20: Soil Biology 2

Question 1

What size are soil microorganisms? What are they?

Answer 1

Less than 4 μm
Viruses, archaea, fungi, bacteria, protists

Question 2

What types of soil organisms are there?

Types and more specific examples (ex: acellular –> more specific example viruses)

Answer 2

1: Acellular organisms
- Viruses

2: Prokaryotes (no cell nucleus)
- Bacteria
- Archaea

3: Eukaryotes (real nucleus and organelles)
- Fungi
- Protists

Question 3

Soil viruses

What are they
What size
What do they parasitize?

Answer 3

Acellular structures composed of a central nucleic acid core (DNA, RNA) with a protein or lipid cover

Size: 0.01-1 μm long

Internal parasites of plant, animals, bacteria, and fungi

Question 4

What is the ecological role of viruses?

Answer 4

In aquatic ecosystems they may contribute to 25-85% of bacterial mortality, therefore having a strong effect on microbial processes, releasing large amounts of nutrients contained in bacteria and therefore contributing to nutrient turnover

Question 5

Archaea

Answer 5

Unicellular, prokaryotic, and high variety of cell shapes.

Are ubiquitous in mesophilic and ‘normal’ environments, play a key role in C and N cycles

Question 6

Bacteria

Answer 6

Prokaryotic, unicellular, and high variety of cell shapes.

Able to carry out a wide array of chemical and metabolic reactions. Aerobic and anaerobic. Use organic or inorganic sources of energy

Most numerous and diverse, smallest.

Question 7

Different types of bacteria

Answer 7

Photoautotrophs, lithoautotrophs, lithoheterotrophs

Question 8

Fungi

Answer 8

Eukaryotic, uni- or multicellular

Highly abundant: largest biomass in soils (forests) together with bacteria

Question 9

Fungal morphology

Answer 9

Single celled: yeasts
Multicellular: cells are arranged in filaments called hyphae, which are separated by septa. Septa are porous membranes that separate cells and tha tallow the movement of fluids and organelles

Question 10

Ecological roles of fungi

Answer 10

Saprotrophic fungi (decomposition)
Symbionts (live in close interaction with plants)

Question 11

Protists

Answer 11

Diverse morphology
Diverse functions and metabolism
The different groups of protists do not have much in common

Question 12

Ecological roles of protists

Answer 12

Diverse, can be saprotrophs, symbionts, microbial grazers

Question 13

Microbial grazers

What do thye do and how do they affect bacteria and fungi populations?

Answer 13

Feed on the primary decomposers (bacteria, fungi, actinomycetes)

Up to a certain degree, stimulates the growth of bacteria and fungi

Grazing releases nutrients

Question 14

What size are soil microfauna?
What are they?

Answer 14

2μm-100μm
Nematodes, rotifers, tardigrades

Question 15

Nematodes

Morphological organization
What do they eat?
Digestive system

Answer 15

Unsegmented roundworms
Simple morphological organization: no circulatory, endocrine, or respiratory system (breath through skin)
Plant parasites of microbivores
Digestive system (tube within a tube): foregut used to classify nematodes depending on feeding habits

Question 16

Rotifers

Size
Body
Habitat

Answer 16

Small (0.2-0.5 mm) but complex multicellular organisms with a specialized digestive system

Body divided into head, trunk, and foot

Habitat: live in soil water films. Well-developed cuticle that protects them from desiccation

Question 17

Tardigrades

What’s special about them?

Answer 17

Survive extreme conditions through cryptobiosis: their metabolism drops to 0.01% of normal and the water content of the body decreases to less than 1%

Can survive up to 200 years in cryptobiosis

Question 18

What size are soil mesofauna?
What roles do they perform?

Answer 18

100μm-2mm
They are detritivores, microbial grazers, and predators

Question 19

What size are soil macrofauna?
What is special about them?

Answer 19

More than 2 mm
Ecosystem engineers