Download Populations

Populations
Environmental
Science
NSC 22304
Ecosystem
• All living and non-living components in a
particular area
Biotic
•Plants
•Animals
•Microbes
Abiotic
•Soil
•Water
•Air
•Detritus
Ecosystem Subgroups
Community-All living organisms in an
ecosystem (i.e. biotic protion)
Population-All organisms of the
same species in an ecosystem
Example: All the
pickeral frogs in one
wetland
Population
All organisms of the same species in an
ecosystem
Pickeral frogs in two different wetlands
are 2 different populations though same
species.
Population Size
✦
✦
Number of individuals in a population
Symbolized by letter “N”
N=12
N=8
Do Activity 7 Populations if you
haven’t done so already.
Exponential “J” Growth Curve
• Population size increases proportional to
current size.
N
t
• Occurs when new species placed in
environment with lots of food and no predators.
Alaskan Island
128 sq miles
Yeast in Grape Juice
N
What do
you think
causes
crash?
Time
Yeast in Grape Juice
N
Lack of food
is good
hypothesis
but incorrect.
Time
Yeast in Grape Juice
N
Lack of
space is
good
hypothesis
but incorrect.
Time
Yeast in Grape Juice
Alcohol
which is their
waste
product kills
them.
N
Time
Invasive Species
•
•
•
•
Species put in an area by humans.
Much food.
Few if any predators
Grow exponentially.
Purple Loosestrife
• Plant brought to
US from Europe
for gardens
• Escaped to wild
• Invades
wetlands
• Outcompeting
native species.
Zebra Mussel
• Accidentally introduced to
Great Lakes in ship ballast
water.
• Has spread throughout
Mississippi River and
tributaries as well as other
river systems.
• Gets on boats, piers
• Clogs industrial pipes
Can you think of other invasive
species?
Logistic “S” Growth Curve
• Population increases to certain size and levels off.
• Occurs when predators or other factors limit growth
• K=Carrying Capacity - Maximum population size
environment can support indefinitely.
K
( )
dN
= rN K-N
dt
K
N
t
Biotic
Potential
Population “N”
Carrying Capacity
Environmental
Resistance
Exponential
Curve
Logistic
Curve
Time “t”
Environmental Resistance
• Factors that inhibit population growth
• Includes:
•
•
•
•
Predators
Disease or Parasites
Competitors
Adverse Weather - flood, drought, fire,
etc.
• Amount of resources - food, space,
water, etc.
Biotic Potential
• Biological ability of population to grow.
• Factors affecting potential:
•
•
•
•
•
•
Life span
Age of first reproduction
Number of offspring per reproduction
Number of times individuals reproduce
Ability to spread
Ability to withstand adverse conditions
Population Balance
N
Biotic Potential
Environmental Resistance