Population ecology

what is demographic dividend?

economic growth as a result of a change in the population structure i.e. low dependency ratio

what are population growth dynamics?

study of how and why population size and structures change over time

what are the three scenarios of population balance?

optimum population

overpopulation

underpopulation

what does optimum population mean?

all resources are used to give the highest economic return per person and therefore the highest standard of living

what two things can lead to a higher ooptimum population?

low dependency ratio

improvements in technology

what is environmental resistance?

group of factors that control mortality rates

what is environmental resistance also known as?

limiting factors

what does it mean for a limiting factor to be ‘density independent’?

not influenced by the population size and density e.g. natural hazards will increase the death rate no matter what the population size is

example of density dependent limiting factor

food supply

what is biotic potential?

natural reproductive potential of the species

what happens when biotic potential > environmental resistance?

rapid population growth during log phase

what does underpopulation mean?

too few people to use resources efficiently for a given level of technology

what is ecological footprint?

measure of the demand placed by humans on Earth’s natural ecosystems

what unit is ecological footprint in?

gha (global hectares) per person

what is overshoot?

point when the population and its consumption of resources exceed the long-term carrying capacity

what is total productive bio-capacity?

all food, water and energy resources produced by the Earth’s natural systems annually to sustain us

how does Rees calculate carrying capacity?

(total productive bio-capacity) / (total population)

what does a gha represent?

unit of measurement representing the average productivity of all biologically productive areas on earth in a given year

what is the USA’s avg ecological footprint?

8.1 gha per person

what is Zambia’s avg ecological footprint?

less than 1 gha per person

how much ecological footprint does each person have available?

2 gha

how long does it take for Earth to replenish what we consume in a year?

1.6 years

what is Earth Overshoot Day?

the day it is thought we have used the productive bio-capacity

when was Earth Overshoot Day in 2000?

1st Nov

when was Earth Overshoot Day in 2014?

19th Aug

what is the logistic model of population growth?

as population size increases, the rate of increase declines as more environmental resistance is encountered

what shape is the curve of the logistic model?

sigmoidal - S