APES Video Notes 3.3 - Survivorship Curves

Survivorship Curves

  • Definition: A survivorship curve plots the number of individuals still alive at each age for a cohort (group born at the same time).

  • Y-axis: Survivorship (number or proportion of individuals alive).

  • X-axis: Age of individuals (time).

Chapter 2: Objectives

  • Key Points to Understand:

    • A survivorship curve shows survival rates for a cohort.

    • Three basic types of survivorship:

      • Type 1: High juvenile survivorship, lower mortality in early life (K selected species).

      • Type 2: Constant mortality rate throughout life (birds, rodents).

      • Type 3: Low juvenile survivorship, high mortality early on (R selected species).

  • Survivorship Curves:

    • Type 1 curve is relatively flat at the start with steep decline in older age.

    • Type 3 curve shows fast decline early in life, with few surviving to adulthood.

Chapter 3: Survivorship Types

Type 1 Survivorship

  • Characteristics: High parental care leads to high survivorship in early and midlife.

  • Examples:

    • Grizzly Bears: Protecting cubs from threats.

    • Chimpanzees: Nursing and safeguarding offspring.

  • Decline: Sharp decrease in survivorship as individuals reach old age.

Type 2 Survivorship

  • Characteristics: Intermediate parental care, with somewhat constant mortality.

  • Examples: Birds and rodents experienced consistent decline, influenced by vulnerability to predators and environmental factors.

Type 3 Survivorship

  • Characteristics: Low parental care resulting in high mortality rates for young.

  • Examples:

    • Insects, Fish, and Plants: High number of offspring compensates for low survivorship.

  • Lifespan Pattern: Most die in early life but some survive to slow decline in adulthood.

Graph Interpretation

  • Graphs show survivorship relative to the overall lifespan of the species depicted.

  • Units of age on the x-axis are relative, allowing for comparison across species with vastly different maximum lifespans.

  • Insights:

    • Example: Dandelions vs. Whales: different lifespans but percentage reaching maturity is comparable on a relative scale.

Conclusion

  • FRQ Practice: Analyze and describe trends in survivorship data. Justify the type of survivorship curve represented.

  • Closing: Reminder to engage with content and subscribe for updates.