Lecture Notes: Survivorship Curves (Topic 3.3)

Introduction

• Topic: Survivorship Curves, building on Topic 3.2 R and K Selected Species.
• Objective: Explain survivorship curves, including understanding the survival rates of cohorts.

Key Concepts

R and K Selected Species

• R Selected Species: Typically have many offspring with little parental care.
• K Selected Species: Have fewer offspring with significant parental care.

Survivorship Curves

• Definition: A graphical representation of the number of individuals in a cohort that survive to each age.
• Axes:
  • Y-Axis: Proportion of individuals alive.
  • X-Axis: Time or age.

Types of Survivorship Curves

Type 1 Survivorship

• Characteristics:
  • High survivorship during infancy and childhood.
  • Rapid decline in older age.
• Examples: Humans, whales.
• K-Selected Species: High parental care leads to high early survivorship.

Type 2 Survivorship

• Characteristics:
  • Steady decline in survivorship throughout life.
• Examples: Birds, rodents.
• Medium Parental Care: Some care but limited protective ability.

Type 3 Survivorship

• Characteristics:
  • High mortality rate early in life.
  • Survivorship levels off for those few reaching middle and old age.
• Examples: Insects, fish, plants (e.g., dandelions).
• R-Selected Species: Little to no parental care leads to high offspring numbers to offset mortality.

Important Notes

• Relative Age: Age on graphs is relative, not absolute (e.g., dandelions vs. whales lifespan).
• Cohort: Group of individuals of the same species born at the same time.

Skills and Practice

• FRQ Focus: Data analysis, describing trends in survivorship data.
• Task: Describe trends and justify the type of survivorship curve represented.

Conclusion

• Encouragement to review related materials and engage in continuous learning.
• Reminder of resources available for further study and practice.