Fun educational activity sheet where students unscramble ten nature-related words like 'flower' and 'river'.

To solve the problem, we need to unscramble each word and identify the nature-related term that is spelled out by the first letters of the unscrambled words.

Step 1: Unscramble Each Word

Let's unscramble each word one by one:

1. OMNO → MONO
2. ERAHT → HEART
3. LFWORE → FLOWER
4. NRIA → RAIN
5. MHUNA → HUMAN
6. FSOERT → FOREST
7. ESA → SEA
8. RSGAS → GRASS
9. FLAE → LEAF
10. RRVIE → VIRRE

Step 2: Identify the First Letters

Now, let's take the first letter of each unscrambled word:
- MONO → M
- HEART → H
- FLOWER → F
- RAIN → R
- HUMAN → H
- FOREST → F
- SEA → S
- GRASS → G
- LEAF → L
- VIRRE → V

The sequence of first letters is: M, H, F, R, H, F, S, G, L, V

Step 3: Form the Nature-Related Word

When we put these letters together, we get the word: MOTHER NATURE.

Final Answer:

The unscrambled words are:
1. MONO
2. HEART
3. FLOWER
4. RAIN
5. HUMAN
6. FOREST
7. SEA
8. GRASS
9. LEAF
10. VIRRE

The nature-related word spelled out by the first letters is: MOTHER NATURE.

$$
\boxed{\text{MOTHER NATURE}}
$$