Population Ecology Flashcards
Population
Group of individuals of a single species living in the same area
Population Ecology
Study of populations in relation to their environment - density, distribution, age, structure and size.
Why is density mostly impossible to determine
Complex interplay between emigration and immigration
Population Densite
Number of individuals per unit of area
Dispersion
Spacing of individuals in an environment
3 types of dispersion
- Clumped (number in area/group related to availability of resources)
- Uniform
- Randomly dispersed
What influences dispersion
Wind, pack hunting behaviour, pecking distance, nesting.
Why does dispersion matter
Resources (food, space, water, mates) are limited. How your arrange yourself in space influences the resources you have available to you.
Demography
Study of vital population statistics (death, reproductive rates, sex differences, life expectancy_
Life Table
Age specific summary of the survival pattern of a population
Semelparity
“Big bang” reproduction - reproduce once than die.
Iteroparity
Repeated reproduction
R strategy
Large number of offspring with little parental care, ensuring that at least some of them will grow and reproduce
K strategy
Small number of offspring and lavish resources on few individual - high survival rates.
Growth rate at a particular instant in time
Immigration and immigration are ignored. Growth = birth rate - death rate
Exponential Growth
Population increase under idealised conditions when rate of reproduction is at its maximum
Intrinsic rate of increase
Maximum rate of reproduction
Logistic model
Factors in the influence carrying capacity has on population numbers and growth
Why is exponential growth not a sustained pattern
Resources are limited. Carrying capacity (K) is te maximum population size the environment can support. Once K is reached, the rate of reproduction decreases.
What influences carrying capacity
Drought, unfavourable weather conditions, food availability, space, disease, introduction of species, climate change
When does a population have highest growth rates
Half carrying capacity
Logistic growth R value
Positive r number = more births than deaths and population will grow
Negative r number = more deaths than births and population will fall
Why is logistic equation important in real life
Fishing company trying to maximise stocks
Rat Free NZ - if your killing some but not all, the population growth will increase significantly
Density-dependent selection
selects for life history traits thast are sensitive to population density. (K = carrying capacity)
Density independent selection
goal of maximising reproduction. (r -independent of carrying capacity)
Competition & Density Dependence
In crowded populations, increasing population density intensifies intraspecific competition for resources
Boom and bust cycles
Population of one species is closely tied to another
