7.6 Reproductive Strategies and Population Fluctuations Species can be divided into two broad categories based on their reproductive strategies: K-strategists: Organisms that typically reach a stable population as the population reaches the carrying capacity. r-strategists: Typically, these are small organisms that have a short life, produce many offspring, exploit unstable environments, and do not reach a carrying capacity.

7.6 Reproductive Strategies and Population Fluctuations K-strategist characteristics include: Usually occupy relatively stable environments Large organisms Long-lived Produce few offspring Provide substantial parental care Reproductive strategy is to invest a great deal of energy in producing a few offspring that have a good chance of living to reproduce.

7.6 Reproductive Strategies and Population Fluctuations r-strategist characteristics include: Small, short-lived organisms Produce many offspring Little if any parental care Exploit unstable environments Usually do not reach carrying capacity (boom-bust cycles) Reproductive strategy is to produce large numbers of offspring to overcome high mortality.

7.7 Human Population Growth The human population growth curve has a long lag phase followed by a sharply rising exponential growth phase Still rapidly increasing A major reason for the increasing human population growth rate is an increase in medical care Leads to decrease in death rates

7.7 Human Population Growth Historical human population growth

7.7 Human Population Growth The doubling time for the human population is calculated by: 70 / annual rate of increase (%) ( 70 / 2.0% = 35 years )

7.7 Human Population Growth Doubling time for the human population