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• Entry Task:
– What is the difference between a biotic factor and an
abiotic factor?
• Learning Target:
– Understand the differences between abiotic/biotic and
the concept of a niche.
• Language Objective:
– Describe an ecosystem’s biotic and abiotic factors.
– Describe organism in terms of its habitat and niche.
• What is a biotic factor?
– Any biological influence on an organism.
– Includes all other living organisms in the ecological
• What is an abiotic factor?
– Any physical, non-living influence on an organism.
• Both determine survival and growth of an
organism as well as ecosystem productivity.
Recognizing Factors - QUIZ!!
• What is a habitat?
– Where an organism lives.
– Includes biotic and abiotic factors.
– Ex: for a frog, it could be a pond.
• What is a niche?
– Full range of conditions in which an organism
lives, both biological and physical, and how an
organism uses these conditions.
• No two species can share the same niche,
but niches can be similar.
What’s your niche?
• Make a personal place map.
– This will be a brief sketch in your notebook.
• What characteristics make it special to you?
– Draw 5 biotic factors and label
– Draw 5 abiotic factors and label
– Does anyone else like this place just the same way as
you do? Why is it special only to you?
• Entry Task:
– What are the six classifications of community
• Learning Target:
– Be able to recognize what type of interaction is
occurring in an ecological community.
• Language Objective:
– Describe interactions in an ecological community using
the proper terms associated with these interactions.
• What is competition?
– Both organisms want the same thing. Niches
develop as a way to reduce competition.
• Competitive Exclusion Principle:
– No two species can occupy the same exact
niche in the same habitat at the same time, so
they compete for resources and mates.
• What is predation?
– Interaction in which one organism captures and
feeds on another organism.
• What is a predator?
– The organism that feeds on another organism.
• What is the prey?
– The organism that gets fed upon by the
Which is which?
• What is symbiosis?
– Any relationship in which two species live
closely together.
– There are three main types of symbiosis
Symbiosis - Mutualism
• What is mutualism?
– Both organisms benefit.
– Ex: Each June in California's
hot San Joaquin Valley, paper
bags containing wasp and
pollen-bearing caprifigs are
stapled to limbs in Calimyrna
fig orchards.
– Ex: Bacteria in an organism’s
gut and on its skin usually
have a mutualistic relationship
with the organism.
Symbiosis - Commensalism
• What is commensalism?
– One member of the
relationship benefits, but
the other is neither helped
nor harmed.
– Ex: Barnacles can be seen
on the back of this gray
whale. This association
doesn’t hurt the whale,
but the barnacles get a
free ride.
Symbiosis - Parasitism
• What is parasitism?
– The relationship harms
one of the members.
– An organism that lives on
or in another organism
causes direct harm to this
– Ex: Leeches, harmful
bacteria, ticks, deer liver
“Community Interactions in the
High School” Skits
Groups of five
On the butcher paper at your station, include the following:
Definition of your assigned interaction (in your own words). See p.92
Example of your interaction in nature.
Create a short skit involving ALL group members of this interaction in
a high school setting.
1. Competition
2. Predation
3. Mutualism
4. Commensalism
5. Parasitism
Relationships in your Niche
• Describe three examples of community
interactions seen during today’s skits that
take place in your niche (personal place).
• These should be labeled and on the back of
your poster for “What’s Your Niche?”
• Entry Task:
– What is population density?
– What are the two types of population growth?
• Learning Target:
– Be able to recognize which type of population growth is
occurring and what might affect population size.
• Language Objective:
– Describe population changes using terms such as
population density, immigration, emigration, growth
(exponential and logistic), and carrying capacity.
• What is a population?
– A group of individuals in the same area
• What characterizes a population?
Geographic distribution, range (where they are)
Density (individuals per unit area)
Growth rate (how the size of a population changes)
Age structure (Chpt. 5-3)
Population Density
• There are 200 bull frogs living in a pond
that covers 4 square kilometers… What is
the density of the bull frog population?
– Population density = # individuals / Unit Area
• 200 bull frogs / 4 km2 = 50 bull frogs / km2
Human Population Densities
• Wenatchee: 451/square mile
• New York City: 27, 532/square mile
• Mumbai, India: 1,000,000/square mile
Population Growth
• What affects population size?
– # births
– # deaths
– # of individuals entering (immigration) or
leaving (emigration)
• When does growth occur?
– Birthrate > deathrate
– Immigration > emigration
Types of Population Growth
• Exponential growth
– J-shaped curve, constant rate of growth
– Occurs when there are unlimited resources and
no predation or disease. This are known as
ideal conditions.
Exponential Growth
Types of Population Growth
• Logistic Growth
– Natural populations do not exhibit exponential
growth all the time…
– Cases when growth slows or stops:
• As resources decrease
• Deathrate = birthrate
• Immigration = emigration
– Individuals a given environment can support =
Carrying capacity.
Logistic Growth
• Always some
fluctuation or slight
changes that make it
so a population is not
AT carrying capacity
all the time
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