Module 13: Organic Matter and the Food Web

Question 1

Define active organic matter.

Answer 1

Part of the organic matter that microorganisms feed on

Question 2

Define consumer.

Answer 2

Obtain energy and carbon by feeding on other organisms or their waste product

Question 3

Define humus.

Answer 3

Organic matter that has been transformed by microorganisms to the point where it doesn’t decompose further or decomposes very slowly

Question 4

Define soil food web.

Answer 4

Community of organisms in the soil

Question 5

Define producer.

Answer 5

Use energy from sun to conduct photosynthesis and fix carbon dioxide

Question 6

What are the components of soil organic matter?

Answer 6

Living organisms (under 5%)
Fresh residue (under 10%)
Humus (33%-50%)
Decomposing organic matter (33%-50%)

Question 7

What are the differences between bacteria and fungi in the breakdown of organic matter?

Answer 7

Bacteria use simpler organic compounds.

Fungi use complex organic compounds.

Question 8

What materials make up humus?

Answer 8

Lignin
Amino acids
Nitrogenous compounds

Question 9

What are the conditions that affect the formation of humus?

Answer 9

Amount and type of plant residues (greater in prairie soils than forest soils)

Climate condition (greater under moist and cool rather than dry and hot)

Question 10

What techniques can maintain organic matter levels in soil?

Answer 10

Reduce or eliminate tillage
Reduce soil erosion
Proper fertilization
Cover crops

Question 11

What are examples of producers?

Answer 11

Plants
Lichens
Some bacteria
Algae

Question 12

What are some examples of consumers?

Answer 12

Nematodes
Anthropods
Birds
Animals
Earthworms
Small vertebrates

Question 13

What are the benefits of the soil food web?

Answer 13

Decompose organic compounds

Sequester nutrients

Fix nitrogen

Improve soil structure

Feed on pests

Food supply for aboveground animals