Transcript Chapter 5: Interactions in the Ecosystem

Chapter 5: Interactions in the Ecosystem
5.1 Habitats and Niches
5.2 Evolution and Adaptation
5.3 Populations
Objectives
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Describe the concept of the niche.
Examine how interactions between a
species and its environment define the
specie’s niche.
Chapter 5:
Interactions in the Ecosystem
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An ecosystem is a network of living and
nonliving things.
Organisms are connected by food webs and
by their common needs.
All organisms need:
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A. Food and Energy
B. Water
C. Living Space
D. Appropriate Climate
Interactions in the Ecosystem
(cont.)
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All species have evolved different ways of
gathering resources from their environment.
Evolution ties together biology and the physical
world as ecology ties together the interactions
between living and nonliving things.
Therefore, the study of ecosystems is also the
study of evolution
5.1 Habitats and Niches
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Ecosystems can be extremely large; containing
many square kilometers and many different
organisms.
Environments within an ecosystem vary: the
environment by a stream is different than the
environment in a forest.
The organisms in these different environments
are different from each other. They have adapted
to the conditions in their particular habitat.
Niches
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Niche-the role of an organism in the
ecosystem.
The actions of an organism define its role
in the ecosystem.
A niche is more than just the habitat an
organisms lives in; it is also what that
organism does within its habitat
Niches (cont.)
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A niche includes both the biotic and abiotic
factors.
All the biotic and abiotic factors taken
together define an organisms niche.
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Biotic factors-food source and predators
Abiotic factors-temperature, amount of
sunlight and water
Niches (cont.)
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All members of a species are adapted to the
same niche.
No two species can share the same niche in
the same habitat.
Two species can occupy niches that are very
similar to each other.
Niches (cont.)
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Example: Anolis lizards
The niches of the different species vary only in
the size of the insects they eat.
If two species try to share the same niche in the
same habitat, they will compete for resources.
This could cause the one specie to have to move
to another area or the populations to die out.
Anolis Lizard
Niches (cont.)
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Competitive exclusion: the extinction of a
population due to direct competition with
another species for resources.
Competitive exclusion is the extinction of
one population in one area not the
extinction of a whole species.
Niches (cont.)
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In many ecosystems the niche of one specie
can effect the niche of another specie.
Figure 5.3 p. 74 Barnacles
Barnacles
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Species B (Balanus)was responsible for the niche
of species A (Chthamalus) and when removed A
began to grow further down.
Niches (cont.)
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Fundamental niche-the theoretical niche
Realized niche-the actual niche
Fundamental Niche
Realized Niche
Niche Diversity
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Niche diversity is determined by the abiotic
factors in an ecosystem.
Predator-an organism that actively hunts another
organisms
Prey-the hunted organism
Predators help to increase the diversity of niches
by keeping the population of its prey in check.
This allows resources to be available for other
organisms.
Niche Diversity (cont.)
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Keystone predator- a predator that
promotes a great niche diversity in its
habitat.
Robert Paine and the Sea Stars
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He removed the sea star from a tide pool and
as a result the mussel population increased
until they began to “out compete” the other
species.
The number of species dropped from 15 to 8.
Sea Stars and Tide Pools
Review
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What is a niche?
What effect does a keystone predator have
on niche diversity?
What is the difference between a
fundamental niche and a realized niche?
5.2 Evolution and Adaptation
Objective
Explain
how a species adapts to its niche.
Describe convergent evolution and
coevolution, and relate each to the concept of
niche.
Evolution and Adaptation
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Ecosystems change over time. Mountains
are created and eroded, rivers change
course forest are created and destroyed.
Changes in environment affect the niches
of the organisms in that particular
environment.
Changes in the environment affect the
evolution of populations
Natural Selection
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http://www.pbs.org/wgbh/evolution/educat
ors/course/session4/explore_a.html
Evolution
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Evolutions is a change in the characteristics
of a population of organisms over time.
This occurs when some individuals have
genetic variations that give them an
advantage over other organisms.
Evolution: Online Lessons for Students:
Activity 4- Flashy Fish
Evolving in a Niche
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Evolution causes organisms to evolve to a
certain niche in the environment.
This reduces competition with other
species.
Fig. 5.5 Warblers
Specialized species-Koala
Generalized species-Cockroaches
Convergent Evolution
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Similar ecosystems often have similar niches.
Environmental pressures may then select for
similar adaptations. Resulting in organisms that
may even look alike.
Convergent Evolution- the independent
development of similar adaptations in two species
with similar niches.
Examples: Figure 5.6 and
Convergent Evolution
Convergent Evolution
Coevolution
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Other organisms may play an important role in
the life of an organism.
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Keystone Predators
Species that interact closely may become adapted
to one another through a process called
Coevolution.
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Result from: Feeding relationships and adaptation
for mutual benefits.
Examples:
Coevolution –Yucca Moth and Yucca
Plant
Coevolution
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http://www.pbs.org/wgbh/evolution/library
/01/3/quicktime/l_013_01.html
Review
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How do species adapt to the environment?
What is the difference between coevolution
and convergent evolution?
5.3 Populations
Objectives
Explain how populations of organisms grow.
Describe the factors that limit the growth of a
population.
Identify the shapes of growth curves that
represent populations of different organisms.
5.3 Populations
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The abiotic and biotic factors that define a
niche also limit the growth of a species.
Size of a population can be limited by:
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Lack of food
Predators
Disease
Population Growth
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Thomas Malthus an English economists studied
human population.
He stated:
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Human population can quickly grow past the
environment’s ability to support it.
He felt that famine and disease occurred when
populations became too large.
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Bubonic Plague
Population Growth
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Malthus’s observations influenced a naturalist by
the name of Charles Darwin.
“On the Origin of Species”
“There is no exception to the rule that every
organic being naturally increases at so high a rate,
that, if not destroyed, the Earth would soon be
covered by progeny of a single pair.”
Population Growth
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Important to Darwin’s theories of evolution
was the idea that organisms produce more
offspring than can survive.
Overproduction of offspring causes:
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Selection of the more favorable traits
(survival of the fittest)
Population Growth
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Darwin illustrated overproduction with the
example show in Figure 5.8 p. 80.
Population Growth
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Exponential Growth- population growth in
which the rate of growth in each generation
is a multiple of the previous generation.
Any population has the potential to
increase exponentially if…the perfect
conditions exist
Population Growth
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Although natural population can show
exponential growth, it occurs only for a
short time. This is due to the availability of
resources and restricted geographic areas.
Carrying Capacity
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As a population grows it takes more from the
habitat.
Resources become scarce.
Scarce Resources = Competition
Death rate increases
Birth rate decreases
Growth Slows
Birth rate = Death rate (population growth stops)
Carrying Capacity
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Carrying Capacity- the number of
individuals of a species that can be
supported by an ecosystem
Figure 5.9 p. 81
Limiting Factors
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Forces that slow the growth of a population
are called the limiting factors.
Figure 5.10 p. 82
Examples:
Limiting Factors
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Two kinds of limiting factors
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density dependent limiting factors
density-independent limiting factors
Limiting Factors
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Density dependent limiting factors: dependent on
population size.
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Food supply
Predation
Disease
Parasitism
Living Space
Water Availability
Density dependent factors are related to
competition and other interactions between
organisms
As populations grow these factors have a greater
effect.
Limiting Factors
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Density-independent limiting factors:
affects the same percentage of a population
regardless of its size.
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Climate
Human Disturbances
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Deforestation
Natural Disasters
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Hurricanes
Limiting Factors
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Populations controlled by density dependent
factors show a S-shaped growth curve.
Populations controlled by density-independent
factors show a boom-and-bust curve. This type
of curve represents exponential growth.
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Many insects follow this type of curve.
Figure 5.11 p. 83
S-Shaped Curve
Boom Bust Curve
Population
Human Population
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Human population has long been an exponential
one.
This continuing exponential has continued due to:
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Advances in medicine, technology, agriculture,
energy development, transportation
However, no population can continue this way.
Human population growth will level out as:
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Use up all the available resources
Summary
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What is exponential growth?
What is carrying capacity?
What are the two types of limiting factors?
What has allowed human population to
keeping growing exponentially?