What might cause a virus in the lysogenic cycle to suddenly enter the lytic cycle?

Environmental stressors such as starvation or exposure to toxic chemicals may cause the prophage to be excised and enter the lytic cycle.  

Explanation:

Lysogenic stages and Lytic stages are all found within the Life Cycle of the Virus.

In a lysogenic cycle, the phage genome also enters the cell through attachment and penetration. A good example of a phage with this kind of life cycle is the lambda phage. During the lysogenic cycle, the phage genome integrates into the bacterial chromosome and becomes part of the host. instead of killing it.

During the lytic cycle of virulent phage, the bacteriophage takes over the cell, reproduces new phages, and destroys the cell.

Cheers!

≅200-130 milions years ago pangea splited in 2 continents