13: Energy and ecosystems

Question 1

Ecosystem

Answer 1

form of a biological community containing all living and non-living factors

Question 2

How is biomass measured

Answer 2

• mass of carbon or dry mass of tissue per given area OR
• chemical energy store in dry biomass with a calorimetry

Question 3

Food chain (the trophic levels)

Answer 3

• producer (produce own carbs)
• primary consumer
• secondary consumer
• tertiary consumer
  Energy from consuming, but lsot through excretion of faeces, urine and respiration

Question 4

Measuring energy loss

Answer 4

• Gross primary production (GPP) = the chemical energy store in a plant biomass, in given area or volume
• Net primary production = the chemical energy store in a plant biomass, after respiratory losses to the environment have been taken into account
  NPP = GPP - R

Question 5

Calculating net production in consumers

Answer 5

N = I- (F+R)
I is chemical energy store in ingested food
F is chemical energy lost from faeces and urine
R is respiratory

the n goes towards making the biomass

Question 6

Whats the rates of productivity recorded in

Answer 6

kJ, ha-1, year-1
- recorded per unit to standardise the results so environments can be compared. it takes into account environments vary in size
- per year as take into account the seasons

Question 7

Is the flow of energy through an ecosystem cyclical or linear

Answer 7

• linear. energy that enters as sunlight is lost as heat which cant be recycled

Question 8

Nutrient cycle process

Answer 8

• nutrient taken up by producers as inorganic molecules
• producer incorporates nutrient into complex organic molecules
• consumer eats producer and nutrients is passed on
• then passes along food chain
• when the producers and consumers die, the nutrients is broken down by saprobiontic microorganisms (decomposers) that release nutrients in simpliest form

Question 9

What % of the atmosphere is nitrogen

Answer 9

78%

Question 10

Which biological molecules contain nitrogen

Answer 10

proteins, atp and nucleic acids

Question 11

The importance of the nitrogen cycle

Answer 11

• microorganisms are needed to convert nitrogen gas into nitrogen containing substances that plants and animals can absorb
• nitrogen gas contains a triple bond

Question 12

Four main stages of the nitrogen cycle

Answer 12

1) ammonification
2) nitrification
3) nitrogen fixation
4) denitrification

Question 13

Stage 1 of nitrogen cycle

Answer 13

• ammonification
• ammonia is produced from nitrogen-containing compounds which include urea, proteins, nucleic acids and vitamins
• saprobiontic microorganisms feed on faeces and dead organisms materials and so release ammonium ions in soil

Question 14

Stage 2 of nitrogen cycle

Answer 14

• nitrification
• ammonium ions is converted to nitrate ions, oxidation reaction so releases energy
• carried out by free living soil microorganisms called nitrifying bacteria and conversion occurs in two stages. oxygens needed so farmers need to keep soil structure light by ploughing
• 1) oxidation of ammonium ions to nitrite ions
• 2) oxidation of nitrite ions to nitrate ions

Question 15

Stage 3 of the nitrogen cycle

Answer 15

• nitrogen fixation
• nitrogen gas is converted into nitrogen-containing compounds
• occurs industrially, and lightning passes through atmosphere
• its carried out by two main types of micro-organisms
  1) free-living nitrogen fixing bacteria (reduce gasesous nitrogen to ammonia, to manufacture amino acids)
  2) mutualistic nitrogen-fixing bacteria (live in nodules of the roots of plants such as beans and peas. they obtain carbs from plant, and collect amino acids from bacteria)

Question 16

Stage 4 of the nitrogen cycle

Answer 16

• denitrification
• soil becomes water logged and have low oxygen conc
• the type of microorganism present changes
• increase in anerobic denitrifying bacterica which convert soil nitrates into gaseous nitrogen
• reducing availability for nitrogen-containing compounds for plants

Question 17

The phosphorus cycle

Answer 17

• component of ATP, phospholipids and nucleic acids so essential element
• main reservoir is in mineral form in sedimentary rock

Question 18

Whats mycorrhizae in the phosphorus cycle

Answer 18

fungal associations between plant roots and beneficial fungi
- fungi acts as extensions of roots and increase sa for absoprtion of water and minerals which allows plant to better resist drought
- it improves the uptake of relatively scarce ions such as phosphate ions
- the mycorrhizae acts as sponge
- mutualistic relationship between plants and fungi. plant benefits from improved water and inorganic ion uptake. fungus receives organic compounds such as sugars and amino acids from plant

Question 19

The phosphorus cycle process

Answer 19

phosphate ions in soil and oceans are;
- absorped as phosphate ions in plants which are consumed by animals and then excreted back into soils and oceans
- this can also cause phosphate ions in wastes and remains which goes back to soils and oceans by erosion
- or it deposits as ‘phosphates in rock’ , can also be caused by sedimentation.
- this goes back to oceans and soils by erosion and the use of fertilisers

Question 20

Fertilisers

Answer 20

added to soil to replace the nitrate and phosphate ions lost when plants are harvested and removed from the nutrient cycles as crops

Question 21

Types of fertilisers

Answer 21

• natural (manure) cheaper but dont contain exact proportion of minerals you need
• artificial (inorganic soluble chemicals) have the exact proprtion of minerals that plants require, however they are soluble chemicals so can dissolve in rainwater and leach, so run off from rain water into nearby waterbodies

Question 22

Eutrophication

Answer 22

• when nitrate leached from fertilised fields stimulate growth of algae in a pond
• the excessive growth of algae creates a blanket on the surface of the water which blocks out sun
• so plants below blanket cant photosynthesis and die
• bacteria in the water feed and respire on the dead matter
• results in an increase of bacteria, which all respire so use up oxygen in the water
• fish and other aquatic organisms die due to lack of dissolved oxygen