Lecture 6 -- Biotic Interactions: Logs and Fungi

Question 1

What tissue in tree trunks produces the xylem and phloem? What does xylem transport? Phloem?

Answer 1

Cambium produces them.
Xylem transports nutrients and water from the roots.
Phloem transports sugars/sap from photosynthesis throughout tree.

Question 2

What is heartwood, and what is its role?

Answer 2

Dead layers of xylem (composed of cellulose and lignin). Provided the tree with a strong, rigid, vertical structure resistant to rot.

Question 3

T/F: most of a tree is made up of living cells.

Answer 3

False

Question 4

What is the difference between a monosaccharide and a polysaccharide? What is the most common form of organic matter used by cells as a source of energy to drive respiration?

Answer 4

Monosaccharides are simple carbohydrate molecules. Polysaccharides are complex carbohydrates, chains of monosaccharides bound together.

Question 5

T/F: maple syrup is a monosaccharide.

Answer 5

False

Question 6

How do standing snags and fallen logs differ in terms of their ecological roles?

Answer 6

fallen logs provide more nutrients than living trees

Question 7

Describe how a pileated woodpecker may be part of a commensalism with a tree-nesting tree swallow.

Answer 7

It may leave a hole in a tree, which benefits the swallow with a place to nest. But the woodpecker receives no benefit from the swallow.

Question 8

T/F: both species benefit in a commensalism.

Answer 8

False

Question 9

Why are fallen logs called nurse logs? Why are tree seedlings that grow on nurse logs often more successful than seedlings on the forest floor?

Answer 9

Closer to sunlight
More nutrients from the dead log
Off the floor, out of grazing range of deer/animals

Question 10

What proportion of the weight of a decaying log may be made up of living cells?

Answer 10

20%

Question 11

Name three kinds of animals that use fallen logs as habitat.

Answer 11

ambrosia beettle, voles, warblers??

Question 12

How do truffles and red backed voles depend on each other?

Answer 12

The truffles are tasty and voles eat them— get covered in spores which they spread!

Question 13

How are ambrosia beetles attracted to newly fallen logs? Describe the symbiosis between ambrosia beetles and fungi.

Answer 13

By the smell?? I cant remember

Question 14

What role do logs play in streams and rivers?

Answer 14

Slow stream flow so channels aren’t scoured (protects fish and other life in rivers).

Question 15

How do beavers affect habitat in river systems? How do beavers affect coho salmon habitat?

Answer 15

Create ponds and stillwaters where photosynthesizers flourish and fish have abundant food.

Question 16

T/F: historically, beaver ponds were found to produce more than half of all coho salmon smolts in the Stillaguamish river.

Answer 16

True

Question 17

T/F: Under current conditions, beaver ponds produce more than half of all coho smolts in the Stillaguamish River.

Answer 17

False

Question 18

What is the concept of shifting baselines? Why is this a key challenge in science and society? Why does it matter?

Answer 18

A change in the reference point we measure something against.
Challenge: idea of what is “normal” or “natural” depends on generation defining it. As time passes, we lose idea of what was originally there. What we see as normal may actually be result of change or disruptions.

Question 19

What is an independent variable in a hypothesis? A dependent variable?

Answer 19

Independent– The one you are studying/ changing to see impact on dependent. (input)

Dependent– the one that changes! (output)

Question 20

Whats the difference between a fungal hyphae and a mycelium?

Answer 20

Hyphae are the individual filaments that make up the underground body of fungi. Mycelium is the entire mass of a fungus’ hyphae.

Question 21

Why are mycorrhizae important to plants?

Answer 21

They increase the plants’ ability to uptake necessary nutrients and water from the soil.

Question 22

What is a siderophore?

Answer 22

Chemical released by fungi or bacteria that modifies metals into a form plants can uptake and use.

Question 23

Describe three ways in which trees benefit from mychorrhizae.

Answer 23

Water and nutrient uptake
Mychorrhizae release antibiotics that kill harmful bacteria in soil
Decompose tough debris in soil (including lignin and rock) for nitrogen

Question 24

How much of a tree’s photosynthate is shared directly by the tree with its rhizosphere ecosystem?

Answer 24

40%

Question 25

Up to how much of the biomass found in soil can be from fungal hyphae?

Answer 25

50%