Survivorship Curves

Overview

• Different species exhibit unique reproductive strategies and survival patterns over their life spans.

• These patterns influence how populations respond to various environmental factors.

• Survivorship curves graphically represent these survival patterns as a function of age.

Types of Survivorship Curves

Type I Survivorship Curve

• Characteristics:

  • High survival rates throughout most of life.

  • Increased mortality occurs in old age.

• Examples:

  • K-selected species like elephants, whales, and humans (especially in developed countries).

Type II Survivorship Curve

• Characteristics:

  • Relatively constant decline in survivorship throughout life.

• Examples:

  • Chipmunks, squirrels, and certain raptors.

  • Includes K-selected species that provide substantial parental support.

Type III Survivorship Curve

• Characteristics:

  • High mortality early in life, with few individuals reaching adulthood.

  • Those that survive to adulthood tend to live longer.

• Examples:

  • r-selected species like mosquitoes, many fish, dandelions, and frogs.

  • Frogs have a high death rate in early stages (eggs and tadpoles) but live long as adults due to camouflage and quick reflexes.

Influencing Factors

• The interaction of species type (generalist or specialist), reproductive strategy (r- or K-selected), and survivorship curves affects species survival and success.

• Human activities exert pressure on populations, influencing these factors and the potential for species survival.

Conclusion

• The module discusses how species differences lead to various reproductive strategies, impacting survivorship and longevity.

• Future exploration will focus on how these traits affect population size, growth, and the carrying capacity of ecosystems.