Population Ecology

Question 1

To calculate the change in a population

Answer 1

N = (B + I) - (D + E)

Question 2

Carrying Capacity

Answer 2

The size of the population that can be supported indefinitely on the available resources and services of that ecosystem. ie. It is the maximum population size of the species that the environment can sustain indefinitely, given available resources

Question 3

Limiting factors

Answer 3

Resources that a population requires but which if present in small quantities, negatively impacts on population growth (creates unfavourable conditions for the population). Limiting Factors can be density dependent or density independent.

Question 4

Density-independent limiting factors

Answer 4

Affect the population size regardless of the density / size of the population. Two major categories of these:

i) regular abiotic conditions eg. water availability, temperature, light levels, salinity that impact on survival.

ii) irregular disturbances eg. flood, fire, drought

Question 5

Density-dependent limiting factors

Answer 5

Affects on population size are determined by the size of the population (effects increase as population increases)

Major examples include: competition for resources (eg interspecific & intraspecific competition), predation, disease, overcrowding effects.

Question 6

J shaped population curves

Answer 6

Depict an exponential growth mode and are typical of opportunistic density independent species such as insects or weeds. These organisms typically are short lived, have short generation times and give rise to a large number of offspring rapidly (r strategists) and will continue to exhibit a population explosion while resources are plentiful / unlimited (growth may be stopped suddenly by a limiting factor causing a population crash)

Question 7

S shaped population curves

Answer 7

Depict a logistic growth mode and are typical of density dependent species. These organisms typically are relatively long lived, have long generation times and give rise to only a few offspring at a time (k strategists ). Population growth increases slowly, then exponentially until it levels off as environmental resistance (density- dependant factors) limits growth and carrying capacity (a stable population level) is reached.

Question 8

The Lincoln Index

Answer 8

Is a measure used to estimate the size of a population where random samples of the population are captured, marked and released to mingle back with the general population for a period of time before some are recaptured.

Question 9

Lincoln Index Formula

Answer 9

N = (M x n)/m

N = (number of individuals caught, marked and released initially x number of individuals caught on the second same)/ number recaptured that were marked