The logistic population growth is expressed by the equation :

1. $\frac{dN}{dt}=rN\left(\frac{N-K}{N}\right)$

2. $\frac{dt}{dN}=Nr\left(\frac{K-N}{K}\right)$

3. $\frac{dN}{dt}=rN\left(\frac{K-N}{K}\right)$

4. $\frac{dN}{dt}=rN$

The population of an insect species shows an explosive increase in numbers during rainy season followed by its disappearance at the end of the season. What does this show?

1. S-shaped or sigmoid growth of this insect

2. the food plants mature and die at the end of the rainy season

3. Its population growth curve is of J-type

4. The population of its predators increases enormously