Energy and Ecosystems

Question 1

define trophic level

Answer 1

stages in the food chain

Question 2

define biomass

Answer 2

total mass of living material in a specific area at a given time

Question 3

define food chain

Answer 3

feeding relationships

Question 4

define food web

Answer 4

many food chains linked together

Question 5

define saprobionts

Answer 5

decomposers that break down DOM to form simple molecules from complex ones

Question 6

define producer

Answer 6

photosynthetic organisms which synthesise organic substances from light, H2O, CO2

Question 7

define consumer

Answer 7

organisms that obtain energy by consuming other organisms

Question 8

define primary consumer

Answer 8

directly eats consumers

Question 9

define secondary and tertiary consumer

Answer 9

sec = eat primary consumer 
tert = eat secondary consumer

Question 10

most sugars synthesised by plants are used as…

Answer 10

respiratory substrates

Question 11

other sugars synthesised by plants make up biological molecules which form…

Answer 11

the biomass of the plant

Question 12

biomass can be measured in terms of mass of _____ or dry mass of _____ per given ____.

Answer 12

carbon, tissue, area

Question 13

how can the chemical energy stores in dry biomass be estimated?

Answer 13

calorimetry

Question 14

in any ecosystem, plants synthesise organic compounds from….

Answer 14

atmospheric or aquatic CO2

Question 15

define the 4 steps of calorimetry

Answer 15

1. sample dried in oven (evap H2O)
2. sample weighed + placed in the bomb + ignited in O2 atmosphere
3. heat from combustion transferred to H2O = thermometer increases in temp
4. can calculate energy content

Question 16

what is calorimetry

Answer 16

used to estimate the energy contained in a substance by measuring the heat generated during its combustion

Question 17

what 2 things you should note about the stirrer during calorimetry

Answer 17

1. stirrer increases accuracy = makes sure heat passes thru evenly
2. use plastic one = so doesn’t absorb heat

Question 18

when do you stop drying the sample?

Answer 18

until a constant mass is reached

Question 19

what is the formula for energy content of sampler?

Answer 19

4.2 x vol of H2O x temp change / mass of sample

Question 20

name 3 reasons why only 1-3% of Sun’s energy converted to OM

Answer 20

1. 90% sun rays reflected by clouds or absorbed by atmo.
2. not all wavelengths can be absorbed
3. light not fall on chloroplast

Question 21

name 4 reasons why energy is lost between trophic levels

Answer 21

1. parts of organism not consumed
2. excretory products i.e. urine
3. can’t be digested, lost in faeces
4. losses thru respiration

Question 22

why is there only 4/5 trophic levels?

Answer 22

insufficient energy is available to support a large enough breeding pop.

Question 23

define gross primary production (GPP)

Answer 23

chemical energy store in plant biomass in a given area/volume in a given time

Question 24

plants use around 20-50% of gross ______ ________ in _________ losses (R).

Answer 24

primary production, respiratory

Question 25

define net primary production (NPP)

Answer 25

chemical energy store in plant biomass after respiratory losses to the environment are taken into account

Question 26

what is the formula for NPP

Answer 26

NPP = GPP - R

Question 27

NPP is available to for what 2 things?

Answer 27

growth and reproduction

Question 28

NPP is available to other ______ levels in the ecosystem i.e. herbivores and _________

Answer 28

trophic, decomposers

Question 29

how is the net production of consumers (N) calculated?

Answer 29

N = I (F + R)

Question 30

what do these mean in the formula: I, F and R

Answer 30

``` I = chemical energy store of ingested food F = energy lost in faeces/urine R = energy lost in respiration ```

Question 31

what is the formula for calculating the % efficiency of energy transfers

Answer 31

energy available AFTER transfer / energy available BEFORE transfer x 100

Question 32

name 3 ways farming practices have been designed to increase efficiency of energy transfer

Answer 32

1. simplifying food webs = reduces energy losses to non-human food chains 2. restricting movement of animals i.e. in cages (less resp) 3. environment heated (reduces heat loss)

Question 33

name the 3 main features of nutrient cycles

Answer 33

- flow of nutrients is cyclic not linear - saprobiontic organisms release nutrients for reuse - nutrients recycled in ecosystems

Question 34

why is phosphorus important (3 reasons)

Answer 34

- DNA/RNA phosphodiester backbone (strengthens DNA) - ATP 3 phosphates (stores/releases energy) - phospholipid bilayer (allows lipid soluble molecules thu)

Question 35

which is slower: nitrogen or phosphorus cycle and why?

Answer 35

phosphorus as main reservoir is minerals as there is no air component

Question 36

describe the phosphorus cycle in 6 steps

Answer 36

1. phosphorus as phosphate (PO4^3-) in sedimentary rock deposits brought to surface by geological uplifting 2. weathering/erosion = phosphates dissolve 3. absorbed by plants 4. absorbed by animals 5. excess phosphate excreted + accumulates (guano) 6. death of organisms = saprobionts release phosphorus

Question 37

name the 2 reasons why nitrogen is important

Answer 37

- makes up amino acids/proteins | - makes up nucleic acids

Question 38

what is nitrogen fixation

Answer 38

when atmospheric nitrogen is converted into nitrogen containing compound in the soil

Question 39

name the 2 types of fixation

Answer 39

- biological | - industrial (Haber process)

Question 40

biological fixation is catalysed by __________ and is ________

Answer 40

nitrogenase, anaerobic

Question 41

nitrogen fixating bacteria respires....

Answer 41

aerobically

Question 42

role of free living bacteria in nitrogen fixation

Answer 42

- reduces gaseous nitrogen to ammonia | - nitrogen rich compounds released when they decay

Question 43

role of mutualistic bacteria in nitrogen fixation

Answer 43

live in root nodules of legumes (obtain carbohydrates from plant and plant acquires amino acids from them)

Question 44

what is ammonification

Answer 44

production of ammonia (NH3) from ammonium (NH4) | - saprobiontic organisms carry it out

Question 45

what is nitrification

Answer 45

ammonia oxidised into nitrite then oxidised into nitrate which plants can absorb by active transport

Question 46

what is denitrification

Answer 46

- converts soil nitrates into gaseous nitrogen | - occurs when soil is anaerobic i.e. waterlogged

Question 47

what mycorrhizae

Answer 47

a type of fungi that has a symbiotic relationship with the plant and assists in the uptake of H2O and inorganic ions

Question 48

what is the role of hyphae on mycorrhizae?

Answer 48

increase SA for H2O = mineral uptake

Question 49

why do we use fertilisers? (2)

Answer 49

- replace nitrates/phosphates lost by harvesting plants/ removing livestock - increases crop yield/productivity

Question 50

what are organic fertilisers

Answer 50

- made up of DOM, decaying OM or organic waste - add OM to soil = reduce erosion + hold H2O - release nutrients over long period of time

Question 51

what are inorganic fertilisers

Answer 51

- mined from rocks/deposits | - enriched in nitrogen/phosphorus/potassium

Question 52

name 2 advantages of inorganic fertilisers

Answer 52

- guaranteed composition (determine rates of application/ effect on crop) - concentrated = smaller amounts applied so reduces transport costs

Question 53

name the 3 main environmental effects of nitrogen containing fertilisers

Answer 53

- reduces biodiversity - leaching - eutrophication

Question 54

describe leaching

Answer 54

nitrates become soluble in rainwater and is carried out of soil. can lead to water pollution and eutrophication

Question 55

describe the process of eutrophication in 6 steps

Answer 55

1. algal bloom (increase cell division) = block light 2. photosynthetic plants die = reduce O2 3. increase decomposition = saprobionts use O2 4. less O2 = animals die 5. anaerobic saprobionts decompose DOM 6. release toxic substances = H2O putrid