Recycling In Ecosystems

Question 1

What is the carbon cycle?

Answer 1

How carbon moves from living organisms and the nonliving environment

Question 2

What processes does the carbon cycle include?

Answer 2

• photosynthesis, respiration, and decomposition

- also chemical and physical processes such as combustion and weathering

Question 3

Explain what the different stages/steps of the carbon cycle are?

Answer 3

1. Carbon is absorbed by plants when they carry out photosynthesis – it becomes carbon compounds in plant tissues
2. Carbon is passed on to primary consumers when they eat the plants. It’s passed onto secondary and tertiary consumers when they eat other consumers
3. All living organisms die and the carbon compounds in the dead organisms are digested by microorganisms called decomposes E.G bacteria and fungi. Feeding on dead organic matter is called saprobiontic nutrition
4. Carbon is returned to the air as all living organisms carry out respiration which produces CO2
5. If dead organic matter end up in places where there aren’t any decomposers that carbon compounds can be turned into fossil fuels over millions of years
6. The carbon in fossil fuels e.g oil and coal is released when they are burnt – this is called combustion
7. Rocks such as limestone and chalk are mainly composed of calcium carbonate. This comes from marine organisms like crabs and coral that utilise this compound in the development e.g. shells
8. One way carbon can be returned to the atmosphere from these rocks is by them being drawn down deep into the earths crust by the movement of tectonic plates. They then undergo chemical changes and release carbon dioxide which is returned to the atmosphere by volcanoes

Question 4

Why do plants and animals need nitrogen, and what must happen to it first for it to be useable?

Answer 4

• They need nitrogen to make proteins and nucleic acids

- they can’t use nitrogen in the atmosphere as they need bacteria to convert it into nitrogen compounds first

Question 5

What is the nitrogen cycle?

Answer 5

It shows how nitrogen is converted into a usable form and then passed on between different living organisms and nonliving environment

Question 6

What are the four processes that involve bacteria included in the nitrogen cycle?

Answer 6

• nitrogen fixation
• ammonification
• nitrification
• dentrification

Question 7

Explain the process of nitrogen fixation

Answer 7

-when nitrogen gas in the atmosphere is turned into ammonia by bacteria, such as Rhizobium , so the ammonia can be used by plants
-Rhizobium are found inside root nodules of leguminous plants e.g peas
-they form a mutualistic relationship with plants, as they provide the plants with the nitrogen compounds, and the plants provide carbohydrates

Question 8

Explain the process of ammonification

Answer 8

• when nitrogen compounds from dead organisms are turned into ammonia by decomposers, which goes onto form ammonium ions
• animal waste (urine and faeces) also contain nitrogen compounds, which are also turned into ammonia by decomposers and go on to form ammonium ions

Question 9

Explain the process of nitrification

Answer 9

• when ammonium ions in the soil are changed into nitrogen compounds that can be used by plants, called nitrates
• it’s a 2 step process:
• first nitrifying bacteria called nitrosomonas change ammonium ions into nitrites
• then over nitrifying bacteria called nitrobacter change nitrites into nitrates

Question 10

Explain the process of dentrification

Answer 10

• when nitrites in the soil are converted into nitrogen gas by denitrifying bacteria
• they use nitrates in the soil to carry out respiration and produce nitrogen gas
• this happens under anaerobic conditions where there’s no oxygen e.g in waterlogged soils

Question 11

What are 2 other ways that nitrogen can get into an ecosystem?

Answer 11

1. Lightning= fixes atmospheric nitrogen

2. Artificial fertilisers= produced from atmospheric nitrogen