2.3 Flows of Energy and Matter

Question 1

Nitrogen Cycle

Answer 1

In which atmospheric nitrogen is transformed into a form that can be readily assimilated by plants

Question 2

Nitrogen fixation

Answer 2

Process, involving nitrogen fixing bacteria, in which atmospheric nitrogen is transformed into ammonium ions. The bacteria are found in the nodules of leguminous plants.

Nitrogen can also be fixed by lightning (splits apart molecules where they combine with oxygen to form nitrate salts which make way into soil profile.

Question 2

Haber process

Answer 2

In which nitrogen gas is converted into useable forms (nitrates). Used industrially in the manufacture of fertilisers.

Question 3

Legume

Answer 3

A type (Family) of plant with pea-flowers and bean like pods (including peanuts, lupin, lentils and chickpeas), with nodules that contain bacteria that fix nitrogen.

Question 4

Nitrogen fixing bacteria

Answer 4

Found in root nodules on legumes and involved in the fixation of nitrogen from the atmosphere into ammonium.

Question 5

Nitrogen

Answer 5

Occurs as a diatomic gas in the atmosphere. Makes up 78% of the atmosphere.
As nitrate ion (NO3-) can be assimilated by plants for physiological processes (making of proteins and nucleic acids).

In terms of pollution, note “nitrogen” itself is not a pollutant, but “nitrates” are.

Question 6

Ammonium

Answer 6

NH4+ Intermediate phase in nitrogen cycle between nitrogen gas and nitrites/nitrates.

Distinct from ammonia (NH3). Don’t confuse them.

Question 7

Nodule

Answer 7

Knob like structures on the roots of leguminous plants made by nitrogen fixing bacteria

Question 8

Fertilizer

Answer 8

Substance added to a crop to stimulate faster growth.
Can contain combinations of nitrites, nitrates, phosphates, ammonium.

Question 9

Urea

Answer 9

Found in manure and compost (decaying organic matter). Natural source of ammonium in the nitrogen cycle. Often referred to as a “slow release” fertiliser.

Question 10

Nitrification

Answer 10

Transformation of ammonium ions into nitrites and then nitrates (in the presence of nitrifying bacteria), to a form in which they can be assimilated by plants.

Question 11

Nitrifying bacteria

Answer 11

Involved in the process of nitrification in which ammonium is transformed into nitrites and then nitrates for assimilation.

Question 12

Denitrifying bacteria

Answer 12

Involved in the process of denitrification in which soil-based nitrate ions are converted back into gaseous atmospheric nitrogen

Question 13

Denitrification

Answer 13

Process in which soil-based nitrate ions are converted back into gaseous atmospheric nitrogen (with the aide of denitrifying bacteria)

Question 14

Assimilation

Answer 14

The taking up of nutrients by plants through their roots for use in physiological (structure building) processes.

Question 15

Consumption

Answer 15

How animals (including humans) get the nutrients they require. Involves eating plant matter either directly or through the food chain and then digesting them before the nutrients are assimilated through the gut wall.

Question 16

Nitrite

Answer 16

NO2 ion. Intermediate phase between ammonium and nitrate during nitrification.

Question 17

Nitrate

Answer 17

NO3 ion. Assimilated by plants. Product of nitrification (in the presence of nitrifying bacteria).

Form water soluble salts.
Main component of some fertilizers.
Biodegrades in the environment but can be concentrated in aquatic systems following runoff events.

Question 18

Photosynthesis

Answer 18

Occurs in plants (in the presence of chlorophyll and sunlight). Coverts light energy into stored chemical energy. Water and carbon dioxide, transforms into glucose and oxygen.

Question 19

Source of energy in a food chain/food web

Answer 19

The Sun

Question 20

Respiration

Answer 20

Occurs in all living cells, creates energy for organisms.
Glucose and oxygen become carbon dioxide, water (and energy)

Question 21

Aerobic respiration vs anaerobic respiration

Answer 21

Aerobic is “in the presence of oxygen”, anaerobic is “in the absence of oxygen” and can produce toxic by products.

Question 22

Chemosynthesis

Answer 22

certain organisms (such as deep sea bacteria) makes their own food from simple compounds and does not require sunlight

Question 23

Biomass

Answer 23

the total mass of all living organisms in a given area or ecosystem at a given time, often measured in terms of dry weight to exclude water content

Question 24

Productivity

Answer 24

the rate at which energy is converted by photosynthetic producers into organic substances that can be used as food by consumers.

Question 25

Assimilation

Answer 25

process by which organisms integrate the digested nutrients from their food into their body tissues for growth, repair, and energy.

Question 26

Productivity vs Assimilation

Answer 26

Productivity measures the rate at which organisms produce organic matter. Assimilation involves the incorporation of this produced matter into the organisms’ tissues for growth and energy.

Question 27

GPP

Answer 27

Gross primary productivity.
The total rate at which an ecosystem’s producers, convert carbon dioxide into organic matter through photosynthesis, before any energy is used for respiration

Question 28

Gross productivity vs net productivity

Answer 28

Gross productivity refers to the total amount of energy or biomass produced by an ecosystem, whereas net productivity is the energy or biomass remaining after accounting for the energy used in respiration.

Question 29

NPP

Answer 29

Net primary productivity.
The difference between the energy captured through photosynthesis (gross primary productivity) and the energy expended through metabolic processes (respiration).
NPP = GPP-R

Question 30

GSP

Answer 30

Gross secondary productivity.
The total rate at which consumers, such as animals, in an ecosystem produce biomass through the assimilation of food, before accounting for losses due to respiration and other metabolic processes.
GSP = ingestion - egestion

Question 31

NSP

Answer 31

New secondary productivity.
The rate at which consumers in an ecosystem accumulate biomass, after subtracting the energy they expend on respiration and other metabolic activities from their gross secondary productivity.
NSP = GSP - R

Question 32

Egestion

Answer 32

Pooping!
Expulsion of undigested material from their digestive system, essentially the removal of waste products that cannot be absorbed as nutrients

Question 33

Ingestion

Answer 33

Food going in.
As opposed to “egestion” - food going out.

Question 34

Efficiency of productivity

Answer 34

The percentage of energy that is transferred from one trophic level to the next.
(net productivity x 100)/gross productivity

Question 35

Efficiency of assimilation

Answer 35

(Gross Productivity x100)/food eaten

Question 36

Units for productivity

Answer 36

units of energy or biomass produced per unit area per unit time
(eg grams of carbon per square metre per year)

Question 37

How to measure biomass

Answer 37

Harvesting the biological material within a sample, wash it and then dry it until it reaches a constant weight. The mass of this is called the “dry weight”. You can use this figure to extrapolate the total biomass of an ecosystem.
Modified to a measure called “above ground biomass” in which the roots are not part of the harvest.

Question 38

Measuring primary productivity (terrestrial plants)

Answer 38

Obtain dry biomass of a sample
With two other similar samples (in situ), cover one in black plastic, so it cannot photosynthesize, and leave the other one as is.
After a period of time, harvest the two patches from above and obtain dry weight.

Question 39

Measuring secondary productivity

Answer 39

weigh an organism, weigh how much it eats, and then weigh how much it egests. (Ingestion-egestion)

Question 40

Primary productivity vs secondary productivity

Answer 40

Primary = plants (producers)
Secondary = animals (consumers)

Question 41

Measuring primary productivity in aquatic ecosystems

Answer 41

Light-dark bottle method.
Two bottles of the same water. Oxygen content measured.
One bottle covered, so light cannot penetrate (no photosynthesis). After a period of time, measure oxygen content again.