What You Need to Know

Key Concept Diagram

Decomposers include bacteria and fungi; they break down complex organic molecules into simpler ones

Decomposition returns nutrients (nitrogen, phosphorus, carbon) to the soil and atmosphere

The carbon cycle, nitrogen cycle, and phosphorus cycle all depend on decomposition

Factors affecting decomposition rate: temperature, moisture, oxygen availability, and pH

Key Vocabulary

Decomposer

An organism (bacteria or fungi) that breaks down dead organic matter

Nutrient cycle

The movement of nutrients through the environment, organisms, and back again

Humus

Organic matter in soil formed by partial decomposition of plant and animal material

Carbon cycle

The movement of carbon through the atmosphere, living organisms, and Earth

Knowledge Check

Select the correct answer for each question. Click "Check Answer" to see if you are right.

Question 1

What happens to nutrients in dead plant and animal material if decomposers did not exist?

They would remain locked in dead material, unavailable to living organisms They would float into the atmosphere immediately They would dissolve in rainwater They would be eaten by herbivores

Question 2

Warm, moist conditions speed up decomposition because:

Heat kills all the decomposers These conditions support maximum bacterial and fungal activity Moisture prevents oxygen from reaching the material Cold temperatures speed up microbial activity

Question 3

The nitrogen cycle depends on decomposers because:

Decomposers produce nitrogen gas Plants can absorb nitrogen directly from dead animals Decomposers release ammonium ions from dead organic matter, making nitrogen available to plants Decomposers turn nitrogen gas into organic matter

Decomposition and Nutrient Cycling