Explores how biotic and abiotic factors influence the abundance, dispersion, and age structure of populations
Population Density Factors
Biotic and abiotic factors affect population density, dispersion, and demographics
Dispersion
The pattern of spacing among individuals within the boundaries of the population
Mark-Recapture Method
Capture, tag, and release sample of individuals in a population.(s) Capture second sample of individuals(n) and note how many are marked. (x) N=population size
N= sn/x
Emigration
The movement of individuals out of a population
Patterns of Dispersion
Most common pattern is CLUMPED, this is when individuals aggregate in patches.
Benefits of clumped
resource availability
Mating Behavior
Group defense against predators
Uniform dispersion
Individuals are evenly distributed. Influenced by territoriality, the defense of other individuals.
Random Dispersion
The position of individual is independent of other individuals
Demography
Study of these vital statistics of a population and how they change over time
cohort
group of individuals of the same age
Survivorship curves
Graphic way of representing the data in a life table
Survivorship Curves
Type 1: low death rates during early & middle life and an increase in death rates among older age groups
Type 2: A constantdeathrate over the organism's life span
Type 3: High death rates for the young and a lowerdeathrate for survivors
Reproductive Rates
Reproductive output for sexual organisms is measured as the average number of femaleoffspring produced by the females in an age group
population growth rate equation
N/t=B−D
N is the change in population size, t is the timeinterval, B is the number of births, and D is the number of deaths
Exponential Population growth
Population increase under idealized conditions
Carrying Capacity
(K) is the maximum population size the environment can support
Logistic model
describes how a population grows more slowly as it nears its carryingcapacity
The logistic Model and real populations
S-shaped curve. These organisms are grown in a constant environment lackingpredators and competitors
Organisms life history
The age at first reproduction (maturity)
How often the organism reproduces
How many offspring reproduced
Semelparity
Reproduce one and die
Iteroparity
repeated reproduction, produce offspring repeatedly
Density-independent
populations, birth rate, and death rate don't change with population density
Density-dependent
populations, birth rates fall, and death increase with rising population density