Chapter 17 Comparing Multiple Population Means: One-factor ANOVA.
A factor that has a greater effect on population as the Note Sheets… · A factor that has a...
Transcript of A factor that has a greater effect on population as the Note Sheets… · A factor that has a...
A factor that has a greater effect on population as the density increases or decreases.
Factors are typically biotic (living)
Ex: The common loon, a bird found in Ontario, nest on a lakeshore, but rarely shares a lake with another pair of loons.
• Density-‐dependent: the population is limited by the number of nesting lakes available
• Ex: The population of pet mice in a cage stops increasing even though enough food is present to support a larger population.
• Density-‐dependent: the size of the population has stopped growth due to the number of
organisms being limited by nesting sites (or similar)
" Mangrove trees are often seen in the Florida everglades, their roots alternately exposed to the air, or submerged in water. Few tree species can survive such varied exposure. Mangroves can grow outside of the swamp, but rarely do. What are the ecological reasons for the unusual habitat of the mangrove?
" One animal kills and eats another
" Humans raise cattle for food
" Predation is beneficial to one species, but usually lethal to the other
" Controls the number of a population of prey
" Population too small and cannot survive due to difficulty finding a mate (population density is too low)
" Neanderthals may have died out when their birth rate became too low to offset their death rate.
" The minimum viable pop. size consists of enough individuals so that the population can cope with variations in natality and mortality as well as environmental change or disasters.
" A population is considered at risk of becoming extinct when its number falls below the minimum viable population size
Note:
When a population is small enough to be far below its carrying capacity, density dependent factors have little effect and the population growth is rapid.
Eventually, the population reaches a density at which these factors start to have an effect; after this point the population growth slows, and it eventually stops when the carrying capacity is reached.
" Factors that influence population regulation regardless of population density
" Factors tend to be abiotic (non-‐living factors)
2. Insecticide application – biomagnification (concentrates up the food chain)
3. Floods, Droughts
4. Forest fires, hurricanes, tornadoes
" An essential resource that is in shortest supply or unavailable
" Limiting factors prevent populations from achieving their biotic potential
" è Determines the carrying capacity " ex. light, space, water or nutrients
Water is the è limiting factor
Practice Questions: pg 675 Q’s1-‐4