Here's why:

* Mitochondria are the powerhouses of the cell. They are responsible for producing ATP (adenosine triphosphate), the primary energy currency of cells.

* Both plants and animals need energy to survive and carry out their functions. Plant cells use mitochondria to power processes like photosynthesis and growth. Animal cells use mitochondria to power movement, muscle contraction, and other energy-demanding activities.

Let me know if you have any other questions about cells!