Population Growth and Regulation Flashcards
Population
Group of individuals of the same species
Population Growth Rate
The number of new individuals produced per unit of time minus the number that die
Population ecology is…
Conservation of threatened species. Control of over abundant pest and invasive species. Responsible management of invasive population
Log b^y=d same thing as
b^d=y
Log functions reverse
exponential functions
E (Eulers Number)
2.718. Exponential function with e. Mathematically convenient in population dynamics
The natural log
e and In
(Loge)^y can also be said as
(In(^y
Nile Perch Population Growth
Population grew exponentially and contributed to extinction or near extinction of more than 200 species.
Exponential Growth Model
Nt=Noe^rt
-Population growth under “ideal” conditions. -Relative growth rate is constant.
-r is a constant rate specific to the population
-the observed rate changes
-highest observed growth rate
The actual observed rate of a populations growth at any specific point in time
DN/dt=rN
Intrinsic Growth Rate (R)
Highest possible per capita growth rate for a population. “Instantaneous growth rate”
R=Births(b)-Deaths(d)=Immigration(I)-Emmigration(E) or in shorter terms…
R=b-d
if b>d then…
positive growting population
Geometric Growth Model
Nt=N0lambda^t
-like the exponential growth model but discrete
-compares population size at regular time intervals
Lambda
Discrete population growth rate
Lambda=
Nt/Nt-1
Geometric growth model accounts for
Seasonal births, and breeding periods common in nature
t2 =
The time required for a population to double in size
For continuous growth (exponential), t2 is
loge^2/r
For discrete growth (geometric) t2 is
loge2/logelambda
Exponential and geometric models are
density independent (assumes constant birth and death rates)
Indefinite growth is not possible because of
resource limitation, epidemics and other natural enemies, environmental change and natural disasters
Limits to population growth
Density independent factors and density dependent factors
Density independent factors
Not related to populations density. Often abiotic (floods temperature)
Density dependent factors
Related to density. Often biotic (disease, competition for food and space)
Negative Density Dependance
High population density leads to negative population growth from competition (intraspecific) and disease. Birth rates increase death rates decrease
Positive Density Dependance
Low population density. Low even negative population growth. Inability to find mates or forage successfully
Population Regulation
Often involves positive and negative density dependence. Increased densities with abundant resources. Above some density resources become limiting
Negative Density Dependence depends on a
carrying capacity (K)
Carrying Capacity (K)
the maximum population supported by the environment
Above K means
low reproduction and survival cause negative population. Often treated as a constant but can vary with environmental conditions. Often treated as constant but can vary in environmental conditions.
Logistic model of population growth
Describes slowing growth of population at high densities. Represented by rate of growth with carrying capacity factors added to it. dN/dt=rN(1-N/K) (r is still intrinsic rate of increase)
Inflection Point
Maximum observed growth rate (dN/dt) when N=k/2
Populations can overshoot K sometimes resulting in
extinction
Density Independent Limitation
Birth and death rates unaffected by population size. Does not mean infinite growth. (not be sustainable). Many factors can prevent populations from ever reaching K (disturbance, climate, fire, specialist predation)
