Population Dynamics and Conservation Bringing Back the Sea Otter Keystone species: Sea otter Sea...
Transcript of Population Dynamics and Conservation Bringing Back the Sea Otter Keystone species: Sea otter Sea...
Population Dynamics and Conservation
Bringing Back the Sea OtterKeystone 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 dispersionAge 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
ReproductivePostreproductive:
older than the maximum age of reproduction
Biotic Potential: Capacity for Growth
Intrinsic rate of increase (r)
Produce many offspring
Exponential Growth
Exponential Growth in Bacteria
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Time (Seconds)
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Reaching the Carrying Capacity (K)
Lack of food/ space in the petri dish?
S-shaped curve (logistic growth)
Amount of light, water, space, nutrients
Reaching Carrying Capacity on a Logistic Growth Chart
0
1000
2000
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1 3 5 7 9 11 13 15 17 19 21
Time (seconds)
# o
f In
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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 offspringTake care of
youthOffspring
usually lives to reproduce
SpecialistK-selected
Species
What limits growth?4 Variables
Births DeathsImmigrationEmigration
This occurs when (Births + Immigration) - (Deaths +
Emigration) = 0
ZERO POPULATION GROWTH
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 ResistanceAll 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
FloodsHurricanesEarthquakesLandslides
Density DependentCompetition ParasitismPredationDisease
1. Fragmentation and degradation2. Simplifying ecosystem3. Strengthening some populations of pest
species and bacteria (speeding up nat. selection)
4. Eliminating some predators5. Deliberately or accidentally introducing
new species
How have humans modified ecosystems?
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 = ConservationP = PreservationR = Restoration
(We are the world…we are the children…)