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
3
0
Chen Ye Wu
10/12/2025
Biology
what is life - biology
30
•
10 Dec 2025
•
Chen Ye Wu
@chenyewu_zqgp
Ever wondered what separates living things from non-living objects? Biology... Show more
You might think it's obvious what's alive and what's not, but scientists need clear rules to decide. Living organisms must have all seven key properties of life - miss just one and you're not considered alive!
The first property is organisation. All living things are incredibly well-organised, made up of specialised parts that work together perfectly. Every organism contains at least one cell, which scientists call the fundamental unit of life.
Even if you're just a single cell, you're amazingly complex inside! In multicellular organisms like humans, similar cells group together to form tissues (like muscle or nervous tissue). These tissues then combine to create organs (like your heart or lungs), which work together in organ systems.
Quick Tip: Think of organisation like a school - individual students (cells) form classes (tissues), which make up year groups (organs), all working together as one school (organism)!
The second crucial property is metabolism - all the chemical reactions happening inside an organism. These reactions let you move, grow, and stay alive by using energy and nutrients.
Metabolism splits into two types: anabolism (building complex molecules from simple ones) and catabolism (breaking down complex molecules). Think of anabolism as construction work that uses energy, whilst catabolism is like demolition that releases stored energy.
Homeostasis means keeping your internal environment stable, even when the outside world changes. Your body temperature stays around 37°C whether it's freezing or boiling outside - that's homeostasis in action!
Growth happens when individual cells get bigger or when organisms gain more cells through cell division. You started as just one cell and now have tens of trillions - pretty impressive growth!
Living things can reproduce to create new organisms. This happens through asexual reproduction (one parent) or sexual reproduction (two parents). Even simple bacteria can reproduce by just splitting in two.
Remember: All living things respond to their environment - you pull your hand from fire, plants turn toward sunlight, and even tiny organisms move toward food!
Finally, populations of living things undergo evolution. Through natural selection, helpful traits become more common over generations, making populations better suited to their environments through adaptation.
Scientists don't always agree on the exact list of life's properties. Some include movement as essential, others focus on DNA as genetic material, whilst some emphasise that life is carbon-based.
The most puzzling case? Viruses. These tiny structures made of protein and genetic material can reproduce, but only inside host cells. They don't have their own cellular structure, can't reproduce independently, and don't carry out their own metabolism.
So are viruses alive or not? Scientists still debate this question! They have some properties of life but lack others, making them a perfect example of why defining life remains one of biology's most interesting challenges.
Think About It: If we discover life on other planets, it might be so different from Earth life that we'll need to completely rethink our definition of what it means to be alive!
This ongoing debate shows that biology is a living science - our understanding keeps evolving as we learn more about the incredible diversity of life around us.
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.
Quotes from every main character
English LiteratureApp 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
Chen Ye Wu
@chenyewu_zqgp
Ever wondered what separates living things from non-living objects? Biology is the study of life, but defining what actually counts as "alive" is trickier than you might think. Scientists use specific properties to identify living organisms, though even they sometimes... Show more
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You might think it's obvious what's alive and what's not, but scientists need clear rules to decide. Living organisms must have all seven key properties of life - miss just one and you're not considered alive!
The first property is organisation. All living things are incredibly well-organised, made up of specialised parts that work together perfectly. Every organism contains at least one cell, which scientists call the fundamental unit of life.
Even if you're just a single cell, you're amazingly complex inside! In multicellular organisms like humans, similar cells group together to form tissues (like muscle or nervous tissue). These tissues then combine to create organs (like your heart or lungs), which work together in organ systems.
Quick Tip: Think of organisation like a school - individual students (cells) form classes (tissues), which make up year groups (organs), all working together as one school (organism)!
The second crucial property is metabolism - all the chemical reactions happening inside an organism. These reactions let you move, grow, and stay alive by using energy and nutrients.
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Metabolism splits into two types: anabolism (building complex molecules from simple ones) and catabolism (breaking down complex molecules). Think of anabolism as construction work that uses energy, whilst catabolism is like demolition that releases stored energy.
Homeostasis means keeping your internal environment stable, even when the outside world changes. Your body temperature stays around 37°C whether it's freezing or boiling outside - that's homeostasis in action!
Growth happens when individual cells get bigger or when organisms gain more cells through cell division. You started as just one cell and now have tens of trillions - pretty impressive growth!
Living things can reproduce to create new organisms. This happens through asexual reproduction (one parent) or sexual reproduction (two parents). Even simple bacteria can reproduce by just splitting in two.
Remember: All living things respond to their environment - you pull your hand from fire, plants turn toward sunlight, and even tiny organisms move toward food!
Finally, populations of living things undergo evolution. Through natural selection, helpful traits become more common over generations, making populations better suited to their environments through adaptation.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Scientists don't always agree on the exact list of life's properties. Some include movement as essential, others focus on DNA as genetic material, whilst some emphasise that life is carbon-based.
The most puzzling case? Viruses. These tiny structures made of protein and genetic material can reproduce, but only inside host cells. They don't have their own cellular structure, can't reproduce independently, and don't carry out their own metabolism.
So are viruses alive or not? Scientists still debate this question! They have some properties of life but lack others, making them a perfect example of why defining life remains one of biology's most interesting challenges.
Think About It: If we discover life on other planets, it might be so different from Earth life that we'll need to completely rethink our definition of what it means to be alive!
This ongoing debate shows that biology is a living science - our understanding keeps evolving as we learn more about the incredible diversity of life around us.
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.
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Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the essential processes of aerobic and anaerobic respiration, including key equations, energy release, and the role of lactic acid. This summary covers cellular respiration, fermentation, and their significance in energy production for living organisms. Ideal for students studying cellular bioenergetics.
BiologyExplore the key concepts of anaerobic respiration, including the process of lactic acid fermentation, energy release, and the implications of oxygen debt. This summary covers essential topics such as glycolysis, the differences between aerobic and anaerobic processes, and the role of lactic acid in muscle fatigue. Ideal for GCSE Biology students.
BiologyExplore the key differences between aerobic and anaerobic respiration in this concise summary. Understand the processes of cellular respiration, including the role of glucose, oxygen, and the byproducts of each type. Learn about metabolism, energy transfer, and the significance of fermentation in yeast and plants. Ideal for biology students studying bioenergetics and cellular metabolism.
BiologyExplore the key differences between aerobic and anaerobic respiration, including energy transfer, ATP production, and the role of enzymes. This summary covers the processes involved, equations, and implications for organisms during strenuous exercise. Ideal for students studying cellular energetics and bioenergetics.
BiologyExplore the complete process of respiration for AQA A-Level Biology, covering glycolysis, the Krebs cycle, and both aerobic and anaerobic pathways. Understand ATP production, fermentation processes, and oxidative phosphorylation with clear diagrams and explanations.
BiologyExplore the processes of aerobic and anaerobic respiration, including energy transfer, metabolic reactions, and the role of enzymes. This summary covers key concepts such as oxygen debt, lactic acid buildup, and fermentation in yeast, providing essential insights for understanding cellular energetics and metabolism. Ideal for biology revision.
BiologyQuotes from every main character
English LiteratureApp 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
Sociology