Nutrient cycles

Question 1

What environmental factors may affect decomposition?

Answer 1

• water
• oxygen
• heat

Question 2

What do plants need nitrogen for?

Answer 2

The synthesis of proteins and other compounds, including DNA and vitamins.

Question 3

Despite nitrogen gas making up 80% of the earth’s atmosphere, plants can’t actually get it into themselves in it’s direct nitrogen form. What must they absorb it as instead?

Answer 3

Nitrate

Question 4

What two processes form nitrate?

Answer 4

Nitrogen fixation and nitrification

Question 5

What is the average water temperature found over the Earth’s surface?

Answer 5

16.5 *C

Question 6

What are six reasons why water is important to living things, like, I dunno, a kangaroo?

Answer 6

• Water has a high specific heat capacity
• Water has a high latent heat of vaporisation
• Water is incompressible
• Water is an excellent lubricant
• Water can be a biological reagent
• Water is an expert transport medium

Question 7

In the carbon cycle, what do both terrestrial and aquatic organisms exchange with the atmosphere?

Answer 7

Carbon dioxide, (C02)

Question 8

After scavengers have broken down the dead bodies of living organisms into more manageable pieces; the remains are decomposed by the saprotrophic feeding of microorganisms. Describe saprotrophic feeding.

Answer 8

The fungi and bacteria that perform the saprotrophic feeding by secreting enzymes onto the remains and absorbing the digestive products.

Question 9

What enzymes might saprotrophic feeders use to digest: a) fats, b) starch c) protein?

Answer 9

a) to digest fats, lipases
b) to digest starch, amylase
c) to digest protein, proteases

Question 10

What do living organisms require carbon-containing compounds as?

Answer 10

• a source of energy, released when carbon-containing compounds are oxidised during respiration (particularly carbohydrates and fats)
• raw materials, for the growth of cells (particularly fats and proteins)

Question 11

What four processes recycle carbon over and over and over again?

Answer 11

feeding -> respiration -> photosynthesis -> decomposition

Question 12

What happens in nitrogen fixation?

Answer 12

nitrogen and hydrogen are combined to form ammonium ions, and then nitrate.

Question 13

What does the process of nitrogen fixation depend on?

Answer 13

It depends upon enzymes that are only possessed by certain bacteria, called nitrogen-fixing bacteria.

Question 14

Describe the process of nitrification.

Answer 14

Ammonium ions produced by the decomposition of amino acids and proteins are oxidised, first to NITRITE then to NITRATE.

The process is carried out by nitrifying bacteria which live in the soil.

Nitrification only happens if oxygen is present.

Question 15

What happens if there is no oxygen present?

Answer 15

In the absence of oxygen the process of nitrification is reversed!!!

The denitrifying bacteria obtain their energy by converting nitrate into nitrogen gas.

Question 16

How does combustion of fossil fuels affect the carbon dioxide concentrations in the atmosphere?

Answer 16

Combustion of fossil fuels returns enormous amounts volumes of trapped carbon dioxide into the atmosphere.
As a result, carbon dioxide concentrations are increasing.

Question 17

How does the cutting down of forests affect the carbon dioxide concentrations in the atmosphere?

Answer 17

Cutting down trees may unbalance the carbon cycle, causing more C02 in the atmosphere as the process of photosynthesis (along with other things) plays a major role in the carbon cycle.

Question 18

Describe the carbon cycle!

Answer 18

• PHOTOSYNTHESIS uses light energy to convert carbon dioxide into organic compounds in plants.
• Animals EATDescribe the plants, and their RESPIRATION releases C02 back into the air.
• Plants and animals die and excrete. This then goes through the process of DECOMPOSITION with the help of bacteria and fungi, who in turn respire carbon dioxide back into the environment.
• Some plants, animals, bacteria and fungi are FOSSILISED, then to create fossil fuels. COMBUSTION releases carbon dioxide into the air by the burning of these fossil fuels.
• Plants consume the C02 and the cycle begins again!

Question 19

Describe the nitrogen cycle!

Answer 19

• DECOMPOSITION of plant and animal protein to AMMONIUM IONS.
• NITRIFYING BACTERIA turn the ammonium ions into NITRITE and then to NITRATE.
• So, NITROGEN FIXATION occurs by bacteria called nitrogen-fixing bacteria. Some living in the soil, but others in nodules on the roots of legumes. The only thing that can break apart the triple bond of nitrogen is nitrogenase and lightening. (Recently invented fertilisers do it too)
• Now, the nitrogen fixation has given us NITRATE IONS which can now be absorbed into the plants.
• The plants in turn make AMINO ACIDS and PROTEINS.
• Animals consume plants and digest the proteins.
• DENTRIFYING BACTERIA reverse the process of nitrification when there is no oxygen present. This turns nitrate into nitrogen gas.

Question 20

N02-

Answer 20

Nitrite

Question 21

N03-

Answer 21

Nitrate

Question 22

NH4+

Answer 22

Ammonium