Download Chapter Five: Populations and Communities

Populations and Communities
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Standard 3: Students know and understand
the characteristics and structure of living
things, the processes of life, and how living
things interact with each other and their
environment.
3.16: An organism’s adaptations (for example
structure, behavior) determine its niche (role)
in the environment.
3.16a: Predict the niche of an organism based
on physical and behavioral characteristics.
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Population
Carrying capacity
Predation
Coevolution
Parasitism
Symbiosis
Mutualism
Commensalism
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Niche
Fundamental niche
Realized niche
Competitive exclusion
Keystone species
Videos approximately
55 minutes
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A population is a group
of organisms of the
same species that live in
a specific geographical
area and interbreed.
Population growth is
important because
populations of different
species interact and
affect one another,
including human
populations.
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In the 1850’s two
dozen rabbits were
introduced from
Europe. By the 1950’s
there were 600,000,000
rabbits. What
conditions were
favorable for this
huge growth?
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Whether a population
grows or shrinks
depends on births,
deaths, immigration
and emigration.
Immigration is
movement of
individuals into a
population.
Emigration is the
movement of organisms
out of a population.
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Exponential growth
occurs when numbers
increase by a certain
factor in each successive
time period. This is
indicated by a J-shaped
curve.
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Populations do not
grow unchecked
forever. Eventually due
to food availability,
predators and disease,
the growth will slow
and may stabilize.
The largest population
that an environment can
support at any given
time is called the
carrying capacity.
Density-independent
factors are variables that
affect a population
regardless of population
density, like fires,
floods, weather.
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Logistic growth is
population growth that
starts with a minimum
number of individuals
and reaches a maximum
depending on the
carrying capacity of the
habitat.
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Abiotic factors are nonliving factors that affect
a population. Weather
and climate are the
most important. This
includes water
availability.
Common Abiotic Factors (6:35)
Biotic factors are living
factors. Food,
predators, and human
activity affect
populations.
Biotic Factors (3:57)
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Today, human population is 6.8 billion and
increasing.
Better sanitation, hygiene, disease control and
technology have decreased the rate of death for
human populations. What kind of graph is
this, logistic or exponential?
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Predation is the act of
one organism killing
another for food.
Most animals are both
predator and prey.
Exceptions are very
large species like
killer whales that are
not hunted by other
species.
Predation: (5:00)
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Many interactions
between species are the
result of a long
evolutionary history.
Species that involve
predator-prey or
parasite-host
relationships often
develop adaptations in
response to one another.
This back and forth
evolutionary
adjustment between
two species is called
coevolution.
Evolution coevolution
of the ant and fungi (5:13)
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A parasite is an
organism who is
dependent upon a host.
The host is always
larger than the parasite.
Indian paintbrush
(Castilleja indivisa) is a
parasitic plant that
obtains some of its
nutrients and water
from host plant-bluebonnet (Lupinus
texensis).
Indian paintbrush and bluebonnet
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Herbivores eat plants, but
don’t generally kill them.
However, plants do have
defense mechanisms, like
thorns or chemical
compounds that make
herbivores sick or kill them.
Monarch butterflies have
adapted so they can eat
milkweed that is poisonous
to other animal species,
thus keeping them from
being eaten by birds.
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Mutualism is a
mutually beneficial
relationship between
organisms.
The bee feeds on the
flower and pollinates
it at the same time.
Both benefit.
Coral Reef Ecosystem
Bee and flower
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Whaleshark and remora
Commensalism occurs
when one organism
benefits from another
without aiding or harming
the host.
Remoras are “hitchhiker”
fish that eat the leftovers
of larger fish. They don’t
help or hurt the fish, so
it’s a commensal
relationship.
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When any organism
dies, it is eventually
eaten by detrivores (like
vultures, worms and
crabs) and broken down
by decomposers
(mostly bacteria and
fungi), and the
exchange of energy
continues.
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Where a habitat is the place where an
organism lives, a niche describes
how an organism fits into an
ecosystem.
A fundamental niche is the entire
range of conditions where an
organism or species could survive.
Competition for resources between
species, shapes a species’
fundamental niche.
The actual niche a species occupies is
called the realized niche.
Some species will steal food from one
another—this is called
kleptoparasitism.
Niches (1:33)
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Two species that are too
similar cannot coexist
because one of the
species will be slightly
better at acquiring
resources.
Thus, the less successful
species will either die
off or move away.
One species eliminating
another through
competition is called
competitive exclusion.
Competitive exclusion
and resource Partitioning (4:10)
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Sometimes, competitors
eat the same thing
found in the same place
or fundamental niche.
In some cases, they will
share or divide
resources thus creating
their own smaller,
realized niche.
Example: Birds of the
same species will divide
resources up in various
parts of a tree.
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Interactions between
organisms and the
number of species in an
ecosystem add to the
resiliency of an
ecosystem.
A keystone species is a
species that is critical to
an ecosystem because
the species affects the
survival and number of
many other species in
its community.
Mud Shrimp (3:01)
Sea Otters (2:13)