J-shaped Growth curve. Population grows exponentially and after obtaining peak value the population may abruptly decrease. It is shown by small population of reindeer experimentally reared in a natural environmental with plenty of food but no predators. It has only two phases :

1. Lag phase. It is period of adaptation of animals to new environment so is characterized by slow or no growth in population.

J-shaped growth curve.

2. Logarithmic or Exponential phase. It is characterized by rapid growth in population which continues till enough food is available. But with the increase in reindeer population, there is corresponding decrease in the availability of food which finally becomes exhausted, which leads to mass starvation and mortality. This sudden increase in mortality is called population crash.