Fission takes place when an animal divides into two parts.
If the nucleus breaks up into lighter elements, it is called fission .
The nucleus breaks up into lighter elements when an animal divides into two parts.
What breaks up into two lighter elements when an animal divides into two parts?

  - the blood cells
  - the heart
  - Energy.
  - the main element
  - heat energy
  - light energy
  - the nucleus
  - sensory neurons