Factors affecting population size Flashcards
What is the definition of population size?
The total number of organisms of one species in a habitat
What are some of the abiotic factors that act as a limiting factor to the population size of a species?
- light
- water
- space available
- temperature
- chemical composition
What are some of the factors that affect the human birth rate?
- economic conditions
- cultural and religious backgrounds
- social pressures and conditions
- birth control
- political factors
What are some of the factors that affect the human death rate?
- age profile
- life expectancy
- food supply
- safe drinking water and sanitation
- medical care
- natural disasters
- war
What is the definition of carrying capacity?
The maximum capacity of people the world can provide for
What is the definition of limiting factor?
Factors which limit the growth of the population size
Describe the 3 general stages of a population growth curve
- slow growth= a small number of individuals reproduce, with birth rate being higher then death rate
- Rapid growth= An ever-increasing number of individuals reproduce exponentially, so no constraints on the population size
- Stable state= reached carrying capacity, population declines until it remains stable with cyclic fluctuations. Birth rate is equal to death rate
What are the definitions of immigration and emigration?
- Immigration= The movement of individuals into an area
- Emigration=The movement of individuals away from an area
What is interspecific competition? Give an example
When organisms of different species compete with each other for the same resources e.g the red and grey squirrel compete for the same food and habitat in the k
Explain how the biotic factor, interspecific competition, can lower the population sizes of the competing species
The resources available to both populations are reduced as both are competing for and using it. This means both populations will be limited to a smaller amount of food, so they’ll have less energy for growth and reproduction, causing both population sizes to lower.
Explain how the biotic factor, interspecific competition, can affect the distribution of species
If two species are competing but one is better adapted to its surroundings, the less well adapted species is likely to be out competed, it won’t be able to exist alongside the better adapted species.
What is intraspecific competition?
When organisms of the same species compete with each other for the same resources.
Explain the affect infraspecific competition has on a species population, for example rabbits
- The population of the species increases when resources are plentiful, therefore increasing the amount of organisms competing for the same amount of space and food
- Eventually, resources become limiting, there isn’t enough for all the organisms to survive, causing the population to decline
- A smaller population then means there is less competition for space and food, which is better for growth and reproduction, causing it to grow once again
What is the definition of predation? Give an example
Where an organism (the predator) kills and eats another organism (the prey). The Lynx is the predator to the snow shoe hare
Explain the relationship of growth and decline of the population for the predator the lynx and the prey the snow shoe hare
- As the prey population increases, there’s more food for the predators, so the predator population also grows. lynx pop grows after show shoe hare pop has increases because more food available
- As the predator population increases, more prey is eaten, causing the prey population to begin to fall. Greater number of lynx eats lots of snowshoe hares, so their population falls. This is an example of negative feedback- the prey population is restored to a more stable size
- This means there is less food for the predators, so their population decreases (more negative feedback) and so on. Reduced snowshoe hare number means there is less food for the lynx so their population falls.
