Chemical cycle

It is the main ingredient in all organic compounds such as proteins,

carbohydrates, fats and nucleic acids

• N

• O

• C

• H

The carbon cycle begins with the process of:

• a) Respiration

• b) Decomposition

• c) Photosynthesis

• d) Weathering

When herbivores consume plants, carbon moves to:

• The atmosphere directly

• Limestone rocks. , ,

• Their body cells

Fixed carbon in limestone returns to the atmosphere through:

• Decomposition

• b) Fossil fuel combustion

• Evaporation

Nitrogen fixation is carried out by:

• ia) Certain bacteria

• b) Plants

• c) Organic decomposition

• d) Herbivores

In the nitrogen cycle, ammonia is converted to nitrates by:

• a) plants

• b) Fungi

• c) Nitrifying bacteria

• d) Animals

Phosphorus plays an important role in energy storage and transfer in cells

through

d) DNA

• a) Proteins

• b) Carbohydrates

• c) ATP

Nitrogen-fixing bacteria convert nitrogen into:

• a) Nitrite

• b) Ammonia

• c) Nitrate

• d) Nitrous oxide

Rain helps to:

• a) Increase carbon levels in the atmosphere

• b) Transfer nutrients to the soil

• c) Reduce carbon dioxide

• d) Increase weathering

The nitrogen cycle is negatively affected by:

• a) Plant cultivation

• b) Low evaporation

• c) Increased pollution from fertilizers

• d) Lack of rainfall