Nutrient Cycles

Question 1

What is problem with combustion in carbon cycle

Answer 1

Combustion fossil fuels unbalances cycle

Question 2

How is deforestation problem in carbon cycle

Answer 2

It stops plants from dealing with extra co2 from combustion of fossil fuels

Less plants = less photosynthesis to remove co2 from atmosphere

Question 3

Describe role of saprobiotic organisms in the carbon cycle

Answer 3

They secrete enzymes onto dead organisms to break molecules into smaller ones
Molecules then absorbed by diffusion
This carbon released as co2 when decomposer respires

Question 4

What are the 2 important greenhouse gases

Answer 4

Co2 and methane

Question 5

How do greenhouse gases lead to global warming

Answer 5

Make atmosphere thicker so heat can’t escape

Heat close to earth’s surface so earth gets hotter

Question 6

When is methane produced

Answer 6

When micro organisms break down organic molecules

Question 7

How does climate change lead to loss of species

Answer 7

Affects the niches available in a community

Question 8

Explain why co2 concentration of the atmosphere is less on a summer’s day than on a winter’s day

Answer 8

Summer = more light + temperature = more photosynthesis

Question 9

How does nitrogen in atmosphere become ammonium-containing molecules

Answer 9

Only plants called legumes

They have mutualistic bacteria which can fix nitrogen

Question 10

How do nirate ions become ammonium-containing molecules

Answer 10

Absorbed by active transport

Question 11

How does nitrogen in the air become ammonium ions?

Answer 11

Nitrogen is fixated by free living bacteria

Question 12

How does ammonification occur

Answer 12

Saprobiotic feeders release ammonia which then forms ammonium ions in the soil

Question 13

How does denitrification occur

Answer 13

Only occurs in water logged soil where there’s lack of oxygen
As there’s more anerobic bacteria which converts soil nitrates into gaseous nitrogen

Question 14

How does nitrite (no-2) become nitrate (no-3)

Answer 14

Nitrification:

Oxidation occurs from O2 in air
Allowed to happen by free living aerobic bacteria in soil that is nitrifying bacteria

Question 15

How does ammonium ions become nitrite (no-2)

Answer 15

Nitrification:

Oxidation occurs from O2 in air
Allowed to happen by free living aerobic bacteria in soil that is nitrifying bacteria

Question 16

What is the first 2 stages in eutrophication

Answer 16

NO-3 is limiting factor

NO-3 is leached into water so no longer limiting factor so plants grow exponentially

Question 17

What are the eutrophication stages after NO-3 is leached into water

Answer 17

Algal bloom

Algae absorb all light so lower plants have none

Light becomes limiting factor for lower plants
So lower plants die

Question 18

What are the eutrophication stages after the lower plants die

Answer 18

Dead plants are no longer limiting factor for saprobiotic organisms which grow exponentially

Saprobiotic organismsuse O2 for respiration so less O2

O2 becomes limiting factor for aerobic organisms

Question 19

What are the eutrophication stages after O2 becomes the limiting factor for aerobic organisms

Answer 19

Lake life die so more NO-3

Less aerobic organisms so less competition for Anerobic organisms which grow exponentially

Question 20

What are the eutrophication stages after anaerobic organisms grow exponentially

Answer 20

Anaerobic organisms decompose their material so more NO-3 and toxic waste
Substance released at same time
Hydrogen sulphide produced
Water known as putrid

Question 21

Describe the carbon cycle

Answer 21

Co2 in air
Photosynthesis by plants
Plants consumed by animals
Plants + animals respire
Plants + animals die
Micro organisms respire

Extra = combustion fossil fuels

Question 22

What is organic/natural fertiliser

Answer 22

Dead and decaying remains of plants and animals and animal waste

Question 23

What is inorganic/artificial fertiliser

Answer 23

Mined rocks and deposits then converted into different forms and blends

Question 24

What does research show about fertilisers

Answer 24

A combination or organic and inorganic fertilisers leads to the greatest long-term increase in productivity

Question 25

Why are fertilisers needed in agricultural ecosystems

Answer 25

Crops are repeatedly grown on same area of land
Minerals taken up by crops aren’t returned as crop consumed away from land
Mineral ion levels in soil reduced
This limits rate of photosynthesis
Fertilisers used to replace mineral ions

Question 26

What are the effects of nitrogen fertilisers

Answer 26

Reduces species diversity
Leeching
Eutrophication

Question 27

How does nitrogen fertiliser reduce species diversity

Answer 27

Nitrogen rich soils favour the growth of rapid growing species (eg grass) which out-compete many other species

Question 28

What is leeching

Answer 28

Pollution of watercourses

Question 29

What causes eutrophication

Answer 29

Leeching of fertiliser into watercourses