energy flow

Question 1

biomass

Answer 1

the dry mass of organic molecules

Question 2

productivity

Answer 2

rate of biomass accumulation

Question 3

units if productivity

Answer 3

kg/km2/year

Question 4

net productivity of consumers

Answer 4

NP = I - (E+R)

net productivity = ingested - (egestion + respiratory losses)

Question 5

net productivity of producers

Answer 5

NPP = GPP - R

net primary productivity = rate of photosynthesis - respiratory losses

Question 6

% of light energy which becomes chemical energy in producers

Answer 6

2%

Question 7

% chemical energy in producers which becomes chemical energy in primary consumers

Answer 7

10%

Question 8

% chemical energy in primary consumers which becomes chemical energy in secondary consumers

Answer 8

20%

Question 9

why is percentage of chemical energy lost between trophic levels so high

Answer 9

• not all of previous trophic level is consumed or didgested
• energy lost in undigestible food (eg. feaces)
• respiratory losses of energy
• excretion - CO2/urea
• some of organism cannot be consumed

Question 10

why is percentage of chemical energy lost between sun and producers so high

Answer 10

• not all wavelengths of light are absorbed by pigments - some reflected
• some light reflected by clouds
• not all light hits chlorophyll
• limiting factors affect rate of photosynthesis

Question 11

how to increase productivity of producers (5)

Answer 11

• sewing density
• controlling pests
• fertilisers
• genetically modifying / selected breeding
• control limiting factors eg. temp, light + CO2

Question 12

how to increase productivity of consumers (non-producers) (8)

Answer 12

• restricting movement - limiting respiratory losses
• keep warm - limit heat lost to environment
• vaccination - reduce disease
• more digestible food
• selective breeding
• hormones/steroids
• more nutrient rich food
• early slaughter - when feed:gain ratio is at its highest

Question 13

percentage efficiency

Answer 13

energy available after transfer / energy available before transfer x 100

Question 14

advantages of artificial fertilisers

Answer 14

• faster response

- specific to a crop

Question 15

disadvantages of artificial fertilisers

Answer 15

• expensive (although less machinery needed)

- soluble - lead to leaching

Question 16

advantages of natural fertilisers

Answer 16

• free/cheap - eg. manure
• increases soil stability
• organic
• increases drainage - decrease water-logging

Question 17

disadvantages of natural fertilisers

Answer 17

• slower acting - as decomposition needed

Question 18

environmental consequences of overuse of fertilisers (2)

Answer 18

• loss of biodiversity - extra N spreads to neighbouring environments, favouring fast-growing plants ie. weeds which outcompete other species
• eutrophication

Question 19

detritus

Answer 19

dead organic matter

Question 20

saprobiotic bacteria

Answer 20

decomposers

Question 21

ammonification

Answer 21

converting nitrogen ion in detritus to ammonium ions in the soil

Question 22

nitrification

Answer 22

taking ammonium ions and

Question 23

producers

Answer 23

photosynthetic organisms which make organic substances using light energy, H2O and CO2 + mineral ions

Question 24

consumers

Answer 24

organisms which obtain energy by feeding on other organisms (p. s. t. )

Question 25

food chain

Answer 25

feeding relationship where producers are eaten by consumers - each stage is a TROPHIC LEVEL - diagram shows energy flow through ecosystem

Question 26

how to estimate energy store in dry mass - method - units of results

Answer 26

CALORIMETRY - bomb calorimetry - sample of dry material weighed and burnt in exc. O2 in sealed chamber - energy given out heats water and temp rises - calculate energy change in kJ/Kg

Question 27

d. Gross primary product (GPP)

Answer 27

total quantity of chemical energy in plant biomass in a given area/volume

Question 28

Net primary productivity (NPP)

Answer 28

chemical energy store after taking respiratory losses into account

Question 29

summary of nitrogen cycle:

Answer 29

1) AMMONIFICATION - saprobiotic bacteria make ammonia from dead organisms and waste -> ions into soil 2) NITRIFICATION - nitrifying bacteria make NO3- ions by oxidation reactions of ammonium ions -> nitrite ions -> nitrate ions 3) NITROGEN FIXATION - nitrogen gas - > nitrogen containing compounds - by: 1 - free living nitrogen fixing bacteria (make ammonia and release nitrogen rich compounds when they die and decay) 2 - mutualistic nitrogen fixing bacteria in nodules of plant roots - obtain carbs from plants and releases amino acids to plants 4) DENITRIFICATION - [less O2 = less aerobic nitrifying and nitrogen-fixing bacteria. more anaerobic denitrifying bacteria] - convert nitrates to gaseous N2 gas

Question 30

how to combat denitrification

Answer 30

keep soils well aerated and drained

Question 31

stores of phosphorus

Answer 31

mineral rock

Question 32

stores of nitrogen

Answer 32

gases in atmosphere

Question 33

eutrophication process

Answer 33

- lakes and rivers, [N] = limiting factors - [N] ↑ = algae +plant pop. ↑ - algal bloom at surface, reducing light intensities for plants at lower depths (= limiting factor) - plants die - broken down by saprobiotic bacteria - releasing CO2 by aerobic respiration - [O] ↓ = limiting reactant - fish and aerobic organisms die (broken down) - anaerobic pop ↑ more dead material to break down - releasing products such as nitrates and Hydrogen sulfates, making water putrid

Question 34

effects of nitrogen (neg.)

Answer 34

- leaching - down by rainwater out of reach of plants and into groundwater supplies - leading to health effects eg stomach cancers - reduced species diversity as high [N] favours fast growing plants - increased interspecific competition

Question 35

uses of phosphorus (3)

Answer 35

- ATP - Phospholipids - DNA

Question 36

uses of nitrogen (2)

Answer 36

- nucleic acid synthesis - ATP - amino acids