Transcript Ecology - Bev Facey Community High

Ecology
Biology 30
Ecology
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Study of Ecosystems
Abiotic & Biotic factors interacting
Biotic Factors include populations & communities
Population
•Same species
•Same place
•Same time
Community
•Groups of pops
interacting
Same species: Same place: Same time!
Can you explain the difference between
a population and a community?
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The definition for a population?
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The definition for a community?
Biotic and Abiotic Factors?
Abiotic factors are
the non-living
components of an
ecosystem
Biotic factors are
the living
components of an
ecosystem
Can you tell me…
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The difference between abiotic and biotic
factors in an ecosystem?
An example of an abiotic factor?
An example of a biotic factor?
Ecosystem Community
or Population?
Community
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Why is the picture in the previous slide an example
of a community and not an example of a
population?
Populations
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Variables we will consider:
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Geographic Range
Habitat
Ecological Niche
Population Distribution
Population Size
Population Density
Population Growth Rate and Patterns
Geographic Range
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area where animal has been seen
Fire Ant Range
Geographic range can change over time
due to abiotic factors.
Range Changes in Moose Populations
How has the geographic range of moose
changed since the 1870’s??
Habitat
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area where the population lives
where environmental conditions are best
for survival
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How does an organism’s geographic range
differ from its habitat?
Ecological Niche
Role of the species in the community
 Includes ALL biotic and abiotic factors a
species needs to survive
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Each group has a different role to
minimize competition
Populations co-exist only if each group occupies a different niche
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Explain the meaning of the term ecological niche.
Population Distribution
Uniform
Clumped
Population Distribution
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Determined largely by habitat preference
Divided into three patterns:
1. Clumped - individuals grouped in patches due to
certain environmental factors (e.x. trees clump on south
slopes of river valleys b/c less direct sunlight and
sturdier soils)
2.
Random
- not very common
- biotic and abiotic factors have little effect
3.
Uniform
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competition among individuals for resources
results in regular spacing
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What is the difference between clumped, random
and uniform population distribution?
What factors are responsible for creating clumped,
random and uniform population distributions?
Population Size
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Number of organisms of same type in
same place, at same time
There are 2000 students at Centre High
during the 2004/5 school year.
Can be determined by exact count or
estimation!!
Population Density
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Describes number of organisms in a defined
area
eg. Snow geese at Beaver Hills =
# of geese per hectare
Density (D) calculated by dividing total
number (N) by amount of area occupied (A)
by the population
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What is the difference between population size and
population density?
Density Example
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If 200 lemmings are living in a 25 hectare (ha)
area of tundra, what is the population density
of this area?
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Use the formula D = N/A
Growth Rate
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After finding the population density, we
can find the rate of change over time
Change in number
Rate of growth
Change in time
Density Change example
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In 1993, the mouse population in my
backyard was 50 mice/acre. After three
years, various control measures had been in
place, and the population dropped to 10
mice/acre. Calculate the rate of density
change.
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When arriving at their summer cabin, the Smiths
discovered 10,000 cockroaches roaming throughout
their 1000 m2 cabin. After 1 week, the exterminators
were able to control the situation and reduced the
cockroach population to 10 per 1000 m2. Calculate the
rate of density change.
Population Growth
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Determined by four
factors:
Natality
 Mortality
 Immigration
 Emmigration
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Population Growth
Also known
as per capita
growth rate
Calculation
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Using this table, calculate CGR for
Sandhill cranes:
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Puffins are small marine birds
found off the coast of Atlantic
Canada. Calculate the population
growth rate of a puffin colony
based on the following population
in 1999.
Original population = 200 000
Natality = 15 000
Mortality = 10 000
Immigration = 175 000
Emigration = 160 000
Density Problem
Calculate the population density of shrews
per m2, if an average of 7.8 shrews are
found in an area 14 m wide by 20 m.
CGR Calculation
Calculate the per capita growth rate of a mouse
population if the original population size is 34 and
over a period of a week, 5 die, 8 are born, 12
immigrate into and 7 emigrate out of the area.
Dynamic Equilibrium
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Present in mature ecosystems
Characterized by long term balance
Pops remain relatively stable over time
Great biodiversity = stability
Can be compared with homeostasis
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Define dynamic equilibrium.
2 population types:
1. Open populations:
 immigration & emigration occurs
2. Closed populations:
 Density changes are result of natality
and mortality only
 No immigration or emigration
 eg. Game preserves
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What is the difference between open and
closed populations?
Growth Curve
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Graph showing changes in a population over
time.
X = time (independent or manipulated
variable)
Y = density or # of organisms (dependent or
responding variable)
Exponential Pop Growth
Growth Curve for Closed
System
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4 phases:
1. Lag phase…slow…not enough
reproducing organisms
2. Growth phase….exponential increase
3. Stationary phase….natality= mortality
4. Death phase…decline
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Not always present
Bacterial Growth Curve
Closed population
4 distinct phases
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Draw a growth curve for a closed population.
Label and define the four stages of this curve.
Growth Curve for Open Systems
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When a limiting factor is introduced to a
population, curve results in an “S” shape
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As organisms respond to increased nutrients,
natality increases.
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Typical of an organism placed in a new environment
Equilibrium is established again and curve levels off
New carrying capacity (max. # of individuals
environment can support)
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Define carrying capacity.
When does a population growth curve of an
open system show an “S shape”?
Population Growth Curves
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Click on the link above
Read the instructions and hit the “run applet” button
Set the carrying capacity to 1000
Set the birth rate to 1.5
Hit RUN
View the graph and draw this in your notes
Have you simulated an open or a closed population?
Change the parameters and try it again!
Population Curves
Human Population Growth
Population Curves
Population Curves
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How could you describe the population growth
of humans in the past 500 years?
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Hint: one word that begins with an ‘e’
Population Explosion & Crashes
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Describe the bottleneck effect.
Boom and Bust Cycles
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What trends do you see in the population curve
for Soay Sheep that give its characteristic
shape of “boom and bust”?
Survivorship Curves
Population Curves
Population Curves
Population Histograms
Wide base…fast growth
Narrow base….decline
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What information is given in a population
histogram?
What shape would a histogram look like if it
were representing an declining population? A
stabilized population? A young population?
More Histograms
What are these graphs showing?
1. Which country demonstrates
a very high reproductive
rate?
2. Which country represents a
stabilized population?
Show Age Structure
of Pop
Histograms
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What do each of the histograms on slides 63 to
64 tell you?
What trends do you see in the population
curves on slides 63 to 64?
Biotic Potential
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Max. # of offspring produced in ideal
conditions
Regulated by four factors:
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offspring - max #/birth
survival capacity – chance that offspring
will reach reproductive age
procreation - # times/year organism
reproduces
maturity - age when reproduction begins
Environmental Resistance
All factors that limit pop.
growth
 Can be biotic or abiotic
 Examples include…….
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Food, water, space, disease, predation, natural
disasters, availability of mates, etc
Environmental Resistance
In a
fresh
water
habitat
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Define biotic potential and environmental
resistance. Give an example for environmental
resistance.
Limiting Factors
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Affect population size!
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flood, fire, extreme cold, disease, starvation,
predation
Law of the minimum
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various substances are required for growth.
the one with the lowest concentration will limit
growth ( known as limiting factor)
Limiting Factors can be:
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Density Independent:
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affecting pop regardless of # of individuals
flood, fire, extreme cold, other abiotic factors
Density Dependent:
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affecting pop & dependent on pop size
disease, starvation, predation
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State the law of the minimum.
Define limiting factors.
What are some examples of limiting factors?
Name the
Density Dependent Factor!
Pops can also be r or K Selected
K - selected
r - selected
High
Reproductive
Rate
Low
Reproductive
Rate
Almost at
Carrying
Capacity
K- selected Populations
r- selected Populations
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Differentiate between r and K-strategies. Give
2 examples of the types of organisms that use
each of these strategies.