Unit 1 Nitrogen Cycle

Why do plants need nitrogen?

To make proteins for growth

Where do animals get their proteins from?

By feeding on plants, digesting their proteins and then building them back up into animal protein

What form do plants get their nitrogen?

As nitrates from soil - cannot use nitrogen directly from air

How exactly do plants obtain nitrates from the soil?

Absorb nitrates by process of active uptake using root hair cells

What is active uptake?

Energy requiring absorption of ions against the concentration gradient i.e from a lower to a higher concentration

How are root cells adapted for active uptake?

Long extentions named root hairs which provide a large SA

Why does this process work best in well oxygenated soils?

Active transport requires energy from resp and resp requires oxygen

What is nitrification?

Carried out by nitrifying bacteria - ammonium compounds/ammonia are converted to nitrates

Where do ammonium ions/ammonia come from?

They come from the breakdown of animal and plant proteins during decomposition of dead material and waste products

What is denitrification?

Carried out by denitrifying bacteria - nitrates in the soil are changed back into nitrogen gas in the air

Name for special group of plants that can convert nitrogen gas into the air directly into usable nitrates

Legumes e.g peas, beans, clover

How are legumes able to convert nitrogen gas into usable nitrates?

They have nitrogen fixing bacteria in swellings on their roots called root nodules

Why do farmers often deliberately plant a field with legumes?

They raise the nitrate content of the soil, making it better for growing a crop

Which process in the nitrogen cycle do farmers try and minimise and why?

Detrification because it lowers the nitrate content of the soil

What sort of conditions do the denitriftinf bacteria involved in denitrication thrive in?

Low O2 (anaerobic), typical of waterlogged, poorly drained soils

Name 3 key minerals in the soil that plants need and say why they’re needed

• Magnesium - make chlorophyll

• Nitrates - to form amino acids and proteins for growth

• Calcium - make cell walls

What are the 2 types of fertiliser?

Natural and artificial

Diff between natural and artificial fertiliser

• Comes from farmyard manure, compost and slurry

• Man-made containing known quantities of minerals

Suggest an advantage of natural fertiliser.

Decomposed naturally and doesn’t cause pollution

Suggest an advantage of artificial fertiliser

Contains known amounts of minerals being soluble, they are rapidly absorbed by plants

Suggest a disadvantage of natural fertiliser

Takes a while for decomposers to decompose it

Suggest a disadvantage of artificial fertiliser

Heavy rain can cause fertiliser runoff from the soil and leaching into rivers, causing pollution

How can human activity effect biodiversity positively?

• Reforestation i.e re-planting trees

• Develop sustainable woodlands to meet commercial needs

• International Treaties

Name two international treaties

Kyoto Protocol and Paris Agreement

What is the name of the water pollution due to runoff of fertiliser?

Eutrophication