Subjects
Maths
Chemistry
Biology
English Language
History
Responding to change (a2 only)
Infection and response
Homeostasis and response
Energy transfers (a2 only)
Cell biology
Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
Organisation
Substance exchange
Bioenergetics
Genetic information & variation
Inheritance, variation and evolution
Genetics & ecosystems (a2 only)
Ecology
Cells
Show all topics
Britain & the wider world: 1745 -1901
1l the quest for political stability: germany, 1871-1991
The cold war
Inter-war germany
Medieval period: 1066 -1509
2d religious conflict and the church in england, c1529-c1570
2o democracy and nazism: germany, 1918-1945
1f industrialisation and the people: britain, c1783-1885
1c the tudors: england, 1485-1603
2m wars and welfare: britain in transition, 1906-1957
World war two & the holocaust
2n revolution and dictatorship: russia, 1917-1953
2s the making of modern britain, 1951-2007
World war one
Britain: 1509 -1745
Show all topics
13
0
Zara
09/12/2025
Biology
The Nitrogen, Carbon and Water Cycle - Higher and Foundtion tier - Combained science - EDEXCEL
574
•
9 Dec 2025
•
Zara
@zara_12321
Ever wondered how nature recycles everything perfectly? The carbon, water,... Show more
Your body is made of carbon, and so is every living thing on Earth! The carbon cycle shows how this essential element moves between the air, plants, animals, and soil in an endless loop.
Photosynthesis kicks off the whole process when green plants grab CO₂ from the air to make food. When animals eat plants, they're getting those carbon compounds too. Both plants and animals release CO₂ back into the air through respiration - basically just breathing!
When living things die, decomposer bacteria and fungi break them down, releasing more CO₂. We also burn things like wood and fossil fuels (made from ancient dead plants and animals), which pumps even more CO₂ back into the atmosphere.
Key Point: The carbon cycle has multiple pathways, but they all lead back to CO₂ returning to the air - it's nature's perfect recycling system!
Think about the last time you saw water evaporate from a puddle - you were watching the water cycle in action! This process moves water around Earth using the sun's energy as the driving force.
Evaporation happens when the sun heats up water from oceans, lakes, and rivers. Plants also release water vapour through their leaves in a process called transpiration - they're basically sweating!
As water vapour rises high into the sky, it cools down and condenses into tiny droplets that form clouds. Eventually, this water falls back down as precipitation (rain, snow, or sleet), filling up our rivers, lakes, and underground water stores again.
Key Point: The water cycle is powered entirely by the sun's heat - it's like a giant solar-powered recycling machine!
Here's something mad - the air around you is 78% nitrogen, but plants can't use it directly! The nitrogen cycle solves this problem through some clever natural processes.
Lightning is so hot it breaks down nitrogen gas and creates nitrates that dissolve into soil. Special nitrogen-fixing bacteria also convert nitrogen into ammonia that plants can actually absorb through their roots to make proteins and DNA.
When animals eat plants, they get these nitrogen compounds. Animal waste and dead organisms return nitrogen to the soil, where decomposer bacteria break it down, and nitrifying bacteria convert it back into forms plants can use again.
During droughts, when there's little rainfall, we can create potable water (safe drinking water) through desalination - basically removing salt from seawater by evaporating and condensing it.
Key Point: Each cycle depends on different types of bacteria to keep the recycling process going - microorganisms are the unsung heroes of life on Earth!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
App Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Zara
@zara_12321
Ever wondered how nature recycles everything perfectly? The carbon, water, and nitrogen cycles are Earth's brilliant recycling systems that keep life going by constantly moving essential materials around our planet.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your body is made of carbon, and so is every living thing on Earth! The carbon cycle shows how this essential element moves between the air, plants, animals, and soil in an endless loop.
Photosynthesis kicks off the whole process when green plants grab CO₂ from the air to make food. When animals eat plants, they're getting those carbon compounds too. Both plants and animals release CO₂ back into the air through respiration - basically just breathing!
When living things die, decomposer bacteria and fungi break them down, releasing more CO₂. We also burn things like wood and fossil fuels (made from ancient dead plants and animals), which pumps even more CO₂ back into the atmosphere.
Key Point: The carbon cycle has multiple pathways, but they all lead back to CO₂ returning to the air - it's nature's perfect recycling system!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Think about the last time you saw water evaporate from a puddle - you were watching the water cycle in action! This process moves water around Earth using the sun's energy as the driving force.
Evaporation happens when the sun heats up water from oceans, lakes, and rivers. Plants also release water vapour through their leaves in a process called transpiration - they're basically sweating!
As water vapour rises high into the sky, it cools down and condenses into tiny droplets that form clouds. Eventually, this water falls back down as precipitation (rain, snow, or sleet), filling up our rivers, lakes, and underground water stores again.
Key Point: The water cycle is powered entirely by the sun's heat - it's like a giant solar-powered recycling machine!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Here's something mad - the air around you is 78% nitrogen, but plants can't use it directly! The nitrogen cycle solves this problem through some clever natural processes.
Lightning is so hot it breaks down nitrogen gas and creates nitrates that dissolve into soil. Special nitrogen-fixing bacteria also convert nitrogen into ammonia that plants can actually absorb through their roots to make proteins and DNA.
When animals eat plants, they get these nitrogen compounds. Animal waste and dead organisms return nitrogen to the soil, where decomposer bacteria break it down, and nitrifying bacteria convert it back into forms plants can use again.
During droughts, when there's little rainfall, we can create potable water (safe drinking water) through desalination - basically removing salt from seawater by evaporating and condensing it.
Key Point: Each cycle depends on different types of bacteria to keep the recycling process going - microorganisms are the unsung heroes of life on Earth!
Our AI Companion is a student-focused AI tool that offers more than just answers. Built on millions of Knowunity resources, it provides relevant information, personalised study plans, quizzes, and content directly in the chat, adapting to your individual learning journey.
You can download the app from Google Play Store and Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
13
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the key differences between exothermic and endothermic reactions, including definitions, examples like combustion and hand warmers, and their effects on surrounding temperatures. This summary provides a clear understanding of energy transfer in chemical processes.
BiologyExplore key concepts in ecology, including biodiversity, the carbon cycle, and the impact of human activities on ecosystems. This summary covers essential topics such as decay processes, food chains, and the role of biotechnology in food security. Ideal for GCSE Biology AQA Triple students preparing for exams.
BiologyExplore the essential roles of glucose in respiration, photosynthesis, and metabolism. Understand how environmental factors like light intensity, temperature, and carbon dioxide concentration affect photosynthesis rates. This summary covers aerobic and anaerobic respiration, including equations and practical investigations for GCSE AQA biology.
BiologyHigher tier combined science flashcards about topics on Biology paper 1
BiologyExplore the Nitrogen Cycle's key processes, including nitrogen fixation, the role of natural and artificial fertilizers, and methods for restoring soil fertility. This summary covers essential concepts for GCSE Biology, focusing on nutrient cycles, plant nutrition, and the impact of fertilizers on agriculture and the environment.
Biologycell biology flash cards for gsce!
BiologyApp Store
Google Play
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
The app is very easy to use and well designed. I have found everything I was looking for so far and have been able to learn a lot from the presentations! I will definitely use the app for a class assignment! And of course it also helps a lot as an inspiration.
Stefan S
iOS user
This app is really great. There are so many study notes and help [...]. My problem subject is French, for example, and the app has so many options for help. Thanks to this app, I have improved my French. I would recommend it to anyone.
Samantha Klich
Android user
Wow, I am really amazed. I just tried the app because I've seen it advertised many times and was absolutely stunned. This app is THE HELP you want for school and above all, it offers so many things, such as workouts and fact sheets, which have been VERY helpful to me personally.
Anna
iOS user
Best app on earth! no words because it’s too good
Thomas R
iOS user
Just amazing. Let's me revise 10x better, this app is a quick 10/10. I highly recommend it to anyone. I can watch and search for notes. I can save them in the subject folder. I can revise it any time when I come back. If you haven't tried this app, you're really missing out.
Basil
Android user
This app has made me feel so much more confident in my exam prep, not only through boosting my own self confidence through the features that allow you to connect with others and feel less alone, but also through the way the app itself is centred around making you feel better. It is easy to navigate, fun to use, and helpful to anyone struggling in absolutely any way.
David K
iOS user
The app's just great! All I have to do is enter the topic in the search bar and I get the response real fast. I don't have to watch 10 YouTube videos to understand something, so I'm saving my time. Highly recommended!
Sudenaz Ocak
Android user
In school I was really bad at maths but thanks to the app, I am doing better now. I am so grateful that you made the app.
Greenlight Bonnie
Android user
very reliable app to help and grow your ideas of Maths, English and other related topics in your works. please use this app if your struggling in areas, this app is key for that. wish I'd of done a review before. and it's also free so don't worry about that.
Rohan U
Android user
I know a lot of apps use fake accounts to boost their reviews but this app deserves it all. Originally I was getting 4 in my English exams and this time I got a grade 7. I didn’t even know about this app three days until the exam and it has helped A LOT. Please actually trust me and use it as I’m sure you too will see developments.
Xander S
iOS user
THE QUIZES AND FLASHCARDS ARE SO USEFUL AND I LOVE THE SCHOOLGPT. IT ALSO IS LITREALLY LIKE CHATGPT BUT SMARTER!! HELPED ME WITH MY MASCARA PROBLEMS TOO!! AS WELL AS MY REAL SUBJECTS ! DUHHH 😍😁😲🤑💗✨🎀😮
Elisha
iOS user
This apps acc the goat. I find revision so boring but this app makes it so easy to organize it all and then you can ask the freeeee ai to test yourself so good and you can easily upload your own stuff. highly recommend as someone taking mocks now
Paul T
iOS user
Biology
Sociology