Plastids are organelles found exclusively in plant cells and some algae. They are responsible for important functions like:

* Photosynthesis: Chloroplasts, a type of plastid, contain chlorophyll and carry out photosynthesis, converting light energy into chemical energy.

* Storage: Other plastids, such as amyloplasts, store starch.

* Pigmentation: Chromoplasts are responsible for the colors of fruits, flowers, and leaves.

Animal cells do not have the ability to perform photosynthesis and rely on consuming food for energy. They also lack the specific genes and mechanisms necessary to develop plastids.