Answers:

1. RIDE/RID (Extra letter: E)

2. HAT/THAT (Extra letter: T)

3. ART/PART (Extra letter: P)

4. ATE/LATE (Extra letter: L)

5. ILL/HILL (Extra letter: H)

6. EAR/EARN (Extra letter: N)

7. MAT/MEAT (Extra letter: E)

8. WAY/AWAY (Extra letter: A)

Challenge:

The extra letters are: E, T, P, L, H, N, E, Α.

The 8-letter word for an animal is:

ELEPHANT