Chapter 11 - The Flux of Matter and Energy through Ecosystems

Question 1

What is a standing crop?

Answer 1

It is the bodies of living organisms within a unit area, constituting a standing crop of biomass

ex. trees

Question 2

What is biomass?

Answer 2

It is the mass of organisms per unit area of ground/water, usually expressed in units of energy (ex. joules/sq. m), and dry organic matter (g/sq. m) or mass of carbon (g of C/sq. m).

Basically mass per area that could include all organisms

Question 3

What is primary productivity?

Answer 3

It is the rate at which biomass is produced per unit are or volume through photosynthesis and can be expressed in many different units (ex. GPP & NPP).

Rate of biomass production per area per time

Question 4

What is gross primary productivity (GPP)?

Answer 4

It is the total fixation of energy by photosynthesis, but a portion of this as respiratory heat (R auto)

Question 5

What is respiratory heat (R auto)?

Answer 5

It is a portion of the GPP that is respired away by primary producers and is lost as respiratory heat

Question 6

What is net primary productivity (NPP)?

Answer 6

It is GPP-R auto and represents the actual rate of new biomass production available for consumption by heterotrophs

Question 7

What is secondary productivity?

Answer 7

It is the rate of biomass production by heterotrophs

Question 8

What is net ecosystem productivity (NEP)?

Answer 8

It is the difference between GPP and the respiration of all organisms in an ecosystem (R total). It measures the net rate of accumulation/loss of OM, energy, or organic carbon from an ecosystem and is equivalent to NPP-R het (the respiration of heterotrophic organicms)

Question 9

What is a live consumer system?

Answer 9

It is when a portion of primary production is consumed by herbivores, which are then consumed by carnivores

Question 10

What is a decomposer system?

Answer 10

It is the other portion of NPP not eaten by herbivores but by detritivores and decomposers.

Question 11

What are the 2 groups of organisms responsible for decomposition of dead OM (aka detritus)?

Answer 11

1. Decomposers: bacteria and fungi

2. Detritivores: animals that consume dead OM

Question 12

What are the necessary (and limiting) factors of primary production?

Answer 12

• sunlight, CO2, H2O, and nutrients

- temp does have an influence on the rate of PP

Question 13

What is Liebig’s Law of the Minimum?

Answer 13

It states that the growth of a plant is limited primarily by one nutrient that is in relatively short supply (usually N or P). The nutrient that is the most important but least available will control NPP.

ex. tropics are more P-limited (old, weathered soil) and the boreal is more N-limited (young, nutrient-lacking soil)

Question 14

What is colimitation?

Answer 14

It is when both N and P are limiting to PP.

ex. occurs in temperate forests

Question 15

What are the most limiting factors in aquatic PP?

Answer 15

• nutrients (more responsive to limiting nutrients) and light (comes from phytoplankton)
• there is higher nutrient limitation b/c fewer nutrients are based on biomass

Question 16

What is eutrophication?

Answer 16

It is the process of excess nutrient enrichment and can lead to algal blooms, which are very damaging and deplete ecosystems of oxygen

Question 17

What is a positive feedback loop?

Answer 17

It is when one factor influences another factor and continues until it can no longer.

ex. high growth leads to high pop size which further increases growth rate and is only constrained by P

Question 18

Proportions of NPP flowing along each possible energy pathway depends on:

Answer 18

Transfer efficiencies

Question 19

What is consumption efficiency (CE)?

Answer 19

It is the % of total productivity that is available at one trophic level that is consumed by the above trophic level

Question 20

What is assimilation efficiency (AE)?

Answer 20

It is the % of food energy taken into the guts of the consumers in that trophic level that is assimilated across the gut wall and becomes available for incorporation into or to do other work

Question 21

What is production efficiency (PE)?

Answer 21

It is the % of assimilated energy incorporated into new biomass; the remainder is entirely lost to the community as respiratory heat

Question 22

What is the overall trophic transfer efficiency?

Answer 22

It is CEAEPE and represents the % of energy or OM at one trophic level that is transferred to the next. Roughly 10% energy passed onto each level.

Look at drawing and efficiencies in slides!

Question 23

What is immobilization?

Answer 23

It occurs when an inorganic element is incorporated into organic form (often during PP)

ex. CO2 incorporated into plants carbohydrates

Question 24

What is decomposition?

Answer 24

It is the gradual disintegration of dead OM (bodies, feces, etc.) and is brought about by both physical and biological agencies. It includes the release of energy and mineralization of chemical nutrients

Question 25

What is mineralization?

Answer 25

It is the conversion of elements from organic back to inorganic form

Question 26

What are microbivores?

Answer 26

They are a group of animals that operates alongside detritivores and can be difficult to distinguish from them as they are minute animals that specialize at feeding on bacteria/fungi, but are able to exclude detritus from their guts

Question 27

What are shredders?

Answer 27

They are detritivores that feed on coarse particulate OM, such as tree leaves fallen into a river, because they fragment material into finer particles

Question 28

What are collector-filterers?

Answer 28

They consume fine particulate OM that would otherwise be carried downstream.

ex. river black fly larvae

Question 29

What do detritivores rely on to break down cellulose?

Answer 29

They rely on the production of cellulase enzymes by associated bacteria/fungi and protozoa

Question 30

What is the nitrogen cycle?

Answer 30

It is the continuing transformations of nitrogen, including biomass assimilation and ammonium mineralization

Question 31

What is nitrogen fixation?

Answer 31

It often occurs for plants through symbionts that convert N2 into NH4 (a useable form)

Question 32

What is denitrification?

Answer 32

It is when other bacteria are constantly converting nitrate into molecular N2 and mostly occurs in anaerobic environments

Question 33

What is nitrification?

Answer 33

It is when other bacteria convert ammonium to nitrate (for autotrophs to fix CO2)

Question 34

How can ecosystems be characterized by their openness/closedness?

Answer 34

By comparing their exchange of limiting nutrients across a border with the rate of recycling in an ecosystem.

ex. subtropical gyre is tightly closed because lots of recycling occurs and very few new N & P atoms enter surface water (assimilation by phytoplankton during NPP)
ex 2. heavily fertilized agricultural field has high rates of water exchange with adjacent estuaries, so the external supply of N may exceed the rate of recycling, making it open

Question 35

What is weathering?

Answer 35

It is when the parent bedrock or soil is broken down over time by the weather conditions, which is often the main nutrient source in many terrestrial ecosystems (taken up by roots)

Question 36

What is atmospheric deposition?

Answer 36

It is the net flux of materials from the atmosphere to an ecosystem. It is a major input source and is substantial in ecosystems with old weathered soils

Question 37

What is the first law of thermodynamics?

Answer 37

Conservation of matter & energy: Energy can be transformed but not created nor destroyed

Question 38

What is the second law of thermodynamics?

Answer 38

Entropy: Entropy is random, unavailable energy and disorder is always increasing

Converting energy causes an entropy tax b/c nothing is 100% efficient