Unit 5: energy transfer in & between organisms

Question 1

define community

Answer 1

all the living organisms that live in a habitat at the same time

Question 2

define population

Answer 2

the number of the same species that live in a habitat at the same time

Question 3

define ecosystem

Answer 3

a community in conjunction with the non living components of the environment

Question 4

define abiotic

Answer 4

the non-living, chemical and physical components of the ecosystem

Question 5

define biomass

Answer 5

the total mass of living matter within an organism

Question 6

how can the amount of biomass remaining in an organism be measured

Answer 6

in terms of:
-mass of carbon
-dry mass of tissue per given area

Question 7

why is dry mass used instead of wet mass

Answer 7

wet mass can vary too much- unreliable results

Question 8

define calorimetry

Answer 8

a technique used to measure the quantity of heat gained/lost by a system

Question 9

what is calorimetry used for

Answer 9

to estimate the chemical energy store in dry biomass

Question 10

process of calorimetry

Answer 10

1. known mass of dry biomass is fully combusted
2. heat energy released heats a known volume of water
3. increase in temperature of water used to calculate chemical energy of biomass

Question 11

explain how features of a calorimeter enable valid measurement of heat energy released

Answer 11

1. stirrer- evenly distributes heat energy in water
2. air/insulation- reduces heat loss & gain to & from surroundings
3. water- has a high specific heat capacity

Question 12

define gross primary production

Answer 12

the chemical energy store in plant biomass, in a given area or volume
-it is the total energy resulting from photosynthesis

Question 13

define net primary production

Answer 13

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

Question 14

formula to calculate net primary production

Answer 14

NPP= GPP - R
NPP is the energy left over that is available to the plant to create new biomass and therefore available to the next trophic level in a food web

Question 15

formula to calculate the net production of consumers (N), such as animals

Answer 15

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

Question 16

what units are used to record rates of productivity

Answer 16

kJ ha-1 year-1
-kJ is unit for energy
-recorded as per unit area to standerdise the results to enable environments to be compared, takes into accounts different environments will vary ins size
-per year to take into account the impact seasons will have on rain, light and heat- provides an annual average to allow fair comparisons between environments

Question 17

explain why energy transfer between trophic levels is insufficient

Answer 17

-heat energy is lost via respiration
-energy lost via parts of organism that arent eaten (e.g. bones)
-energy lost via food not digested-lost as faeces
-energy lost via excretion e.g. urea in urine

Question 18

formula to calculate efficiency of energy transfer between trophic levels

Answer 18

percentage efficiency= (energy available after the transfer/energy available before the transfer) X 100

Question 19

example of how farmers are reducing respiratory losses within a human food chain and why this is important

Answer 19

importance- reduce energy loss and increase yield
e.g. keeping animals in confined spaces to reduce muscle movement and keep the, warm to reduce heat loss (ethical concerns)

Question 20

explain how crop farming practices increase energy transfer efficiency

Answer 20

1. simplifying food webs to reduce energy/biomass losses to non-human food chains e.g.
   -herbicides kill weeds-less competition so more energy to create biomass
   -pesticides kill insects-reduce loss of biomass from crops
   -fungicides reduce fungal infections-more energy to create biomass
2. fertilizers e.g. nitrates to prevent poor growth due to lack of nutrients

Question 21

explain the role of saprobionts in recycling chemical elements

Answer 21

-decompose organic compounds e.g. proteins, urea, DNA in dead matter by secreting enzymes for extracellular digestion. saprobionts absorb soluble needed nutrients and release mineral ions

Question 22

give examples of biological molecules that contain nitrogen

Answer 22

amino acids, proteins or enzymes, urea, DNA or RNA, ATP or ADP, NAD or NADP

Question 22

give examples of biological molecules that contain nit

Question 23

nitrogen cycle stages

Answer 23

ammonification
nitrification
denitrification
nitrogen fixation

Question 24

describe role of bacteria in nitrogen fixation

Answer 24

-nitrogen gas (N2) converted into ammonia (NH3) which forms ammonium ions (NH4+) in soil -by nitrogen fixing bacteria

Question 25

suggest why ploughing (aerating) soil increases its fertility

Answer 25

-more ammonium converted into nitrite and nitrate- more nitrification -less nitrate being converted into nitrogen gas-less denitrification

Question 26

describe role of bacteria denitrification

Answer 26

-nitrates in soil converted into nitrogen gas (reduction) -by denitrifying bacteria in anaerobic conditions (no oxygen, e.g. waterlogged soil)

Question 27

where is nitrogen fixing bacteria found

Answer 27

root nodules of leguminous plants

Question 28

outline the phosphorus cycle

Answer 28

1. phosphate ions in rocks are released by erosion/weathering 2. phosphate ions are taken up by producers/plants and incorporated into their biomass -rate of absorption is increased by mycorrhizae 3. phosphate ions transferred through food chain 4. some phosphate ions lost from animals in waste products 5. saprobionts decompose organic compounds, releasing phosphate ions

Question 29

explain the role of mycorrhizae in nutrient cycles

Answer 29

fungi acts as an extension of plant roots to increase surface area of the root system which increases the rate of uptake/ absorption of water and inorganic ions. in return, fungi receives organic compounds e.g. carbohydrates

Question 30

what is the relationship like between mycorrhizae and plants

Answer 30

mutualistic relationship -fungi gets sugars and amino acids from the plant -plant benefits from increased water/ion uptake

Question 31

why does agriculture cause a loss in nutrients

Answer 31

when crops are harvested, minerals are removed and not returned upon decomposition because the crops are taken away for consumption so minerals are not replaced by their remains/waste products

Question 32

why are fertilisers used

Answer 32

replaces the lost nitrates/phosphate's when plants are harvested and livestock are removed- those removed from the soil and incorporated into biomass cant be released back into the soil through decomposition by saprobionts so improves the energy efficiency of energy transfer

Question 33

define natural fertilisers

Answer 33

organic matter such as manure, sewage sludge, seaweed etc where ions are released during decomposition by saproobionts

Question 34

define artificial fertilisers

Answer 34

contain inorganic compounds of nitrogen, phosphorus and potassium

Question 35

environmental issues with fertilisers

Answer 35

when more fertiliser is added to soils, it can be leached into waterways by rain or irrigation. this leads to eutrophication.

Question 36

when is leaching more likely to occur and with which fertiliser

Answer 36

if the feriliser is applied just before rainfall -artificial fertiliser is more soluble soluble

Question 37

why is natural fertiliser being less soluble a benefit

Answer 37

the fertiliser is released slower and with more control (tends to just replace what has been taken) so it is harder to add in excess, therefore less leaching

Question 38

eutrophication

Answer 38

causes by excess nutrients leaching into the waterways. -provides algae in waterways with enough nitrate ions to grow more rapidly than it otherwise would do. as a result, this can block out light from other plants, causing decay and the use of oxygen in the water way. this eventually leads to the death of the ecosystem.