Here's why:

* Cellular respiration is the process of breaking down glucose (sugar) in the presence of oxygen to release energy in the form of ATP. This energy is essential for all living cells to carry out their functions.

* While plants can produce their own glucose through photosynthesis, they still need to break it down through cellular respiration to access the energy within it.

* Animal cells cannot produce their own glucose and rely on consuming food to obtain it. They then break down this glucose through cellular respiration to get the energy they need.

So, even though plants have unique abilities like photosynthesis, both plant and animal cells share the fundamental need for cellular respiration to power their activities.