Biology
Chemistry
AP Chemistry
English
AP English Literature
8
0
Drizzle Hinata
11/30/2025
AP Environmental Science
BIOGEOCHEMICAL CYCLES
128
•
Nov 30, 2025
•
Biogeochemical cycles are the essential pathways that move chemical elements... Show more
Ever wonder how nutrients get recycled in nature? Biogeochemical cycles move essential elements through the environment and living organisms in continuous loops. These cycles have two main components: reservoir pools and cycling pools (smaller, active portions that exchange rapidly between organisms and their environment).
There are two basic groups of biogeochemical cycles. Gaseous cycles involve elements that circulate through the atmosphere or hydrosphere (water systems). Sedimentary cycles involve elements primarily found in Earth's crust. Major biogeochemical cycles include phosphorus, sulfur, carbon, and the water cycle.
The nitrogen cycle is particularly important since nitrogen is essential for building proteins. Plants cannot use atmospheric nitrogen directly - it must be converted to forms like nitrates, which plants can absorb. Animals then get nitrogen by eating plants or other animals.
💡 Think of biogeochemical cycles as nature's recycling system - nothing is wasted, and elements keep moving from one place to another in predictable patterns.
Nitrogen makes up 78% of our atmosphere, but most living things can't use it directly! Nitrogen fixation converts atmospheric nitrogen into usable forms through several processes. Natural processes like cosmic radiation, meteorite trails, and lightning account for some fixation, but biological fixation is responsible for 90% of it.
Biological nitrogen fixation is performed by special bacteria and cyanobacteria (like Anabaena and Nostoc). These organisms use an enzyme called nitrogenase to break down N₂ gas. Some plants, like Azolla, form partnerships with these bacteria to get nitrogen directly. When organisms die, decomposers break down their proteins through ammonification, releasing ammonia.
The nitrogen cycle continues through nitrification, where bacteria convert ammonia to nitrite (Nitrosomonas bacteria) and then to nitrate (Nitrobacter bacteria). Plants easily absorb nitrates from the soil. Finally, denitrification by bacteria like Pseudomonas converts fixed nitrogen back to N₂ gas, completing the cycle.
🔍 The nitrogen cycle demonstrates an amazing partnership between different organisms: bacteria fix nitrogen, plants use it to grow, animals eat the plants, and decomposers recycle it when organisms die.
The phosphorus cycle is unique because it doesn't have a significant atmospheric component. Phosphorus moves through ecosystems in three main states: particulate organic phosphorus, dissolved organic phosphates, and inorganic phosphates. In aquatic systems, phosphates are quickly taken up by phytoplankton, then eaten by zooplankton, which excrete phosphorus daily.
The sulfur cycle combines both sedimentary and gaseous phases. Sulfur enters the atmosphere through fossil fuel burning, volcanic eruptions, ocean surface exchanges, and decomposition gases. In the atmosphere, hydrogen sulfide (H₂S) converts to sulfur dioxide (SO₂). Atmospheric sulfur returns to Earth's surface in rainwater as weak sulfuric acid (H₂SO₄).
Different bacteria play crucial roles in the sulfur cycle. Sulfur bacteria can reduce hydrogen sulfide to elemental sulfur and oxidize it to sulfuric acid. Green and purple bacteria use H₂S in the presence of light for photosynthesis, with purple bacteria commonly found in salt marshes and estuaries.
🌱 The next time you use fertilizer, remember that you're participating in the phosphorus cycle! Fertilizers often contain phosphates that help plants grow, just like in natural ecosystems.
The carbon cycle moves this essential element between the atmosphere, oceans, soil, and living organisms. Carbon dioxide (CO₂) from the atmosphere is absorbed by plants and phytoplankton, which convert it to organic carbon through photosynthesis. When animals eat plants, this carbon transfers through the food chain.
When organisms die, decomposing bacteria break down organic matter, releasing carbon back to the atmosphere as CO₂. In marine environments, carbon can form carbonate compounds that may eventually become sediments on the ocean floor. Over millions of years, these sediments can form limestone or fossil fuels.
The carbon cycle maintains the balance of carbon in our atmosphere, which regulates Earth's temperature. Human activities like burning fossil fuels and deforestation have increased atmospheric carbon dioxide, disrupting this natural cycle.
🔄 Every breath you take connects you to the carbon cycle! When you exhale CO₂, you're returning carbon to the atmosphere that will eventually be used by plants in photosynthesis.
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the 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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
Biogeochemical cycles are the essential pathways that move chemical elements between the environment and living organisms. These cycles ensure that nutrients necessary for life continuously circulate throughout the Earth's systems, making them fundamental to understanding how ecosystems function.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Ever wonder how nutrients get recycled in nature? Biogeochemical cycles move essential elements through the environment and living organisms in continuous loops. These cycles have two main components: reservoir pools and cycling pools (smaller, active portions that exchange rapidly between organisms and their environment).
There are two basic groups of biogeochemical cycles. Gaseous cycles involve elements that circulate through the atmosphere or hydrosphere (water systems). Sedimentary cycles involve elements primarily found in Earth's crust. Major biogeochemical cycles include phosphorus, sulfur, carbon, and the water cycle.
The nitrogen cycle is particularly important since nitrogen is essential for building proteins. Plants cannot use atmospheric nitrogen directly - it must be converted to forms like nitrates, which plants can absorb. Animals then get nitrogen by eating plants or other animals.
💡 Think of biogeochemical cycles as nature's recycling system - nothing is wasted, and elements keep moving from one place to another in predictable patterns.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Nitrogen makes up 78% of our atmosphere, but most living things can't use it directly! Nitrogen fixation converts atmospheric nitrogen into usable forms through several processes. Natural processes like cosmic radiation, meteorite trails, and lightning account for some fixation, but biological fixation is responsible for 90% of it.
Biological nitrogen fixation is performed by special bacteria and cyanobacteria (like Anabaena and Nostoc). These organisms use an enzyme called nitrogenase to break down N₂ gas. Some plants, like Azolla, form partnerships with these bacteria to get nitrogen directly. When organisms die, decomposers break down their proteins through ammonification, releasing ammonia.
The nitrogen cycle continues through nitrification, where bacteria convert ammonia to nitrite (Nitrosomonas bacteria) and then to nitrate (Nitrobacter bacteria). Plants easily absorb nitrates from the soil. Finally, denitrification by bacteria like Pseudomonas converts fixed nitrogen back to N₂ gas, completing the cycle.
🔍 The nitrogen cycle demonstrates an amazing partnership between different organisms: bacteria fix nitrogen, plants use it to grow, animals eat the plants, and decomposers recycle it when organisms die.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The phosphorus cycle is unique because it doesn't have a significant atmospheric component. Phosphorus moves through ecosystems in three main states: particulate organic phosphorus, dissolved organic phosphates, and inorganic phosphates. In aquatic systems, phosphates are quickly taken up by phytoplankton, then eaten by zooplankton, which excrete phosphorus daily.
The sulfur cycle combines both sedimentary and gaseous phases. Sulfur enters the atmosphere through fossil fuel burning, volcanic eruptions, ocean surface exchanges, and decomposition gases. In the atmosphere, hydrogen sulfide (H₂S) converts to sulfur dioxide (SO₂). Atmospheric sulfur returns to Earth's surface in rainwater as weak sulfuric acid (H₂SO₄).
Different bacteria play crucial roles in the sulfur cycle. Sulfur bacteria can reduce hydrogen sulfide to elemental sulfur and oxidize it to sulfuric acid. Green and purple bacteria use H₂S in the presence of light for photosynthesis, with purple bacteria commonly found in salt marshes and estuaries.
🌱 The next time you use fertilizer, remember that you're participating in the phosphorus cycle! Fertilizers often contain phosphates that help plants grow, just like in natural ecosystems.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The carbon cycle moves this essential element between the atmosphere, oceans, soil, and living organisms. Carbon dioxide (CO₂) from the atmosphere is absorbed by plants and phytoplankton, which convert it to organic carbon through photosynthesis. When animals eat plants, this carbon transfers through the food chain.
When organisms die, decomposing bacteria break down organic matter, releasing carbon back to the atmosphere as CO₂. In marine environments, carbon can form carbonate compounds that may eventually become sediments on the ocean floor. Over millions of years, these sediments can form limestone or fossil fuels.
The carbon cycle maintains the balance of carbon in our atmosphere, which regulates Earth's temperature. Human activities like burning fossil fuels and deforestation have increased atmospheric carbon dioxide, disrupting this natural cycle.
🔄 Every breath you take connects you to the carbon cycle! When you exhale CO₂, you're returning carbon to the atmosphere that will eventually be used by plants in photosynthesis.
Our AI companion is specifically built for the needs of students. Based on the millions of content pieces we have on the platform we can provide truly meaningful and relevant answers to students. But its not only about answers, the companion is even more about guiding students through their daily learning challenges, with personalised study plans, quizzes or content pieces in the chat and 100% personalisation based on the students skills and developments.
You can download the app in the Google Play Store and in the Apple App Store.
That's right! Enjoy free access to study content, connect with fellow students, and get instant help – all at your fingertips.
8
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
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
I think it’s very much worth it and you’ll end up using it a lot once you get the hang of it and even after looking at others notes you can still ask your Artificial intelligence buddy the question and ask to simplify it if you still don’t get it!!! In the end I think it’s worth it 😊👍 ⚠️Also DID I MENTION ITS FREEE YOU DON’T HAVE TO PAY FOR ANYTHING AND STILL GET YOUR GRADES IN PERFECTLY❗️❗️⚠️
Thomas R
iOS user
Knowunity is the BEST app I’ve used in a minute. This is not an ai review or anything this is genuinely coming from a 7th grade student (I know 2011 im young) but dude this app is a 10/10 i have maintained a 3.8 gpa and have plenty of time for gaming. I love it and my mom is just happy I got good grades
Brad T
Android user
Not only did it help me find the answer but it also showed me alternative ways to solve it. I was horrible in math and science but now I have an a in both subjects. Thanks for the help🤍🤍
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
I found this app a couple years ago and it has only gotten better since then. I really love it because it can help with written questions and photo questions. Also, it can find study guides that other people have made as well as flashcard sets and practice tests. The free version is also amazing for students who might not be able to afford it. Would 100% recommend
Aubrey
iOS user
Best app if you're in Highschool or Junior high. I have been using this app for 2 school years and it's the best, it's good if you don't have anyone to help you with school work.😋🩷🎀
Marco B
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 app is phenomenal down to the correct info and the various topics you can study! I greatly recommend it for people who struggle with procrastination and those who need homework help. It has been perfectly accurate for world 1 history as far as I’ve seen! Geometry too!
Paul T
iOS user
