Energy transfers

Question 1

trophic level

Answer 1

the position an organism occurs within an energy transfer

Question 2

producers

Answer 2

-start of the food chain
-autotrophic meaning they make their own foods
-build up organic compounds from simple molecules needed for growth
-photosynthetic organisms build up complex organic compounds in the process of photosynthesis

Question 3

Consumers

Answer 3

-heterotrophic
-rely on external source of organic compounds
-animals are consumers

Question 4

saprobionts

Answer 4

-heterotrophic/saprotrophic
break down complex organic compounds in dead organisms
-eg. bacteria and fungi

Question 5

how saprobionts break down complex organic compounds

Answer 5

• secrete extracellular enzymes
  -hydrolyse organic material on outside of organism
  -absorb the hydrolysed monomer across cell membrane

Question 6

how many trophic levels in a food web

Answer 6

there are usually only 4-5 trophic levels in a food web as energy is lost each trophic level

Question 7

biomass

Answer 7

total mass of organic material in a specific area at a given time.

Question 8

fresh mass

Answer 8

-living
-easy to assess
-variable water content
-unreliable due to varying water content
-variable food indigested

Question 9

dry mass

Answer 9

-dead
-difficult to assess
-small sample size
-may not be representative
-unreliable as unethical to collect large samples
-gm-2
-situational as only valid at that moment in time standing crop as may fluctuate

Question 10

calculating energy in biomass

Answer 10

-calorimetry
-dry biomass is combusted with a sealed chamber
-chamber is surrounded by a water bath and heat energy released causes a temperature rise in the water
-using the known specific heat capacity of water and the volume of water and temp rise we can calculate energy released

Question 11

energy released equation

Answer 11

q=mc(change in t)

q/1000 = x

x/n = energy released

Question 12

how much sun energy is trapped in photosynthesis

Answer 12

only 1-3% of sun energy is trapped in photosynthesis

Question 13

energy loses from sun

Answer 13

-some of the light is reflected
-some light may be absorbed by gases/water vapour in the atmosphere
-some of the light is the wrong wavelength
-some light does not strike chlorophyll

Question 14

Gross primary production (GPP)

Answer 14

-light energy converted into organic molecules
-eg cellulose/starch

Question 15

Net primary production (NPP)

Answer 15

GPP-R

r=respiratory losses

Question 16

energy losses in food chain

Answer 16

-large amounts of the plant/animal may be indigestible
-lost from the animal as faeces.
-not all of the plant/animal may be eaten
-some energy is lost in excretion such as energy lost in urine
-energy lost in respiration and as heat to the environment

Question 17

net production of consumers can be calculated as

Answer 17

N= I - (F+R)

N= net production
I= chemical energy store
F= energy lost in faeces and urine
R= energy lost in respiration

Question 18

percentage efficiency

Answer 18

percentage efficiency= energy available after transfer/energy available before transfer x100

Question 19

Suggest how you could determine the dry mass of a sample of plant material

Answer 19

-heat at 100 to evaporate water
-weigh and heat and record then repeat until no further change in mass

Question 20

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

Answer 20

-water content is variable;
-will not affect dry mass

Question 21

Domestic livestock

Answer 21

-domestic livestock to increase productivity by reducing energy losses
-more energy is transferred into new tissue

Question 22

energy conversion rates is increased by

Answer 22

-restricting movement SO less respiratory loss due to less muscle contraction
-keeping warm SO reduced heat loss from body
-feeding nutritious foods SO optimum foods for growth
-food sources which are easier to digest reducing energy lost in egestion
-selective breeding animals which are more efficient at converting energy into new tissue which are genetically selected for high productivity
-slaughtered before reaching adulthood where least amount of respiration so more energy transferred to biomass

Question 23

monoculture definition

Answer 23

one particular crop grown over very large areas

Question 24

monoculture disadvantages

Answer 24

-very easy for disease to spread
-easy for insects to travel from plant to plant
-can e affected in a short space of time
-dramatically reduce biodiversity through loss of niches and a reduction in a variety of food sources

Question 25

chemical pesticides definition

Answer 25

general term given to chemicals used in the control of pests

Question 26

nutrient cycle

Answer 26

organic compounds in producers –> organic compounds in primary consumers –> organic compounds in secondary consumers –> decomposers –> organic compounds in producers

Question 27

the nitrogen cycle

Answer 27

nitrogen fixation –> nitrification –> assimilation –> ammonification

Question 28

nitrogen fixation

Answer 28

nitrogen fixing bacteria
found in root nodules in legumes
turn nitrogen gas to ammonia

Question 29

nitrification

Answer 29

nitrifying bacteria
turns ammonia to nitrites to nitrates

Question 30

assimilation

Answer 30

nitrates are absorbed into plants by active transport through root hair cells
plants use N for amino acids/DNA allows the plant to grow and reproduce
consumers eat the plants and hydrolase proteins into amino acids assimilated into new tissue
primary consumers eaten by secondary consumers

Question 31

denitrifying bacteria

Answer 31

nitrates converted to N2 gas by denitrifying bacteria
only occurs in waterlogged anaerobic conditions

Question 32

ammonification

Answer 32

sabrobiants secrete extracellular enzymes through exocytosis
used to hydrolyse N containing polymers into monomers which can be absorbed and release ammonia into the soil

Question 33

Describe how the action of microorganisms in the soil produces a source of nitrates for crop plants (5)

Answer 33

1. amino acids converted into ammonium
2. By saprobionts
3. Ammonium into nitrite
4. Nitrite into nitrate
5. By nitrifying bacteria
6. Nitrogen gas to ammonium
7. By nitrogen-fixing bacteria in soil

Question 34

How could a farmer make farmland more fertile

Answer 34

-fertiliser
-legumes
-aerate the soil
-drain the soil

Question 35

Phosphorus containing molecules

Answer 35

ATP
Phospholipids
Nucleic acids

Question 36

Erosion

Answer 36

once the rock has been weakened and broken up by weathering it is ready for erosion
erosion happens when rocks and sediment are picked up and moved to another place by ice,water or wind or chemical erosion

Question 37

deposition

Answer 37

sediments, soil and rocks are added to a landform or land mass

Question 38

Phosphorous cycle

Answer 38

1. phospholipids, RNA and DNA from dead organisms into phosphate ions
2. decomposed by saprobionts
3. phosphate ions are also found in waste and remains eg. guano, bones and shells
4. phosphate ions are transported by streams,rivers and lake
5. form sedimentary rock
6. weathering and erosion of rocks help phosphate ions dissolve into oceans and lakes
7. phosphates become available for absorption by plants via active transport to incorporate into biomass

Question 39

fertilisers

Answer 39

ions lost in soil need to be replaced
fertilisers can do this
organic- manure
inorganic- manufactured ,man made powders or pellets

Question 40

Leaching

Answer 40

inorganic fertilisers result in more ions applied to soil then plant uptake
leads to leaching, ions dissolve in soil water and are washed from the soil into streams, rivers and lakes

Question 41

eutrophication

Answer 41

nitrates washed away into water
high conc of ions cause rapid growth of algae
algae block light and less light penetrate water
less photosynthesis
algae die
aquatic plants die
increase population of saprobionts
respiration rate increases
O2 conc in water decreases
O2 levels drop resulting in death of aerobic organisms
increase in anaerobic respiration leads to release of toxins

Question 42

Mycorrhizae

Answer 42

fungi have a symbiotic relationship between fungi and plants

Question 43

mycelium

Answer 43

thin hair like structures
increase the surface area for the fungi to fix nitrogen gas, absorb water and nutrients. In return the plant provides the fungus with carbohydrates (sucrose) formed in photosynthesis