Energy transfers and nutrient cycles

Question 1

Define biomass and give examples of fresh mass and dry mass

Answer 1

the mass of carbon or dry mass of tissue per given.
Examples of fresh mass: living, easy to access, variable water content, unreliable due to varying water content, variable food ingested
examples of dry mass: dead, difficult to assess, small sample size. may not be representative, unreliable as unethical to collect large samples, measured as gm-2 or gm-3, situational, only valid at that moment in time. standing crop may fluctuate

Question 2

Calculating energy stored in biomass

Answer 2

estimated using calorimetry.
Sample of dry biomass is combusted within a sealed chamber. The chamber is surrounded by a water bath and the heat energy released causes a temperature rise in the water. using the known specific heat capacity of water, and the volume of water and the temperature rise we can calculate the energy released from the mass of burnt biomass in kjkg-1

Question 3

energy transferred from sun to producer

Answer 3

1. some of the light is reflected by ozone layer
2. some light may not be absorbed by gases and vapour in the atmosphere
3. some of the light energy is the wrong wavelength
4. some light energy does not strike chlorophyll

Question 4

chemical energy and its equation

Answer 4

light energy is converted to chemical energy in the form of organic molecules (glucose amino acids dna etc)
GPP- chemical energy store in plant biomass in a given area or volume (rate of conversion of light energy into chemical energy of organic molecules by photosynthesis
NPP- chemical energy store in plant biomass after reparatory losses to the environment

NPP= GPP-R
available for plant growth, plant reproduction, other trophic levels

Question 5

producer to primary consumer

Answer 5

1. large amounts of the plant may be indigestible and lost from the animal in egested faeces
2. not all the plant may be eaten
3. some energy lost in excretion such as urine
4. energy lost in respiration and as heat to the envrionment

Question 6

photosynthetic efficiency equation

Answer 6

total light energy falling on the plant x 100

Question 7

How to calculate net production of consumers

Answer 7

N= I-(F+R)
I= chemical energy store of ingested food
F= the energy lost in faeces and urine
R= the energy lost in respiration

Question 8

primary to second consumer

Answer 8

1. large amounts of animal may be indigestible
2. not all of animal can be eaten
3. some energy lost in excretion
4. energy lost in respiration and and heat to environment
5. only energy that is stored as new biomass is available to the next trophic level

Question 9

percentage efficiency

Answer 9

energy available before transfer x 100

Question 10

yield can be determined by measuring the dry mass of plants
suggest how you could determine the dry mass of a sample of plant material

Answer 10

heat at 100ºc to evaporate water
weigh and reheat until no further change in mass

Question 11

what is the advantage of using dry mass and not fresh mass to compare the yield of plants

Answer 11

water content is variable
will not affect dry mass

Question 12

how can energy conversion rate be increased

Answer 12

restricting movement so less respiratory loss due to less muscle contraction
keeping animals indoors and warm to reduce heat loss from body
feeding nutritious- optimum type for growth eg with macro-nutrients
food source easier to absorb reducing energy lost in egestion
selective breeding- some varieties of breeds are more efficient at converting energy into new tissue
slaughtered before reaching adulthood so more energy transferred to biomass

Question 13

Process of the nitrogen cycle and the microorganisms it contains

Answer 13

Nitrification: Nitrifying bacteria. Ammonia to nitrates, nitrites to nitrates

Denitrification- denitrifying bacteria. Nitrates to nitrogen gas, also nitrates back to nitrites

nitrogen fixation: nitrogen fixing bacteria- nitrogen gas to ammonia

decomposition/ ammonification- nitrogen containing compound to ammonia by saprobiants.

Question 14

What molecules is nitrogen molecules

Answer 14

Amino acids, proteins, nucleic acids , ADP, ATP, NADP, NAD and FAD

Question 15

Nitrogen cycle

Answer 15

1. plants take up nitrogen from the soil in the form of NO3- which are absorbed by active transport through root hair cells
2. plant uses nitrogen to synthesise amino acids and proteins
3. consumers then eat plants and hydrolyse proteins into amino acids, these are absorbed and assimilated into new tissue
4. primary consumers may be eaten by secondary consumers and nitrogen passes up through trophic levels.
5. both plants and animals die
6. animals also excrete nitrogenous waste
7. decomposers, saprobiants, secrete extra cellular enzymes through exocytosis
8. this hydrolyses N containing polymers into monomers and release ammonia into soil- ammonification
9. ammonia oxidised to nitrites then nitrates by nitrifying bacteria- nitrification
10. nitrates converted to N2 gas by denitryfying bacteria- denitrification
11. nitrogen fixing bacteria can be found in the root nodules of some leguminous plants and rduce N2 gas to ammonia- nitrogen fixation

Question 16

how does electrical fixation occur

Answer 16

lightning

Question 17

describe how the action of microorganisms in the soil produces a source of nitrates for crop plants

Answer 17

1. protein converted into ammonia
2. by saprobiants
3. ammonia into nitrite
4. then nitrite to nitrate
5. by nitrifying bacteria
6. nitrogen gas to ammonia
7. by nitrogen fixing bacteria in the soil.

Question 18

phosphorous cycle

Answer 18

1. phospholipids, RNA and DNA from dead organisms into phosphate ions
2. decomposed by saprobionts
3. phosphate ions also found in waste and remains
4. phosphate ions transported by streams, rivers lakes and oceans
5. form sedimentary rock
6. weathering and erosion of rocks helps phosphate ions dissolve in oceans, lakes and soils
7. phosphate becomes available for absorption by plants to incorporate into biomass

Question 19

the role of mycorrhizae in nutrient cycles

Answer 19

increase total surface area of plants roots
increase the absorption of water
increase the absorption of mineral ions for example phosphates and nitrates
relationship is mutualistic, symbiotic. fungus will receive organic molecules from the plant such as sucrose and amino acids

Question 20

Two types of fertilisers

Answer 20

natural- waste materials such as manure
Artificial- manufactured, man-made powders or pellets produced in factories containing nitrates, phosphates and potassium ions

Question 21

environmental impact of fertilisers

Answer 21

reduced species diversity: plants which are adapted to soils with a high nitrate conc outcompete other species
environmental issues: crops are removed and less composition so less nitrate returned to the soil
leaching- result in more ions applied to the soil than taken up by the plant do ions dissolve in water and are washed from the soil into streams.

Question 22

eutrophication/leaching

Answer 22

nitrates washed away into water courses and builds up
high concentration of ions causes rapid growth of algal bloom
algae block light and less light penetrates the water meaning less photosynthesis
algae die
plants that can’t photosynthesise under water also die off
large increase in population of saprobiants
respiration rate increases
bacteria reduce oxygen concentration of water
oxygen levels depleted resulting in death of other aerobic organisms
increase in anaerobic respiration leads to release of toxins= putrid conditions

Question 23

Fluctuations in CO2 levels

Answer 23

CO2 will fluctuate according to the balance between photosynthesis and respiration.
Photosynthesis does not occur at night, plants still respire and therefore the CO2 at canopy height will be higher during the day
when photosynthesis is taking place during the day and the rate of photosynthesis exceeds the rate of respiration, the levels of CO2 at crop height will fall

Question 24

Measuring CO2

Answer 24

If done at ground level where there is less photosynthesis, then Co2 levels are higher
Air movement also effects levels of CO2- little air movement means an accumulation of CO2 can build up at night around the stomata of leaves
Winter- cooler temp and shorter days- reducion of photosynthesis. Less CO2 fixed and removed from atmosphere. Respiration occurs