
– Bats emit high-pitch sound pulses that bounce off their surroundings, allowing them to navigate and detect prey
– Moths (their prey) have evolved ears sensitive to the pitch of sounds the bats emit, and they take evasive actions in response
– The bats, in turn, counter by switching the frequency of their sound pulses away from the moth’s sensitivity range
Bat-Moth Coevolution
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Camouflage conceals both predators and their
prey
– Camouflage renders animals inconspicuous
even when in plain sight
–Predators and prey have evolved colors,
patterns, and shapes that resemble their
surroundings
Camouflage by Blending In
Fig. 27-4
Camouflage
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Camouflage conceals both predators and their
prey (continued)
– To avoid detection by predators, some animals
have evolved to resemble objects, such as
leaves, twigs, seaweed, thorns, or even bird
droppings
– Some plants have evolved to resemble rocks to
avoid detection by herbivores
Camouflage by Resembling Specific Objects
Fig. 27-5a, b
Camouflage by Resembling Specific Objects
Fig. 27-5c, d
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Camouflage conceals both predators and their
prey (continued)
– Camouflage also helps predators ambush their
prey
–Examples include the cheetah blending with
tall grass and the frogfish resembling a rock
Camouflage Assists Predators
Fig. 27-6
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Bright colors often warn of danger
– Some animals have evolved bright warning
coloration that attracts the attention of potential
predators
–Warning coloration advertises that the animal
is bad-tasting or poisonous before the
predator attacks
–Examples include poison arrow frogs, coral
snakes, and honey bees
Warning Coloration
Fig. 27-7
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Some prey organisms gain protection through mimicry
– Mimicry refers to when members of one species have
evolved to resemble another species
– Two or more distasteful species may each benefit from a
shared warning coloration pattern (Müllerian mimicry)
– Predators need only experience one distasteful
species to learn to avoid all with that color pattern
– For example, toxic monarch and viceroy butterflies
have similar wing patterns; if a predator becomes ill
from eating one species, it will avoid the other
Mullerian Mimicry
Fig. 27-8
Batesian Mimicry
Fig. 27-9a, b
Batesian Mimicry
Fig. 27-9c, d
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Some prey organisms gain protection through mimicry (continued)
– Some animals deter predators by employing startle coloration
–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
–Examples include the peacock moth and the swallowtail caterpillar
Startle Coloration
Fig. 27-10
27.3 What Are the Results of Interactions Between
Predators and Their Prey?
Predators may use mimicry to attract prey
– In aggressive mimicry, a predator resembles a
harmless animal or part of the environment, to
lure prey within striking distance
–For example, a frogfish dangles a wriggling
lure that attracts a curious fish that is then
eaten
Aggressive Mimicry
Fig. 27-6b
Predators and prey may engage in chemical
warfare
– Predators and prey use toxins for attack and
defense
–The bombardier beetle sprays boiling-hot
chemicals from its abdomen onto its attacker
Chemical Warfare
Fig. 27-12a
Predators and prey may engage in chemical
warfare for attack and defense (continued)
– Many plants have evolved chemical adaptations
that deter their herbivore predators, such as the
milkweed
– In the case of the milkweed, however,
monarch butterfly caterpillars have evolved to
tolerate the toxins and store them in their
tissues as a defense against predation
Chemical Warfare
Fig. 27-12b
Parasites live in or on their prey, which are
called hosts, usually harming or weakening
them but not immediately killing them
– 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
Social parasites!
Animals that take advantage of the social
behavior of a host to complete their life cycle.
27.5 What Is Mutualism?
Mutualism refers to interactions between
species in which both benefit
–For example, lichens form a mutualistic
relationship between a fungus and an algae
–The fungus provides support and protection
while obtaining food from the
photosynthetic alga
Not Moss but Lichen
27.5 What Is Mutualism?
Mutualism refers to interactions between
species in which both benefit (continued)
– Another example of mutualism is the clownfish
and sea anemones
–The clownfish takes shelter from predators
among the venomous tentacles of an
anemone, while in turn cleaning it, providing it
with scraps of food, and defending it from
predators
Mutualism
Fig. 27-13b
Mutualisms
Obligatory:
Yucca plants and
Yucca moths
27.6 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
– Keystone species need to be identified and protected so that human activities do not lead to the collapse of entire communities and ecosystems
Keystone Species
Fig. 27-14a
Sea Otter as a Keystone Species