3.2.4.5 Principles of Population Ecology Flashcards
biotic potential
in population ecology, the natural reproductive potential of the species
environmental resistance
explain mortality rates controlled by environmental factors that prevent survival (disease or shortage of food)
biosphere
biological component of earth systems
carrying capacity
maximum population size that an area or environment can sustain indefinitely
ecological footprint
a measure of the demand placed by humans on earths natural ecosystems
overshoot
referring to a point when the population and its associated consumption of resources exceed the long-term carrying capacity of its environment
total productive bio-capacity
all the food, water and energy resources produced by the earths natural systems annually to sustain us
Population ecology
Population growth determined by BR and DR
BR are controlled by
The reproductive or biotic potential of the species - a rate that evolves over time and related to survival rates of the young
DR controlled by
Environmental factors that limit survival
Density independent environmental factors
Not influenced by population size and density e.g. Natural hazards
Density dependent environmental factors
influenced by population size and density e.g. Food supply and disease
When the biotic potential is greater than the environmental resistance…
The population grows
The population has overcome environmental resistance so…
The population has grown rapidly
World population stable for most of history due to
High BR and DR (famine and disease)
If population outstrips resources
Overpopulation occurs
When resources are greater than demands
Underpopulation occurs
Overpopulation
When there are too many people in the area relative to the available resources putting pressure on those resources
Underpopulation
When there are too few people to use the resources efficiently for a given level of technology
one global hectare (gha)
represents the average productivity of all biologically productive areas (cropland/forests/fishing grounds etc) on earth in a given year
global hectares per person
amount of global hectares needed by each person to provide for their consumption of resources
carrying capacity depends on
the average lifestyle in different parts of the world
countries with a higher demanding lifestyle will have
a lower carrying capacity- more developed countries
how is carrying capacity calculated
taking earth’s total productive bio-capacity and dividing by the total population which is how many global hectares are available per person on earth
reason for greatest growth in ecological footprint
carbon (doubled 1960-2010)
negative impacts of ecological footprint
climate change, more landed needed for settlement, industry and transport, extinct species, reduction of crops and soil quality, depletion of fish stocks, degradation of ecosystems
what does Rees state
we are already in a state of overshoot reaching ‘overshoot day’ in 2014 so now in ecological debt
what the logistic model shows
the rate of increase of global scale population growth declines as more environmental resistance or limiting factors are encountered (food/water) reaching a state of equilibrium
what is the population, resources and pollution model (PRP)
how all organisms interact with their environment (see pg 193 revision guide)
positive feedback on the PRP model
where one activity increases another moving it away from equilibrium to an unstable state
negative feedback on the PRP model
where one activity reduces another thereby achieving equilibrium
cross-media contamination
pollution that can contaminate many areas (acid rain affects forests/rivers/lakes)
