Lecture 15 Flashcards
What limits growth rates and population sizes?
Density Dependent factors
-Change in intensity as a function of population size
Density Independant Factors
-Alter birth and death rates irrespective of population size
What factors might regulate populations in a density independent fashion?
Usually abiotic
- Variation in weather patterns
- Catastrophic Events (Droughts, hurricanes, tornados, cold snaps, floods)
- Density dependent factors can interact with density independent factors to control population growth
Life History Characteristics
Life History traits govern fluctuations in populations size through time
- age when they 1st reproduce
- how often they reproduce
- number of offspring they have at a time
- amount of energy invested in each offspring
- average lifespan
Major Ideas from population growth
Exponential growth
-b and d (and therefore r) are constant, doubling time is also constant
Logistic Growth
-r varies; High when N is small, resources are abundant
-Low when N is near carrying capacity, resources scarce
Organisms vary in survival and reproduction traits (life history)
Maximum Sustainable Yield (MSY)
Highest rate at which a potentially renewable resource can be used indefinitely without reducing its available supply
-MSY=K/2