Select the correct statements regarding to the growth curves:

a) J shaped curve is realistic in nature.

b) Algal bloom is an example of exponential growth curve.

c) S shaped curve is realistic in nature.

d) Yeast is an example of logistic growth.

b ,c and d.

The correct answer is option (3) - b ,c and d.

Two types of growth models are known:

Exponential growth: Resource (food and space) availability is obviously essential for the unimpeded growth of a population. Ideally, when resources in the habitat are unlimited, each species has the ability to realise fully its innate potential to grow in number. Then the population grows in an exponential or geometric fashion. Algal bloom shows this type of growth curve. If in a population of size N, the birth rates (not total number but per capita births) are represented as b and death rates (again, per capita death rates) as d, then the increase or decrease in N during a unit time period t (dN/dt) will be

dN/dt =rN

The r in this equation is called the ‘intrinsic rate of natural increase’ and is a very important parameter chosen for assessing impacts of any biotic or abiotic factor on population growth. Exponential or geometric growth pattern of a population and results in a J-shaped curve when we plot N in relation to time.

Logistic growth: A population growing in a habitat with limited resources show initially a lag phase, followed by phases of acceleration and deceleration and finally an asymptote, when the population density reaches the carrying capacity. A plot of N in relation to time (t) results in a sigmoid curve. This type of population growth is called Verhulst-Pearl Logistic Growth. yeast is an example of logistic growth curve and is described by the following equation:

Where N = Population density at time t, r = Intrinsic rate of natural increase, K = Carrying capacity.