Download Eco Notes 2 Population Dynamics

Ecological Population
Dynamics
Biotic potential
• The maximum number of offspring an
organism can produce is its biotic
potential.
• What keeps organisms from reaching
their full biotic potential?
• Environmental limits (not enough food,
water, shelter or things like disease,
predation). These limits are called
environmental resistance.
Population Growth Models
Exponential model
• idealized
• Called “r populations”
(J-curve)
Logistic model
• realized
• Called “K populations”
(S-curve)
Which one happens most
often? Why?
Strategies to increase biotic
potential
• r-selected
•
•
•
•
•
(opportunistic)
Short maturation &
lifespan
Many (smaller)
offspring
No/little parental care
High death rate
EX:?
• K-selected
(equilibrial)
• Long maturation &
lifespan
• Few (larger)offspring;
• Extensive parental care
• Low death rate
• EX:?
Population limiting factorsEnvironmental resistance!
• Density-dependent
factors: • limited food water,
shelter •predation • disease
• Density-independent
factors •weather/climate
• These factors lead to K*
• (*K=The max number of
individuals an area can
sustain/Carrying capacity)
• Biotic potential vs
Environmental resistance!
(All life must deal with this)
• Leads to adaptation
More ways to increase success is to
partake in Symbiosis. (2 unrelated
organisms living close together.)
Mutualism
+/+ both species benefit
Commensalism
+/o one species benefits, the other is unaffected
Parasitism
+/- one species benefits, the other is harmed
Neutralism
o/o Neither organism benefits or is hurt
Types of competition:
• Intra-specific competition: occurs
among organisms belonging to the
same species.
• Inter-specific competition: occurs
between organisms from different
species (predator-prey)
Competition reduction
• Resource partitioning~
species consume slightly
different foods or use other
resources in slightly different
ways (Develop niches)
• Character displacement~
sympatric species tend to
diverge in those
characteristics that overlap
Ex: Anolis lizard sp. perching sites in
Ex: Darwin’s finch beak size on the
the Dominican Republic
Galapagos Islands
Predator/ Prey relationshipsspecial competition
5 Types of specific coloration
adaptations:
• Aposematic coloration – Stay away color
• Batesian mimicry – copy cat, only 1 bad
• Mullerian mimicry – 2 poisonous resemble
one another
• Camouflage – blend in
• Disruptive coloring – obscures size or shape
of organisms body.
All organisms characteristics
and behaviors lead to
increased survival.
We can measure those
outcomes….
Survivorship curve – plot of numbers that
still alive at each age
• Type 1 –Death
more likely at old
age
Type 2 –Death
equally likely at
all ages
• Type 3 –Death
more likely at
young age
Where would you place k selected and r
selected populations?
Big Changes in the system
• Primary
succession- going
from nothing (no
soil)to pioneering
community to
climax
community.
• Why would there
be nothing???
– Melting glaciers
– Volcanic
eruptions
– Landslides
– Strip mines
• Secondary Succession - Re-establish an
ecosystem after a disturbance
• What could be a possible disturbance?
– Flood
– Fire
Geographic dispersion of a
population shows how individuals
in a population are spaced.
• Population
dispersion refers
to how a
population is
spread in an
area. (Density)
Clumped
dispersion
Uniform
dispersion
Random
dispersion
Random Sampling
• Take the area you are
analyzing. Divide it into
equal quadrants.
• Randomly select a specific
number of subdivided
quadrants, count all
organisms in those areas.
• Add up all organisms
counted, divide by # of
quadrants than X by total
quadrants.
• 8/4=2 X16=32
• Actual = 26
• PROBLEMS?
Capture mark-recapture
(Lincoln-Petersen index)
• In a given area, capture a specific number of
organisms, mark them and release them back into
the wild
• Over a set amount of time, recapture a preset
number of organisms and keep track of how many
have already been captured. (They have marks)
• Use math to estimate total population in an area.
• Problems?