Question

Question was provided via image upload.

Explanation:

Identify the topic and structure

The question is titled "1.3 Sustaining Terrestrial Ecosystems" and asks to fill in blanks representing the layers of a soil profile (soil horizons) from top to bottom.
We apply our knowledge of Terrestrial Ecosystems and Soil Horizons.

Analyze the sequence of soil horizons

The standard soil profile consists of the following horizons from top to bottom:

1. O Horizon: Organic matter / litter layer (Blank #1 is filled with "organic matter").
2. A Horizon: Topsoil (Blank #2 is filled with "topsoil").
3. E Horizon: Eluviation / leaching layer (sometimes omitted in basic profiles, but usually subsoil follows topsoil).
4. B Horizon: Subsoil (Blank #3).
5. C Horizon: Parent material / weathered rock (Blank #4).
6. R Horizon: Bedrock.

Determine the missing blanks

Based on standard high school environmental science curricula:

• Blank #1: organic matter (O horizon)
• Blank #2: topsoil (A horizon)
• Blank #3: subsoil (B horizon)
• Blank #4: parent material (C horizon)

Answer:

Question 1

• Blank #1: organic matter
• Blank #2: topsoil
• Blank #3: <blank>subsoil</blank>
• Blank #4: <blank>parent material</blank>