Survivorship curve

Definition

A survivorship curve is a graphical representation that shows the number of individuals surviving at each age for a given species or population. It illustrates the mortality rates and life expectancy across different life stages, helping to classify species into different categories based on their reproductive strategies and survival patterns.

5 Must Know Facts For Your Next Test

1. Survivorship curves can be divided into three main types: Type I shows high survival in early and middle life with a rapid decline in older age; Type II depicts a constant death rate regardless of age; and Type III illustrates high mortality in early life but a higher chance of survival for those who make it past early stages.
2. The shape of a survivorship curve is influenced by environmental factors, resource availability, and predation pressures, which can affect the overall population dynamics.
3. Species with Type I curves, such as humans and many large mammals, typically invest more in parental care and have fewer offspring, while species with Type III curves, like many fish and amphibians, produce many offspring with little to no parental care.
4. Survivorship curves are essential tools for ecologists and conservation biologists as they help assess population health, predict future trends, and implement conservation strategies for endangered species.
5. Changes in survivorship curves over time can indicate shifts in environmental conditions, resource availability, or other ecological factors affecting a population.

Review Questions

• How do the different types of survivorship curves reflect the reproductive strategies of various species?
  • The different types of survivorship curves—Type I, II, and III—reflect distinct reproductive strategies among species. Type I species, like humans, invest significant resources in raising fewer offspring to ensure their survival into adulthood. Type II species maintain a relatively constant survival rate throughout their lives, suggesting a balanced approach to reproduction. In contrast, Type III species produce many offspring with little parental investment, leading to high mortality in early life stages but allowing for some to survive into adulthood.
• Discuss the importance of survivorship curves in understanding population dynamics and conservation efforts.
  • Survivorship curves play a critical role in understanding population dynamics by providing insights into mortality rates and life expectancy across various ages. This information helps ecologists identify trends in population health and structure. For conservation efforts, survivorship curves can indicate which species may be at risk due to declining survival rates or changes in reproductive success, guiding targeted management strategies to protect vulnerable populations.
• Evaluate how environmental changes might impact the shape of a survivorship curve for a particular species.
  • Environmental changes can significantly impact the shape of a survivorship curve for any given species by altering mortality rates or reproductive success. For instance, if habitat destruction leads to increased predation or reduced food availability for a species with a Type I curve, we might observe an increase in juvenile mortality rates. This shift could transform the curve from Type I towards Type III characteristics over time. Similarly, climate change may affect reproductive timings or conditions needed for survival, ultimately reshaping the curve as populations adapt or decline.

Related terms

Life Table: A table that displays the age-specific mortality and survival rates of a population, providing essential data for constructing survivorship curves.

Reproductive Strategies: The strategies that species use for reproduction, which can influence their survivorship curves, including traits like fecundity and parental care.

Type I, II, and III Curves: The three general types of survivorship curves that categorize species based on their patterns of survival: Type I (high survival rates in early life), Type II (constant survival rates), and Type III (low survival rates in early life).