A survivorship curve is a graphical representation of the number of individuals surviving in a population over time. It illustrates the different types of reproductive strategies used by different species.
Three types of survivorship curves have been identified - Type I, Type II, and Type III.
Type I survivorship curve is characterized by high survival rates in the early and middle life stages and a sharp decline in survival rates in later life stages. This type of curve is typically observed in species that have few offspring but invest heavily in their survival and care. These species typically have a longer lifespan and reproduce later in life. Examples include humans, elephants, and whales.
Type II survivorship curve is characterized by a constant rate of survival throughout the lifespan. This type of curve is typically observed in species where the risk of death is constant throughout their lives, irrespective of their age. Examples include lizards, rodents, and some birds.
Type III survivorship curve is characterized by high mortality rates in the early life stages and high survival rates in later life stages. This type of curve is typically observed in species that produce a large number of offspring but invest little in their survival and care. These species typically have a short lifespan and reproduce early in life. Examples include insects, fishes, and plants.
The survivorship curve illustrates the different reproductive strategies of these species. Type I species invest heavily in the survival and care of their offspring and have fewer offspring. Type II species have a constant risk of death throughout their lives and have a moderate number of offspring. Type III species produce a large number of offspring but invest little in their survival and care.