Reproductive Strategies and Population Fluctuations Not all species reach a stable carrying capacit Species can be broadly lumped into two categories K- strategists R-strategists
Reproductive Strategies and Population Fluctuations • Not all species reach a stable carrying capacity. • Species can be broadly lumped into two categories: – K- strategists – R-strategists
K- Strategists Characteristics arge organisms-long -lived Produce few offspring Provide substantial parental care Populations typically stabilize at a carrying capacity Reproductive strategy is to invest in a few, quality offspring Limited by density-dependent population controls Factors that become more severe as the population grows in size. (Diseases) Examples Deer-Lions -Humans
K - Strategists • Characteristics – Large organisms - long-lived. – Produce few offspring. – Provide substantial parental care. – Populations typically stabilize at a carrying capacity. – Reproductive strategy is to invest in a few, quality offspring. – Limited by density - dependent population controls. Factors that become more severe as the population grows in size. (Diseases) • Examples – Deer - Lions - Humans
R-Strategists Characteristics Small organisms- Short-lived Produce many offspring Little if any parental care Usually do not reach carrying capacity(boom-bust cycles) Reproductive strategy is to produce large numbers of offspring to overcome high mortality Limited by density-independent population controls , Populations size is irrelevant to the limiting factor (weather conditions) EXamples Grasshoppers-Gypsy Moths-Mice
R - Strategists • Characteristics – Small organisms - Short-lived. – Produce many offspring. – Little if any parental care. – Usually do not reach carrying capacity (boom-bust cycles). – Reproductive strategy is to produce large numbers of offspring to overcome high mortality. – Limited by density-independent population controls. Populations size is irrelevant to the limiting factor (weather conditions). • Examples – Grasshoppers - Gypsy Moths - Mice
Human Population Growth Major reason for increasing human population growth rate is an increase in medical care, and a consequential decrease in death rates Doubling Time of a population(years) 70/ Population Growth Rate(%) (70/20%=35 years)
Human Population Growth • Major reason for increasing human population growth rate is an increase in medical care, and a consequential decrease in death rates. • Doubling Time of a population (years) : 70 / Population Growth Rate (%) ( 70 / 2.0% = 35 years )