Question

Given below is a graph showing the growth of yeast. This is the type of growth curve noted in most organisms. What does the segment C-D indicate?

• A. No new individuals are formed.
• B. Death rate is zero.
• C. The rate of formation and rate of death of individuals is the same.
• D. The experiment stopped.

Answer 1

The correct option is C The rate of formation and rate of death of individuals is the same.

• The given graph is the sigmoid growth curve seen during geometric growth. Initially the growth is slow which is the lag phase. The yeast exhibits lag phase from A to B.
• The second phase is the log phase or the exponential phase, here the cells undergo repeated mitotic division. The log phase is from B to C in yeast cells.
• When the nutrient supply is limited the growth slows down leading to a stationary phase. In this phase the formation of yeast cells and the death of yeast cells is the same. Cell division slows down. It is seen from C to D.
• The last phase is also called the death phase. In this phase, the yeast cells begin to die due to the lack of nutrients or the presence of poisonous byproducts from the reaction. It is indicated from D to E.