Population ecology:
Study of groups within a species that interact mostly with each other
Population:
Group of individuals of a species who interact regularly
Population density:
How many individuals are interacting in a given area
Factors determining density:
Birth/immigration increases the population density Death/emigration decreases the population density
Dispersion:
The geographic arrangement of individuals in a population
Population growth:
The increase in population size
Factors affecting population growth
Fecundity:
How many offspring an individual can have in a lifetime
Carrying capacity:
Number of individuals that a habitat can sustain
Limiting factors for population growth:
They are broadly grouped into density dependent and density independent
Density dependent factors:
Density dependent factors limit growth because of the stress on the environment due to number of individuals
Density dependent factor start to kick in when the carrying capacity is reached
They include:
Food, water, number of predators, space, disease, number of mates
Density independent factors:
Density independent factors are due to things other than number of individuals
They cause a change in a crucial aspect in the population's lifestyle
They include:
Natural disasters, human made disasters, temperature and other environmental factors
Per capita growth rate:
Rate of population growth per individual
It is calculated as follows,
r = (Births - Deaths)/N = (M - N)/N
Births is number of births in a given time
Deaths is number of deaths in a given time
N is size of population at the start
N is size of population at the end
r is the per capita rate of growth
Types of population growth:
Exponential growth:
The population grows at a rate proportional to its size
In absence of limiting factors, population grows exponentially
Logistic growth:
Population growth is limited to the carrying capacity
The limiting factors are almost always density dependent factors