Transcript Chapter 8 Community Ecology Chapter Overview Questions • What determines the number of species in a community? • How can we classify species according.

Chapter 8
Community Ecology
Chapter Overview Questions
• What determines the number of species in a
community?
• How can we classify species according to their
roles in a community?
• How do species interact with one another?
• How do communities respond to changes in
environmental conditions?
• Does high species biodiversity increase the
stability and sustainability of a community?
Core Case Study:
Why Should We Care about the
American Alligator?
• Hunters wiped out
population to the
point of near
________.
• Alligators have
important ecological
role.
Core Case Study:
Why Should We Care about the
American Alligator?
• Dig deep depressions (__________).
– Hold water during dry spells, serve as refuges for
aquatic life.
• Build _________ _________.
– provide nesting and feeding sites for birds.
– Keeps areas of open water free of vegetation.
• Alligators are a __________ species:
– Help maintain the structure and function of the
communities where it is found.
COMMUNITY STRUCTURE AND
SPECIES DIVERSITY
• Biological communities differ in their structure
and physical appearance.
Tropical
rain forest
Coniferous
forest
Deciduous
forest
Thorn
forest
Thorn
scrub
Tall-grass Short-grass Desert
scrub
prairie
prairie
Species Diversity and Niche
Structure: Different Species Playing
Different Roles
• Biological communities differ in the types and
numbers of species they contain and the
ecological roles those species play.
– Species __________ the number of different species
it contains (species __________) combined with the
abundance of individuals within each of those species
(species _________).
Species Diversity and Niche Structure
• Niche structure: how many potential
__________ _______occur, how they
resemble or differ, and how the species
occupying different niches interact.
• Geographic location: species _______ is
highest in the tropics and declines as we move
from the ________ toward the _______.
TYPES OF SPECIES
• Native, nonnative, indicator, keystone, and
foundation species play different ecological
roles in communities.
– _________ ________: those that normally live
and thrive in a particular community.
– __________ _______: those that migrate,
deliberately or accidentally introduced into a
community.
Case Study:
Species Diversity on Islands
• MacArthur and Wilson proposed the species
equilibrium model or ______ __ _______
___________ in the 1960’s.
• Model projects that at some point the rates of
immigration and extinction should reach an
__________ based on:
– Island size
– Distance to nearest mainland
Indicator Species:
Biological Smoke Alarms
• Species that serve as ______ ________ of
damage to a community or an ecosystem.
– Presence or absence of trout species because they
are sensitive to temperature and oxygen levels.
Keystone Species: Major Players
• Keystone species help determine the _____ and
________ of other species in a community
thereby helping to sustain it.
Foundation Species:
Other Major Players
• Expansion of keystone species category.
• Foundation species can ______ and
______habitats that can benefit other species in
a community.
– _________ push over, break, or uproot trees, creating
forest openings promoting grass growth for other
species to utilize.
Case Study:
Why are Amphibians Vanishing?
• Frogs serve as indicator species because different
parts of their life cycles can be easily disturbed.
Adult frog
(3 years)
Young frog
Sperm
Tadpole develops
into frog
Sexual
Reproduction
Eggs
Fertilized egg
development
Tadpole
Egg hatches
Organ formation
Case Study:
Why are Amphibians Vanishing?
•
•
•
•
•
•
•
•
Habitat loss and __________.
Prolonged ________.
Pollution.
Increases in ________ _______.
Parasites.
______and _______ diseases.
Overhunting.
Natural _________ or deliberate _________ of
nonnative predators and competitors.
Video: Frogs Galore
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VIDEO
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Living in the Environment.
• Do we have an ethical obligation to protect shark species
from premature extinction and treat them humanely?
– a. No. It's impractical to force international laws on
individual fishermen that are simply trying to feed their
families with the fishing techniques that they have.
– b. Yes. Sharks are an important part of marine ecosystems.
They must be protected and, like all animals, they should
be humanely treated.
SPECIES INTERACTIONS:
COMPETITION AND PREDATION
• Species can ________ through competition,
predation, parasitism, mutualism, and
commensalism.
• Some species ________ __________that allow
them to reduce or avoid competition for
resources with other species (________
__________).
Resource Partitioning
• Each species _________
competition with the others
for _______ by spending at
least half its feeding time in a
distinct portion of the spruce
tree and by consuming
somewhat ________ ______
_______.
Niche Specialization
• Niches become
separated to avoid
________ for
_______.
Number of individuals
Number of individuals
Species 1
Species 2
Region
of
niche overlap
Resource use
Species 1
Resource use
Species 2
SPECIES INTERACTIONS:
COMPETITION AND PREDATION
• Species called ________ feed on other species
called prey.
• Organisms use their _________to locate objects
and ______ and to attract pollinators and mates.
• Some _________ are fast enough to catch their
______, some hide and lie in wait, and some inject
_________ to paralyze their prey.
PREDATION
• Some prey escape
their predators or
have outer
protection, some are
________, and some
use chemicals to
repel predators.
(a) Span worm
(b) Wandering leaf insect
(c) Bombardier beetle
(d) Foul-tasting monarch butterfly
(e) Poison dart frog
(f) Viceroy butterfly mimics
monarch butterfly
(g) Hind wings of Io moth
resemble eyes of a much
larger animal.
(h) When touched, snake
caterpillar changes shape to
look like head of snake.
SPECIES INTERACTIONS: PARASITISM,
MUTUALISM, AND COMMENSALIM
• _________ occurs when one species feeds on
part of another organism.
• In _________, two species interact in a way that
benefits both.
• __________ is an interaction that benefits one
species but has little, if any, effect on the other
species.
Parasites: Sponging Off of Others
• Although _________ can harm their hosts,
they can promote community ________.
– Some _________ live in host (microorganisms,
tapeworms).
– Some parasites live outside _______ (fleas, ticks,
mistletoe plants, sea lampreys).
– Some have little contact with host (dump-nesting
birds like cowbirds, some duck species)
_________: Win-Win Relationship
• Two species can
interact in ways
that benefit both
of them.
(a) Oxpeckers and black rhinoceros
(b) Clownfish and sea anemone
(c) Mycorrhizal fungi on juniper seedlings in
normal soil
(d) Lack of mycorrhizal fungi on juniper seedlings
in sterilized soil
___________: Using without Harming
• Some species
interact in a way
that helps one
species but has
little or no effect
on the other.
ECOLOGICAL SUCCESSION:
COMMUNITIES IN TRANSITION
• New environmental conditions allow one group
of species in a community to replace other
groups.
• Ecological _________: the gradual change in
species composition of a given area
– _________ ________: the gradual establishment of
biotic communities in lifeless areas where there is no
soil or sediment.
– _________ _________ : series of communities
develop in places containing soil or sediment.
________Succession:
Starting from Scratch
• Primary
succession begins
with an
essentially lifeless
are where there
is no soil in a
terrestrial
ecosystem
Exposed
rocks
Lichens
and mosses
Secondary Succession:
Starting Over with Some Help
• Secondary
succession
begins in an
area where the
natural
community has
been
disturbed.
Can We Predict the Path of
Succession, and is Nature in Balance?
• The course of succession cannot be precisely
predicted.
• Previously thought that a stable climax
community will always be achieved.
• Succession involves species competing for
enough light, nutrients and space which will
influence it’s trajectory.
ECOLOGICAL STABILITY AND
SUSTAINABILITY
• Living systems maintain some degree of stability
through constant change in response to
environmental conditions through:
– Inertia (persistence): the ability of a living system to
resist being disturbed or altered.
– Constancy: the ability of a living system to keep its
numbers within the limits imposed by available
resources.
– Resilience: the ability of a living system to bounce
back and repair damage after (a not too drastic)
disturbance.
ECOLOGICAL STABILITY AND
SUSTAINABILITY
• Having many different species appears to
increase the sustainability of many communities.
• Human activities are disrupting ecosystem
services that support and sustain all life and all
economies.