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

carried out in a bomb calorimeter, in which a sample of known mass is burnt in pure oxygen.
the bomb calorimeter is submerged in water and therefore the change in water temperature can be used to calculate the energy in the sample

Question 11

define gross primary production

Answer 11

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

Question 12

define net primary production

Answer 12

the chemical energy store in plant biomass taking into account the energy that will be lost due to respiration (R)

Question 13

formula to calculate net primary production

Answer 13

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 14

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

Answer 14

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 15

what units are used to record rates of productivity

Answer 15

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 16

explain the reasons why a low % of energy is transferred between trophic levels

Answer 16

-some of the organism is not consumed
-some parts cannot be digested
-some energy is lost in excretory substances
-some energy lost from respiration, lost to the environment

Question 17

formula to calculate efficiency of energy transfer between trophic levels

Answer 17

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

Question 18

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

Answer 18

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 19

how is production affected by simplifying food webs

Answer 19

by simplifying food webs it aims to reduce energy losses to non-human food chains
e.g. reduce/eliminate organisms being farmed (crops compete with plants for water, space, light etc.)

Question 20

nitrogen cycle stages

Answer 20

ammonification
nitrification
denitrification
nitrogen fixation

Question 21

describe ammonification

Answer 21

this is the production of ammonia from organic nitrogen containing compounds.
-saprobiontic microorganisms feed on faeces and dead organism materials, releasing ammonia which then forms ammonium ions in the soil
-the nitrogen returns to the non living component of the ecosystem

Question 22

describe nitrification

Answer 22

oxidation reactions occur which release energy, and this is carried out by nitrifying bacteria:
-oxidation of ammonium ions into nitrite ions
-oxidation of nitrite ions into nitrate ions
the nitrifying bacteria needs oxygen for two reasons:
-to carry out aerobic respiration
-oxygen is used for these conversions

Question 23

why is it important for farmers to keep their soil structure light and well aerated

Answer 23

ensures that there is enough oxygen for nitrifying bacteria to carry out its function.
-ensures the plants get the nitrate they need

Question 24

describe dentrification

Answer 24

breakdown of nitrates into nitrogen gas, by nitrifying bacteria, which is released into the atmosphere

Question 25

describe nitrogen fixation

Answer 25

where nitrogen gas is fixed into other compounds by bacteria with a nitrogen fixing ability.
-do so by reducing nitrogen gas to ammonia which subsequently dissolves to form ammonium ions
-the relationship between nitrogen fixing bacteria and the plant is mutualistic as it is beneficial to both organisms

Question 26

where is nitrogen fixing bacteria found

Answer 26

root nodules of leguminous plants

Question 27

outline the phosphorus cycle

Answer 27

phosphorus exists mostly as phosphate ions in sedimentary rocks as a result of weathering.
the ions are then absorbed by plants and are incorporated into their biomass
animals obtain the ions when they feed on these plants
excess ions are excreted and may accumulate in waste material
decomposers break down these dead plants and animals which release phosphate ions into the water and soil
some of the ions are left in remains such as bone or shell, because it takes longer to decompose
the phosphate ions are then released by decomposition or dissolve out of rocks and are transported by rivers/streams into lakes/oceans where they form sedimentary rock and complete the cycle

Question 28

explain the role of mycorrhizae in nutrient cycles

Answer 28

fungi increase the SA for absorption of water/minerals.
it also acts as a sponge in the soil so holds water/minerals in the neighborhood of roots.
this increases drought resistance and take up inorganic ions more easily

Question 29

what is the relationship like between mycorrhizae and plants

Answer 29

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

Question 30

why does agriculture cause a loss in nutrients

Answer 30

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 31

why are fertilisers used

Answer 31

replaces the lost minerals and increases the energy efficiency of the food chain

Question 32

define natural fertilisers

Answer 32

organic matter such as manure, sewage sludge, seaweed etc

Question 33

define artificial fertilisers

Answer 33

inorganic material such as pure chemicals such as pure chemicals e.g. ammonium nitrate as powder/pellets

Question 34

environmental issues with fertilisers

Answer 34

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

Question 35

when is leaching more likely to occur and with which fertiliser

Answer 35

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

Question 36

why is natural fertiliser being less soluble a benefit

Answer 36

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 37

eutrophication

Answer 37

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.