Energy Transfer and Nutrient Cycles

Question 1

Def; ecosystem

Answer 1

a biological community of interacting organisms and their physical environment.

Question 2

Def; biomass

Answer 2

the chemical energy stored in the plant

Question 3

Two techniques to measure biomass?

Answer 3

1) Dry mass is the mass of the organism with the water removed
A sample of the organism is dried in the oven set to a low temperature. The sample is then mweighed at regular intervals so when the mass is constant all the water has been removed.
2) Calorimetry
A sample of dry biomass is burnt and the enery realease is used to heat a known volumw of water. The change in temperature of the water is used to calculate the chemical energy of the biomass

Question 4

Def; Gross Primary Production (GPP)

Answer 4

The total amount of chemical energy converted from light energy by plants in a given area

Question 5

Def; Net Primary Production (NPP)

Answer 5

The energy available to the plant for growth and reproduction

Question 6

Def; Respiratory loss

Answer 6

the enery lost to the environment as heat when plants respire

Question 7

link NPP, GPP, R

Answer 7

NPP = GPP - R

Question 8

Formula: Net production (N)
(I) Chemical energy ingested in food
F (Chemical energy lost in faeces)
R (Energy lost through respiration)

Answer 8

N = I - (F + R)

Question 9

Def: decomposers

Answer 9

decomposers break down dead or undigested material, allowing nutrients to be recycled

Question 10

How to reduce energy loss? (via simplifying food webs)

Answer 10

Insecticides
Herbicides
Parasites
Pathogenic bacteria and viruses

Question 11

How to reduce energy loss? (via respiratory losses)

Answer 11

limit movement

keep pens indoor and keep warm

Question 12

Def; saprobionts

Answer 12

organisms that secrete enzymes and digest their food externally, then absorb the nutrients they need.

Question 13

Def; mycorrhizae

Answer 13

Some fungi form symbiotic relationships with the roots of plants.

Question 14

Def; hyphae

Answer 14

Fungi which are made of long thin strands which connect to plant roots. This increases the SA of the plant root system. In return the hyphae obtain organic compounds from the plant.

Question 15

Def; nitrogen fixation

Answer 15

when nitrogen gas in the atmosphere is turned into nitrogen-containing compounds.

Question 16

what carries out nitrogen fixation?

Answer 16

By bacteria (Rhizobium) that turns nitrogen into ammonia, which goes on to form ammonium ions in solution to be uptaken by plants.

Question 17

def; ammonification

Answer 17

when nitrogen compounds from dead organisms are turned into ammonia by sapriobionts, which goes on to form ammonium ions.

Question 18

def; nitrification

Answer 18

when ammonium ions in the soil are changed into nitrogen compounds that can then be used by plants.

Question 19

what carries out nitrification

Answer 19

Nitrifying bacteria (Nitrosomonas) change ammonium ions into nitrites. The other nitrifying bacteria called Nitrobacter change nitrites into nitrates.

Question 20

def; denitrification

Answer 20

when nitrates in the soil are converted into nitrogen gas by denitrifying bacteria - they use nitrates in the soil to carry out respiration and produce nitrogen gas.

Question 21

Explain the phosphorus cycle (4)

Answer 21

1) phosphate ions in rocks are released via weathering into the soil
2) phosphate ions are taken into the plants via the roots, mycorrhizae help the uptake.
3) phosphate ions are lost from animals via feces and are passed down the food chain when they eat each other.
4) when animals and plants die (and via feces), saprobionts are involved in breaking down the organic compounds, releasing phosphates.

Question 22

Def; guano

Answer 22

Waste produced by sea birds with a high proportion of phosphate ions

Question 23

process of eutrophication (5)

Answer 23

mineral ions leached from fertilized fields stimulate the rapid growth of algae in ponds and rivers.

2) large amounts of algae block light from reaching the plants below.
3) eventually the plants die because they’re unable to photosynthesise enough.
4) bacteria feed on the dead plant matter. The increased number of bacteria decreases the oxygen concentration.
5) fish and other aquatic animal die.