energy transfers and the nutrient cycle

Question 1

what is an ecosystem

Answer 1

an ecosystem is a form of biological community containing all living and non-living factors

Question 2

what do all organisms require

Answer 2

all living organisms require energy to live for various processes e.g. some organisms obtain energy from the sun (plants) and some from consuming other organisms

Question 3

what is organisms use energy for

Answer 3

energy is used (and CO2) to synthesise organic compounds

e.g. in plants most sugars synthesised by plants are used as respiratory substances, the rest are used to form other biological molecules e.g. lipids

These molecules form the biomass

Question 4

how is biomass measured

Answer 4

it is measured in terms of carbon or dry mass of tissue per given area

Or
chemical energy store in dry biomass which is measured using calorimetry.

Question 5

how does calorimetry work

Answer 5

chemical energy store in dry biomass which is measured using calorimetry.

The amount of heat given off tells you how much energy is in it. Energy is measured in joules (J) or kilojoules (kJ).
A sample of dry biomass is burnt and the energy is used to heat to heat a known volume of water.
The change in temperature is used to calculate the chemical energy of the dry biomass

Question 6

what do food chains consist of

Answer 6

food chains consists of many trophic levels

Question 7

how does energy pass through food chains

Answer 7

energy is transferred throughout these trophic levels

Energy is lost throughout the food chain through process like respiration, excretion of faeces and urine

Question 8

how do we work out energy efficiency

Answer 8

net production of trophic level / net production of previous trophic level x 100

Question 9

how do we measure energy loss

Answer 9

net primary production (NPP)

net production

Question 10

how do we measure energy loss in plants

Answer 10

NPP = GPP-R

is is mainly used for plant forwth an reproduction because it does not take into accoint energy losses due to excretion and urine.
However it is available for herbivores and decomposes as they mainly obtain their energy via producers

Question 11

what is GPP

Answer 11

we can use via gross production (GPP) which is the chemical energy store in PLANTS’ biomass, in a given area or volume

Question 12

what is NPP

Answer 12

After knowing the GPP we can measure the NPP (net primary production)
which is the chemcial energy store in plant biomass AFTER RESPIRATORY LOSSES to the environment

Question 13

what is net production

Answer 13

net production is used for consumers higher up the tropic level

we use this equation: N = I -(F+R)

I= Chemical energy store in injested food

F= Chemical energy lost to the environment in faeces and urine

R= respiriroy losses to the environment

Question 14

how do we measure the RATE of primary and secondary production can be measured

Answer 14

the rate of primary/ secondary production is called primary/ secondary PRODUCTIVITY

This measured as biomass in a given area per time
it is a good way to measure primary and secondary production as it often changes with seasons

Question 15

why are nutrients important

Answer 15

nutrients are recycled within natural ecosystems in order to build important organic materials e.g. DNA

Question 16

what microoganisms recycle chemical elements

Answer 16

the main microorganisms are saprobiants

saprobiants are organisms that digest their food EXTERNALLY and then ABSORB THE PRODUCTS

e,g, fungi

Question 17

what are mycorrhizzae

Answer 17

they are fungal “associations” or a connection between plant roots and fungi

Mycorrhizae provide a large surface area for the uptake of water and inorganic ions

They act like a sponge so they can absorb and absorb and hold water and minerals

Question 18

what is the relationship between plants and fungi

Answer 18

the relationship between plants and fungi are mutualistic/ symbiotic
as the plant provides the fungi with carbohydrates while the fungi provides the plant inorganic ions/ water

Question 19

what are the stages of the nitrogen cycle

Answer 19

1. nitrogen - fixation
2. ammonification
3. nitrification
4. denitrification

Question 20

what happens in nitrogen fixation

Answer 20

1. nitrogen fixing bacteria converts atmospheric nitrogen to ammonium ions

the nitrogen fixing bacteria are either free - living in the soil or have a mutualistic relationship with legumious plants e.g. clovers and beans as they can live in their ROOT NODULES

Question 21

what is ammonification

Answer 21

1. ammonium ions in ammonification are produced from organic nitrogen e.g. decomposition of proteins, DNA, urea e.t.c are converted to ammonium ions which are released into the soil
2. this is carried out by saprrobiants: bacteria and fungi that can digest waste externally

Question 22

what happens in nitrification

Answer 22

1. ammonium ions in the soil (produced via ammonification and nitrogen fixation) are oxidised to nitrites then nitrates by nitrifying bacteria

this is a two stage oxidation reaction

Question 23

what happens in denitrification

Answer 23

1. it converts nitrogen in compounds back to nitrogen gas
2. denitrification is not a useful process as nitrogen gas cannot be absorbed by plants

It is carried out by Anaerobic denitrifying bacteria which iswh farmers aerate their soil so denitrification is limited

Question 24

what happens in the phosphorus cycle

Answer 24

1. environmental conditions e.g. erosion and weathering causes the release of phosphate ions by rocks into soil and bodies of water
2. plants assimilate (take in) these phosphate ions the phosphate ions are used by plants to sythesise DNA e.t.c
3. animals eat the plants and use the ions to sythesise organic materials
4. animals die and decompose returining the phosphate to the soil
5. bacteria (sapriobiants) in the soul break down phosphate into inorganic form (mineralisation)
6. inorganic forms of phosphorus can end up in water via rainfall again and be assimilated by plants

Question 25

what are fertillisers

Answer 25

fertilisers replace the nitrates and phosphates lost by harvesting plants and removing livestock

there are two types of fertilisers:
-natural

-artificial

Question 26

what are the advantages of natural fertilisers

Answer 26

1. cheaper and free if it comes from your own livestock

Question 27

what are the advantages of artificial fertilisers

Answer 27

1. contains the exact amount of minerals

2. more water-soluble so high absorption of inorganic ions

Question 28

what are the disadvantages of using artificial fertilizers

Answer 28

it can lead to leaching and eutrophication

Question 29

what is leaching

Answer 29

leaching is when water-soluble compounds are washed away into bodies of water
e.g. rivers and ponds

Question 30

what is the process of eutrophication

Answer 30

1. leached nitrates in bodies of water cause algae growth on the surface
2. excess algae growth blocks light, so plants the surface can’t photosynthesise and therefore die
3. aerobic bacteria feed on plant matter and response, using the O2 up in the water
4. Fish and other aquatic organisms die due to lack of O2