Populations Flashcards
What are the three phases for the usual pattern of growth?
- Slow growth- initially small number of individuals reproduce to slowly build up their numbers.
- A period of rapid growth where the ever increasing number of individuals continue to reproduce.
- A period when the population growth declines until its size remains more or less stable.
What are abiotic factors?
These are concerned with the non-living part of the environment
What are biotic factors?
These are concerned with the activities of living organisms.
What abiotic conditions influence the size of a population?
Temperature
Light
pH
Water and humidity
How does the abiotic factor temperature influence the size of a population?
Each species has a different optimum temperature.
Cold blooded- as temp falls below this enzymes work more slowly and so metabolic rate is reduced.
Above- potential denaturation.
Warm blooded- homestasis (maintaining temp)
However further from optimum = less energy spent on growth trying to maintain temp.
How does the abiotic factor light influence the size of a population?
Ultimate source of energy for ecosystems.
Rate of photosynthesis increases as light intensity increases.
Greater rate of photosynthesis increases growth rate.
How does the abiotic factor pH influence the size of a population?
Affects the action of enzymes.
Optimum levels.
How does the abiotic factor water and humidity influence the size of a population?
Where water is scarce populations are small (only well adapted).
Humidity affects transpiration rates in plants and the evaporation of water from the bodies of animals.
What is intraspecific competition?
Occurs when individuals of the SAME species compete with one another for resources such as food, water, breeding sites, etc.
What is interspecific competition?
Occurs when individuals of DIFFERENT species compete for resources such as food, light, water, etc.
Where populations of two species initially occupy the same niche, one will normally have a competitive advantage over the other.
What is predation?
Predation occurs when one organism if consumed by another.
Summarise the relationship between predators and their prey and its effect on population size.
Predators eat their prey, reducing its population.
Fewer prey- predators are in greater competition with each other for the prey that are left.
Predator population is reduced as some individuals are unable to obtain enough prey for their survival.
Fewer prey eaten.
Prey population increases.
Predator population increases.
What two major and relatively recent events that have led to an explosion in the human population.
The development of agriculture
The development of manufacturing and trade that created the industrial revolution.
Factors affecting the growth and size of the human population.
Birth rate and death rate.
Immigration and emigration.
Population growth =
(births + immigration) - (deaths + emigration)
