Transcript Population Dynamics and Conservation

Population Dynamics and Conservation
Bringing Back the Sea Otter
 Keystone species:
Sea otter
Sea urchin
Kelp beds
Ode to the Sea Otters…
Before
 1 million sea otters lived in
the pacific
 Hunters believed to have
killed all the sea otters in the
early 1900’s
After
 1938: 300 sea otters were
counted
 After the U.S. Endangered
species act and the marine
mammal protection act, now
about 2,300 sea otters swim
the pacific
Population Dynamics Depend On:
 Size: number of individuals in a population at a
given time
 Density: number of individuals of a population in
a certain location at a given time
 Population dispersion
 Age distribution
Population Dispersion:
Clumping
 Members in clusters or
groups
 Food resources found in
clumps
 Source of protection
 Helpful during mating
season
Uniform Dispersion
 Individuals of the same species compete for resources that are
scarce and spread evenly.
 Cresote bush release toxins that prevent seeds from growing
near it.
Random Dispersion
 Unpredictable pattern
 Resources and conditions
are uniform in the habitat
 Rare in nature
Age Structure
 Prereproductive:
younger than sexual
maturity
 Reproductive
 Postreproductive: older
than the maximum age of
reproduction
Biotic Potential:
Capacity for Growth
 Intrinsic rate of
# of Individuals
increase (r)
 Produce many
offspring
 Exponential Growth
Exponential Growth in Bacteria
4500
4000
3500
3000
2500
2000
1500
1000
500
0
1 2 3 4 5 6 7 8 9 10 11 12
Tim e (Seconds)
Reaching the Carrying Capacity (K)
 Lack of food/
Reaching Carrying Capacity on a
Logistic Growth Chart
5000
4000
3000
2000
1000
Time (seconds)
21
19
17
15
13
11
9
7
5
3
0
1
# of Individuals
space in the petri
dish?
 S-shaped curve
(logistic growth)
 Amount of light,
water, space,
nutrients
Which strategy would you use?
 Many offspring at
young age
 Most offspring die
before reproducing
 Generalist specie
 R-selected
Species
And what about these organisms?
 Few offspring
 Take care of youth
 Offspring usually
lives to reproduce
 Specialist
 K-selected
Species
What limits growth?
 4 Variables
 Births
 Deaths
 Immigration
 Emigration
ZERO POPULATION GROWTH
This occurs when
(Births + Immigration) - (Deaths + Emigration) =
0
MVP…
 Q: When do you stop using the same resource (ie. fish) for
food?
 A: You stop before reaching the resource’s minimum
viable population (MVP) It is the min. pop. size needed
for breeding
Environmental Resistance
 All factors working together to limit the growth of a
population
 Biotic Potential + Envir. Resistance determine a population’s
Carrying Capacity
Density Independent vs. Density
Dependent Population Control
Density Independent
 Floods
 Hurricanes
 Earthquakes
 Landslides
Density Dependent
 Competition
 Parasitism
 Predation
 Disease
How have humans modified
ecosystems?
1. Fragmentation and degradation
2. Simplifying ecosystem
3. Strengthening some populations of pest species and bacteria
(speeding up nat. selection)
4. Eliminating some predators
5. Deliberately or accidentally introducing new species
6. Overharvesting potential renewable resources
7. Interfering with normal chemical cycling and energy flow
(CFCs, Ozone, etc.)
What do we do about it???
GLOBAL CPR
C = Conservation
P = Preservation
R = Restoration
(We are the world…we are the children…)