4. Populations Flashcards
Name biotic factors
- Temperature
- Light
- pH
- Water and Humidity
What is predation
An interspecific relationship where one organism (predator) feeds on another organism (prey)
What two factors caused the human population to rapidly increase?
- The development of agriculture
- The development of manufacturing and trade
Population growth rate =
(Population change during the time period)/(population at the start of the time period) x 100
Birth Rate =
(Number of births per year / total population of the same year) x 1000
Death Rate =
(Number of deaths per year / total population in the same year) x 1000
Describe the age population pyramid of a stable population.
The birth and death rate are in balance so there is no increase or decrease in population size. (The pyramid is widest at the base, and there is no curve)
What causes population size to vary?
- The effect of abiotic factors
- Interactions between organisms, such as interspecific competition and intraspecific competition or predation
Describe an increasing population
There a is a high birth rate, giving a wider base to the pyramid, and a narrower apex to the pyramid (The pyramid is curved)
Describe a decreasing population
There is a lower birth rate (narrower base) and a lower death rate leading to more elderly people (a wider apex of the pyramid). The base of the pyramid is not the widest point.
What is a survival rate curve?
It plots the number of people still alive at a certain time, typically as a percentage
How to calculate life expectancy from a survival curve
The age at which 50% of the individuals in a particular population are still alive.
What is succession
The changes in species that occupy a particular area
What happens in different stages of succession.
Certain species may be recognised which change the environment so that I becomes more suitable for other species.
What do the changes in abiotic features result in?
A less hostile environment and changing biodiversity
