B4.1.6 - Nutrient cycling

Question 1

What is nutrient cycling?

Answer 1

Plants obtain nutrients from the soil. These are passed onto the animals when eaten. When plants lose materials such as leaves, and organisms die, decomposers release the trapped nutrients. Many of the nutrients are released back into the soil, where they are absorbed by plants. Some are released back into the atmosphere

Question 2

What materials are cycled?

Answer 2

Carbon, Nitrogen and Water

Question 3

What is carbon needed for in organisms?

Answer 3

To make carbohydrates, fats, proteins, and DNA

Question 4

How much of our atmosphere does nitrogen take up?

Answer 4

Nearly 80% of the atmosphere

Question 5

What is the nitrogen cycle?

Answer 5

• Nitrogen exists as nitrates in the soil dissolved in water
• It is taken up by roots to make proteins
• When plants are eaten the nitrogen compounds pass onto the animal
• When plans and animals die, these compounds are broken down and released back into the soil as ammonia
• Animals also put nitrogen back into the soil in faeces and urea
• Some plants form mutualistic relationships with nitrogen-fixing bacteria
• These bacteria live in their roots and combine nitrogen from the air with oxygen to form nitrates which are then used by the plants

Question 6

What is the water cycle?

Answer 6

• The Sun heats the Earth’s surface and water is turned from liquid to vapour forming warm, moist air
• Loss of water vapour from plants goes directly to the atmosphere
• As moist air rises it cools. Water vapour condenses back into liquid water droplets producing clouds
• As water droplets in clouds get heavier they fall as rain, snow or hail
• Percolation (water trickling through gaps in soils and rocks) can go towards trees or the ocean

Question 7

Why do all living organisms need water?

Answer 7

Because all living organisms need to drink or absorb water to survive