Question

1. What are the three types of species dispersion pattern? Give an example of each.

2. How do we calculate mortality rate?

3. Survivorship can be calculated using the following formula: proportion of individual cohort that survive to age “x” or (x ÷ by original cohort). The resulting data can be used to create a survivorship curve. Differentiate between the three major types (I, II, III).

Answer 1

1. Three type of species dispersion pattern

a).uniform dispersion-Uniform dispersion is observed in plant species that inhibit the growth of nearby individuals. For example, the sage plant, Salvia leucophylla

b).Random dispersion-Random dispersion occurs with dandelion and other plants that have wind-dispersed seeds that germinate wherever they happen to fall in a favorable environment

c).Clumped dispersion-Clumped dispersion is seen in plants that drop their seeds straight to the ground, such as oak trees, or animals that live in groups.

2.Calculation of mortality rate

  Total number of new death in a defined period of time

  Total number of person in population at the begining period.

3.Type 1- Type I or convex curves are characterized by high age-specific survival probability in early and middle life, followed by a rapid decline in survival in later life. They are typical of species that produce few offspring but care for them well, including humans and many other large mammals.

Type 2-A type II survivorship curve shows a roughly constant mortality rate for the species through its entire life. This means that the individual's chance of dying is independent of their age. Type II survivorship curves are plotted as a diagonal line going downward on a graph.

Type 3-A type III survivorship curve depicts species where few individuals will live to adulthood and die as they get older because the greatest mortality for these individuals is experienced early in life. This type of survivorship curve is drawn as a concave curve on a graph.