Deck 21: Decomposition and Nutrient Cycling

Question 1

In an estuary, the zone of maximum vertical difference in density is called a(n)________.

Answer 1

pycnocline

Question 2

Outline the decomposition sequence for leaf litter and which functional groups are responsible for which stages.

Answer 2

In living, senescing tissue, first epiphytic fungi, then endophytes and weal parasites and pathogens colonize internal tissue. Once dead, pioneer saprophytic fungi consume sugar, polymer degrading fungi breakdown cellulose and hemicellulose, and lignin degrading fungi break down the recalcitrant compound lignin, followed by secondary opportunists.

Question 3

The initial phase of animal decomposition is

A)extracellular digestion.
B)liquefaction.
C)putrefaction.
D)autolysis.

Answer 3

D

Question 4

Which of the following is NOT a component of plant tissue?

A)simple sugars
B)cellulose
C)chitin
D)lignin

Question 5

In streams and rivers, nutrients are continually transported downstream, a process better described as nutrient ________ than nutrient cycling.

Question 6

Animals that feed on bacteria and fungi are called ________.

Question 7

The last organic compound to be decomposed in plant matter is

A)cellulose.
B)lignin.
C)sugar.
D)humus.

Question 8

The release of organically bound nutrients into an inorganic form is called ________.

Question 9

The dominant decomposers of dead animals are ________.

Question 10

In plants, the absorption of a portion of nutrients from senescing tissues in order to use the nutrients for production of new tissues is called

A)leaching.
B)reabsorption.
C)recycling.
D)transpiration.

Question 11

The breakdown of chemical bonds that were formed during the construction of plant and animal tissues is called ________.

Question 12

Which of the following is NOT an important process involved in decomposition?

A)leaching
B)fragmentation
C)mineralization
D)transpiration

Question 13

The major decomposers of dead plant tissues are

A)amoeba.
B)bacteria.
C)fungi.
D)insects.

Question 14

In open water, the undissolved remains of dead organisms and other organic material that drifts toward the bottom are called ________ organic matter.

Question 15

The rate of nutrient cycling in an ecosystem depends on the rates of two key processes: primary productivity and ________.

Question 16

________ is the process by which plants absorb a portion of their nutrients from senescing tissues to be stored and used for the production of new tissues.

Question 17

Which of the following organisms are NOT important agents of decomposition?

A)plants
B)bacteria
C)fungi
D)soil invertebrate animals

Question 18

Which of the following breaks down the slowest during decomposition?

A)simple sugars
B)cellulose
C)chitin
D)lignin

Question 19

The incorporation of mineral nutrients into an organic form is called ________.

Question 20

In a process known as the ________, the rise and fall of water depth with tidal cycles brings nutrients into coastal marshes from coastal ocean waters.

Question 21

Decomposers obtain their energy by photosynthesis.

Question 22

Fungi are the dominant decomposers of dead animal matter, whereas bacteria are the dominant decomposers of dead plant matter.

Question 23

The physical fragmentation of organic matter into smaller pieces is achieved primarily by invertebrate detritivores.

Question 24

All heterotrophs function, to some degree, as decomposers.

Question 25

The process of conversion of nutrients from an organic form into an inorganic form that plants can use is called

A)immobilization.
B)respiration.
C)transpiration.
D)mineralization.

Question 26

Aerobic bacteria are decomposers, but anaerobic bacteria are not.

Question 27

The rate of decomposition is greatest in

A)cold and moist environments.
B)cold and dry environments.
C)warm and moist environments.
D)warm and dry environments.

Question 28

In ________, the process of nutrient cycling is sometimes described as nutrient spiraling.

A)streams and rivers
B)oceans
C)lakes
D)forests

Question 29

In open water ecosystems, decomposition occurs primarily in the

A)thermocline.
B)hypolimnion.
C)epilimnion.
D)benthic zone.

Question 30

Bacteria, fungi, and animals are all important in decomposition.

Question 31

Compounds resistant to decomposition are known as

A)labile.
B)recalcitrant.
C)cellulose.
D)humus.

Question 32

The rate of decomposition is faster for proteins, simple sugars, cellulose, and hemicellulose than it is for lignin.

Question 33

Most of the nutrients in the leaves of a deciduous plant are lost when the leaves senesce and drop to the ground.

Question 34

Aquatic arthropods that fragment organic particles and also eat bacteria and fungi on the surface of the litter are called

A)shredders.
B)filtering collectors.
C)gathering collectors.
D)grazers.

Question 35

Litterbags can be used to estimate the rate of decomposition.

Question 36

In an estuary, the zone of maximum vertical difference in density of water layers is called the

A)thermocline.
B)pycnocline.
C)mixing zone.
D)hypolimnion.

Question 37

Coastal zones of contact between freshwater from streams and rivers and salt water from the ocean are called

A)estuaries.
B)headwaters.
C)deltas.
D)coastal upwelling zones.

Question 38

Soil organic matter typically has a residence time of ________ years.

A)1 - 2
B)20 - 50
C)50 - 100
D)> 1000

Question 39

Which of the following statements is TRUE?

A)The rate of nutrient cycling in an ecosystem depends only on the rate of photosynthesis.
B)The rate of nutrient cycling in an ecosystem depends only on the rate of decomposition.
C)The rate of nutrient cycling in an ecosystem does not depend on the rate of photosynthesis or the rate of decomposition.
D)The rate of nutrient cycling in an ecosystem depends on both the rate of photosynthesis and the rate of decomposition.

Question 40

Roots can alter the chemical environment of the rhizosphere by exuding

A)carbon.
B)nitrogen.
C)enzymes.
D)nothing. Toots can only absorb, they cannot exude.

Question 41

Explain how the "quality" of plant-derived organic matter changes during the course of decomposition.

Question 42

The release of organically bound nutrients into an inorganic form is called immobilization.

Question 43

Using nitrogen cycling, explain the feedback between primary production and decomposition.

Question 44

In open-water ecosystems, turnover prevents the movement of nutrients between the bottom and surface layers.

Question 45

Describe three different processes that are important for decomposition. Explain which organisms are important for each of the processes.

Question 46

During the process of decomposition, carbon quality typically declines.

Question 47

In salt marshes, only a small portion of primary production is consumed by herbivores.

Question 48

Coastal ecosystems are not very productive because they are usually cool.

Question 49

Estuaries receive nutrients both from tides and from streams and rivers.

Question 50

Nutrient "spiraling" occurs in streams and rivers.

Question 51

Decomposition proceeds faster in moist environments than in dry environments.

Question 52

The rate of nutrient cycling in an ecosystem is a function of physical characteristics of the ecosystem, not biological processes such as photosynthesis and decomposition.

Question 53

Aerobic decomposition occurs at a faster rate than anaerobic decomposition.

Question 54

Describe one major difference between nutrient cycling in a river and nutrient cycling in a lake.

Question 55

Describe the process of upwelling in the ocean and how it relates to fisheries.

Question 56

The region of the open ocean where the north and south equatorial currents meet is deficient in nutrients and supports little life.

Question 57

Describe the soil microbial loop.

Question 58

In open-water systems such as lakes and oceans, decomposition occurs mostly in the surface layer.

Question 59

Discuss the effects of temperature, humidity, and oxygen availability on the rate of decomposition.

Question 60

Define mineralization and immobilization, and discuss the differences between them.

Question 61

Describe how you might go about measuring the rate of decomposition of leaf litter in the upper layer of a forest soil.