Just check if it has all the characteristics of life.
1. Is it made of cells?
2. Does it metabolize?
3. Does it keep internal conditions stable? (Homeostasis)
4. Does it have organs?
5. Can it reproduce?
6. Does it grow/develope?
7. And does it respond to stimuli (poke a bug, it moves. flower grows towards the sun.)
If all of these are Yes, your specimen is in fact, living.
