Week 9 - Below Ground

Question 1

Name the four layers of soil

Answer 1

A horizon
B horizon
C horizon
Below

Question 2

What is the A horizon?

Answer 2

Topsoil
Sand, salt and clay
ROOTS

Question 3

Explain the B horizon

Answer 3

Sand, silt, clay
Less organic matter than in the A horizon

Question 4

Explain the C horizon

Answer 4

Partially broken up rock

Question 5

Explain the Below

Answer 5

Parent bedrock
Groundwater

Question 6

Name and explain the two types of rock weathering

Answer 6

Mechanical weathering
Water freezing and unfreezing and roots growing causes rocks to break up.

Chemical weathering
Acids released by plants and microorganisms break up rocks.

Question 7

Name the soil particles in order of size (biggest to smallest)

Answer 7

Sand
Silt
Clay

Question 8

Describe sand soils

Answer 8

Great for oxygenation
Bad for water retention

Question 9

Describe silt and clay soils

Answer 9

Bad at oxygenation
Good at water retention

Question 10

What is the ideal soil for agriculture? What is it made up of?

Answer 10

Loam.
Equal parts sand silt and clay

Question 11

Explain how plant soils keep minerals from being runoff. What is the negative of this? Explain

Answer 11

Minerals are positively charged (cations). Soil is negatively charged. Cling together and wont be runoff but also cant get sucked up by roots

Question 12

Explain cation exchange

Answer 12

In root hairs
Proton pumps shoot out protons that compete with mineral cations to get the negatively charged soil.

They start to take over. K, Ca, Mg now just free in the soil can get sucked up

Question 13

What is topsoil made of?

Answer 13

1. Humus
   Dead or decaying matter that is decomposed beyond recognition. WATER RETENTION. NUTRIENTS. helps with CATION EXCHANGE
2. Living organisms
   ex: earthworms, insects, fungi, barcteria, etc
   Decompose humus

Question 14

What are the negatives of agriculture?

Answer 14

Soil erosion
Taxes water reserves
Stresses soils

Question 15

How do prairie grasses stop soil erosion?

Answer 15

Prairie grasses have two meters (vertical) stabilizes the earth

Question 16

What is salinization?

Answer 16

When we water feilds a part evaporates and lesves the solutes

If there’s too much water solutes, water will leave the plants by osmosis to fix the gradient

Question 17

What is the rhizosphere?

Answer 17

layer of soil that surrounds plant roots

Question 18

What are the bacteria that live in the rhizosphere called?

Answer 18

Rhizobacteria

Question 19

What are endophytes?

Answer 19

Bacteria that colonize plant roots and live in the cortex

Question 20

Why do plants give photosyntates to the soil?

Answer 20

To sponsor the growth of soil microorganisms

Question 21

What do microorganidms give to plants?

Answer 21

1. Produce hormones that can stimulate plant growth and antibiotics
2. Bind to toxins
3. Increase availability of soil nutrients

Question 22

What are the three ways that plants can get nitrogen?

Answer 22

1. Lightning. It splits the nitrogen triple bonds. Reacts with oxygen to get nitrates
2. Soil bacteria.
   Turn nitrogen triple bond into ammonia
3. Decomposition of humus
   Bact break down humus into amino acids then convert to ammonia

Question 23

What are mycorrhizae?

Answer 23

Plant and fungus symbiosis
Plant gets increased surface fungus gets sugar

Question 24

What is ectomycorrizae

Answer 24

Makes fungus sheath (mantle) over plant root

Question 25

What is arbuscular mycorrhizae

Answer 25

Evolution favoured this

Fungal hyphae pushes against plasma membrane of cortical cells. Tree-like shape for high surface area