Prefix.

2. converts into a coded form.
6. throw 'back'
8. the large muscle at the front of the thigh, which is divided into four distinct portions and acts to extend the leg.
11. study of 'life'
12. the surroundings or close off on all sides.
13. meaning"heat before". ...
16. meaning "come before". They tried to prevent an accident by taking the appropriate safety measures.

1. move 'back'
3. writer of 'time'
4. a biological community of interacting organisms and their physical environment
5. instrument that measures 'time'
7. the position of the moon or a planet when it is 90°
9. or to the environment
10. a 'life' history.
14. stretch 'out'
15. go 'out'