GEOG 201 - Lecture 10 (Equilibrium)
Prey population decreases if P>r/a (intrinsic rate of increase/) ~ equilibrium conditions
Use these as zero population growth isoclines ~ look at to know when predator populations
are not changing, increasing, decreasi
GEOG 201 - Lecture 9 (Mathematical models)
Population cycles can be caused by feedings relations, such as three-way interaction between
predators, herbivores, and plants
A specific effect of exploitation can be population cycle
Lemmings have huge populat
GEOG 201 - Lecture 8 (Preferences)
Circle=species, arrows = flow of energy
Indirect/exploitation competition - get energy from common resource
There are multiple levels of exploitative relationships
Over half of organisms obtain energy from feeding on ot
GEOG 201 - Lecture 7 (Models of Exclusion)
Using the Model to explain why competitive exclusion occurs
Looking at graph, competitive exclusion occurs when,
If you know alpha and beta, then you should know, depending on what the capacity are, if
they can c
GEOG 201 - Lecture 6 (Coexistence)
Competitive Exclusion: when isoclines do not cross, competitive exclusion results
Depending on which isocline is above the other, either species 1 or species 2 drives the other
to extinction
In (a), the final outcome of
GEOG 201 - Lecture 5 (Coexistence)
Coexistence when species compete for the same resources, we can use the mathematical
model to look their dynamics
If let dN/dt = 0 (equilibrium) not increasing or decreasing
When species 1 goes to 0, species 2 is K1/alp
GEOG 201 - Lecture 4 (Modelling)
Competition can be modelled using mathematical equations
Lotka-Volterra competition model : the first model of competition
Looks like logistic equation
Difference? alpha x N2 term N2 is population size of second species
P
GEOG 201 - Lecture 3 (Morphological Index)
Morphological index the larger the number, the more similar the two competitors are
morphologically; the more negative = more different (more different = higher growth rate)
The outcome of competition can be alt
GEOG 201 - Lecture 2 (Character Displacement)
Why show resource partitioning? Because of character displacement- results from when
natural selection influences the morphology of competing species
When species compete, they are being harmed. This is the f
GEOG 201 - Lecture 1 (Principles in Ecology)
Competitive exclusion principle: two species that use a limiting resource in the same way
cannot coexist
If the overall ecological requirement of a species (ecological niche) are very similar to those
of a sup
GEOG 102 - Lecture 10 (Competition in the Environment)
The distribution of larvae of the two species overlapped throughout the upper and middle
intertidal zone but the adult distribution did not overlap
Chthamalus were found only near the top of the inte
GEOG 102 - Lecture 9 (Competition in Closely-related species)
Example: When one species drives another to extinction
Competition strongest between very similar or closely-related species
Example: In experiments with rodents and ants that eat the same see
GEOG 102 - Lecture 8 (Types of Competition)
General features of competition
Exploitation competition species compete indirectly through their mutual effects on the
availability of a shared resource; competition occurs only because individuals reduce the
a
GEOG 102 - Lecture 7 (Plant Competition)
Experiments using two species of diatoms (single-celled algae that make cells walls of silica,
SiO2) were done by Tilman et al. (1981)
When each species was grown alone, they reached a carrying capacity and silica
GEOG 102 - Lecture 6 (Competition between species)
Logistic population growth (flatten out graph at carrying capacity because of densitydependence) reflects competition
Competition has been around for a long time (Struggle for existence, so you need to c
GEOG 102 - Environmental Stochasticity
Stochasticity = randomness
Demographic stochasticity - chance events related of the survival and
reproduction of individuals
Population-level birth and death rates are constant within a given year, but the actual
fa
GEOG 102 - Small Populations
Now. Switched from unlimited to limited food for adults
Fluctuations disappear = carrying capacity
Both adults and juveniles were limited
When limit food available to adults = fewer eggs
Juveniles more likely to turn into adul
GEOG 102 - Stable Limit cycle
The occurrence of fluctuations depend on the values of r and Tao
Robert May found that when r is small (between 0 and 0.368), no fluctuation results
At intermediate levels, (between 0.368 and 1.57), damped oscillations resul
GEOG 102 - Fluctuations in Population Sizes
In some populations, fluctuations occur as increases or decreases in abundance
from an overall mean value
Changes in phytoplankton
abundance in Lake Erie could reflect
changes in a wide range of
environment fac
GEOG 102 - Course Introduction (Review of GEOG 101)
Rate of change of population size over time = (dN/dt)
First part identical to exponential growth but (1-N/K) is added
What does the equation say?
When N is very small and
nowhere near carrying
capacity,
GEOG 101 - Lecture 10 (Logistic Growth and Carrying Capacity)
There are lots of things that stop population from growing that include densitydependent factors
The logistic equation incorporates limits to growth and shows how a population
may stabilize at
GEOG 101 - Lecture 9 (Factors affecting Population Size)
Population size can be determined 2 factors:
1. Density-independent does not depend on density of population (ex. fire,
tornado, environment event that happens regardless of population size)
Some s
GEOG 101 - Lecture 8 (Population Growths)
This predicts the size of an exponentially
growing population at any time t, if we have
an
estimate for r and know N(0), the initial
population size
The
graph to the right is both the geometric and
exponential gro
GEOG 101 - Lecture 7 (Geometric vs. Exponential Growth)
Lambda ~ Geometric growth rate; also known as the (per capita) finite rate of
increase
When lambda = 1, the population is stable (population is replacing itself and not
growing)
When lambda > 1, incr
GEOG 101 - Lecture 6 (Exponential Growth)
Example: Loggerhead sea turtles
Endangered (threatened by development on nesting sites and commercial
fishing nets)
What affects population growth and size?
1. Complex way of reproducing - go back to where born
GEOG 101 - Lecture 5 (Growth in Populations)
Population size growing but there is bouncing around early on
Eventually, the slope of line is same = stable age distribution
The growth rate (lambda) can be
calculated as the ratio of the population
size in ye
GEOG 101 - Lecture 4 (Life Table Data)
Life table data can be used to project the future age structure, size, and growth rate
of a population
A population can be characterized by its age structure the proportion of the
population in each age class
Age st
GEOG 101 - Lecture 3 (Survivorship)
Survivorship is high until 70s-80s
Survivorship varies among human populations
In Gambia lot of females die before 5 years old
Different survivorship at different months
Hungry season : not a lot of food to go around.
GEOG 101 - Lecture 2
Example: Data for a life table for the grass
Poa annua were collected by marking 843
naturally germinating seedlings and then
following their fates over time
3 thing important for life table:
1. Survival rate (SX): age-specific; chanc
GEOG 101 - Lecture 1
All organisms live in populations
All organisms produce offspring and interact with future generations
There are benefits (acquire resources, production, alter environment someway)
There are negatives (competing with other individual