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
Biology
4 Dec 2025
148
20 pages
Darcey Greer @arceyreer_st2q1zoeyq
Biology is all about understanding living things and how they work! From tiny cells to complex organisms, you'll... Show more
Every living thing shares seven key characteristics that make them alive. Think of these as the essential "life checklist" - if something ticks all these boxes, it's definitely living!
Movement means changing position or moving body parts. Respiration is how organisms release energy using oxygen. Sensitivity is detecting changes in the environment around you. Growth is a permanent increase in size.
Reproduction creates new life, whilst excretion removes waste products like carbon dioxide. Finally, nutrition is obtaining the food needed for health and energy.
Quick Tip Remember MRS GREN to memorise all seven life processes!
Different cells have evolved special features to do specific jobs really well. Hair root cells absorb water with their long projections that increase surface area. Palisade cells contain loads of chloroplasts to capture sunlight for photosynthesis.
Ciliated epithelial cells have tiny hairs that sweep mucus away from your lungs. Sperm cells have tails to help them swim towards egg cells during reproduction.
Every cell has key parts the cytoplasm , nucleus (contains genetic information), and cell membrane (controls what enters and leaves).
Remember Each cell's shape and features perfectly match its function!
Plant cells have three extra parts that animal cells don't have. The cell wall gives structure and strength, whilst the vacuole stores water and maintains shape through pressure.
Chloroplasts contain chlorophyll, which absorbs light energy to combine carbon dioxide and water into sugar during photosynthesis. This is how plants make their own food!
Plant structure is beautifully organised roots absorb water and nutrients from soil, leaves capture sunlight for photosynthesis, and the stem provides support and transport.
Key Difference Only plant cells have cell walls, vacuoles, and chloroplasts - that's what makes them green and self-sufficient!
Microscopes help us see tiny cells clearly. The eyepiece lens (×10) works with objective lenses (×4, ×10, ×40) to magnify specimens. Simply multiply the numbers together for total magnification!
Variation explains why we're all different. Genes made of DNA cause discontinuous variation like eye colour or tongue rolling - you either can or can't do it.
Environmental factors cause continuous variation like height, where there's a gradual range across the population. Both types of variation make life interesting and diverse!
Top Tip Always start with the lowest magnification on a microscope, then zoom in gradually!
Your body constantly burns glucose with oxygen to release energy through respiration. The equation is Glucose + Oxygen → Carbon dioxide + Water + Energy.
This energy powers everything movement, growth, cell repair, and your nervous system. Your respiratory system includes the trachea, bronchi, and millions of tiny alveoli in your lungs.
Gas exchange happens in the alveoli, where oxygen enters your blood and carbon dioxide leaves. It's like a constant swap shop for gases!
Amazing Fact You have about 300 million alveoli providing a surface area the size of a tennis court!
Breathing involves two muscle groups working together. Intercostal muscles between your ribs and the diaphragm below your lungs create pressure changes.
When you inhale, ribs lift up, the diaphragm flattens, volume increases, pressure decreases, and air rushes in. Exhaling reverses this process completely.
Alveoli are perfectly designed for gas exchange they're numerous, thin-walled, moist, and have excellent blood supply. Tissues are groups of similar cells, whilst organs combine different tissue types.
Remember Breathing is automatic, but understanding the mechanics helps explain how efficiently your body works!
Smoking damages your body in multiple ways. Nicotine increases blood pressure and heart rate whilst being highly addictive. Tar narrows lung tubes and damages protective cilia. Carbon monoxide reduces oxygen-carrying capacity in blood.
Food tests help identify nutrients. Iodine turns blue-black with starch, Benedict's solution changes from blue to brick red with sugar, and Biuret reagent turns purple with protein.
Different graphs show data in various ways histograms for height, bar charts for categories like tongue rolling, and scatter graphs for experiments.
Health Warning Passive smoking affects non-smokers too - there's no safe level of smoke exposure!
The ethanol test for fats involves adding ethanol then water - a cloudy white colour indicates fat presence. These tests are essential for understanding nutrition and diet.
Creating an onion slide teaches basic microscopy skills. You'll peel the epidermis, add water and iodine, then carefully place a cover slip before observing under the microscope.
These practical skills help you see cell structures clearly and understand how different nutrients affect our bodies.
Lab Tip Always lower cover slips slowly using a mounted needle to avoid air bubbles!
Your nucleus contains 46 chromosomes arranged in 23 pairs. These thread-like structures are made of DNA, which contains genes that code for your characteristics.
Genes are like instruction manuals written in DNA that determine everything from eye colour to height. They're passed from parents to children during reproduction.
Continuous variation shows gradual differences (like height), whilst discontinuous variation creates clear categories (like blood type). Both types make every person unique!
Mind-Blowing If you stretched out all the DNA in one cell, it would be about 2 metres long!
Testing energy content in food involves burning samples under water and measuring temperature change. Different foods release different amounts of energy when burned.
A balanced diet means getting the right amounts of all seven food groups. Your energy requirements depend on age, job, activity level, and health status.
Understanding nutrition helps you make better food choices and explains why different people need different amounts of energy throughout their lives.
Personal Connection Athletes need more energy than desk workers - your lifestyle directly affects your nutritional needs!
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.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
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
Darcey Greer
@arceyreer_st2q1zoeyq
Biology is all about understanding living things and how they work! From tiny cells to complex organisms, you'll discover the amazing processes that keep everything alive and functioning.
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Every living thing shares seven key characteristics that make them alive. Think of these as the essential "life checklist" - if something ticks all these boxes, it's definitely living!
Movement means changing position or moving body parts. Respiration is how organisms release energy using oxygen. Sensitivity is detecting changes in the environment around you. Growth is a permanent increase in size.
Reproduction creates new life, whilst excretion removes waste products like carbon dioxide. Finally, nutrition is obtaining the food needed for health and energy.
Quick Tip: Remember MRS GREN to memorise all seven life processes!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Different cells have evolved special features to do specific jobs really well. Hair root cells absorb water with their long projections that increase surface area. Palisade cells contain loads of chloroplasts to capture sunlight for photosynthesis.
Ciliated epithelial cells have tiny hairs that sweep mucus away from your lungs. Sperm cells have tails to help them swim towards egg cells during reproduction.
Every cell has key parts: the cytoplasm , nucleus (contains genetic information), and cell membrane (controls what enters and leaves).
Remember: Each cell's shape and features perfectly match its function!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Plant cells have three extra parts that animal cells don't have. The cell wall gives structure and strength, whilst the vacuole stores water and maintains shape through pressure.
Chloroplasts contain chlorophyll, which absorbs light energy to combine carbon dioxide and water into sugar during photosynthesis. This is how plants make their own food!
Plant structure is beautifully organised: roots absorb water and nutrients from soil, leaves capture sunlight for photosynthesis, and the stem provides support and transport.
Key Difference: Only plant cells have cell walls, vacuoles, and chloroplasts - that's what makes them green and self-sufficient!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Microscopes help us see tiny cells clearly. The eyepiece lens (×10) works with objective lenses (×4, ×10, ×40) to magnify specimens. Simply multiply the numbers together for total magnification!
Variation explains why we're all different. Genes made of DNA cause discontinuous variation like eye colour or tongue rolling - you either can or can't do it.
Environmental factors cause continuous variation like height, where there's a gradual range across the population. Both types of variation make life interesting and diverse!
Top Tip: Always start with the lowest magnification on a microscope, then zoom in gradually!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your body constantly burns glucose with oxygen to release energy through respiration. The equation is: Glucose + Oxygen → Carbon dioxide + Water + Energy.
This energy powers everything: movement, growth, cell repair, and your nervous system. Your respiratory system includes the trachea, bronchi, and millions of tiny alveoli in your lungs.
Gas exchange happens in the alveoli, where oxygen enters your blood and carbon dioxide leaves. It's like a constant swap shop for gases!
Amazing Fact: You have about 300 million alveoli providing a surface area the size of a tennis court!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Breathing involves two muscle groups working together. Intercostal muscles between your ribs and the diaphragm below your lungs create pressure changes.
When you inhale, ribs lift up, the diaphragm flattens, volume increases, pressure decreases, and air rushes in. Exhaling reverses this process completely.
Alveoli are perfectly designed for gas exchange: they're numerous, thin-walled, moist, and have excellent blood supply. Tissues are groups of similar cells, whilst organs combine different tissue types.
Remember: Breathing is automatic, but understanding the mechanics helps explain how efficiently your body works!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Smoking damages your body in multiple ways. Nicotine increases blood pressure and heart rate whilst being highly addictive. Tar narrows lung tubes and damages protective cilia. Carbon monoxide reduces oxygen-carrying capacity in blood.
Food tests help identify nutrients. Iodine turns blue-black with starch, Benedict's solution changes from blue to brick red with sugar, and Biuret reagent turns purple with protein.
Different graphs show data in various ways: histograms for height, bar charts for categories like tongue rolling, and scatter graphs for experiments.
Health Warning: Passive smoking affects non-smokers too - there's no safe level of smoke exposure!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
The ethanol test for fats involves adding ethanol then water - a cloudy white colour indicates fat presence. These tests are essential for understanding nutrition and diet.
Creating an onion slide teaches basic microscopy skills. You'll peel the epidermis, add water and iodine, then carefully place a cover slip before observing under the microscope.
These practical skills help you see cell structures clearly and understand how different nutrients affect our bodies.
Lab Tip: Always lower cover slips slowly using a mounted needle to avoid air bubbles!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Your nucleus contains 46 chromosomes arranged in 23 pairs. These thread-like structures are made of DNA, which contains genes that code for your characteristics.
Genes are like instruction manuals written in DNA that determine everything from eye colour to height. They're passed from parents to children during reproduction.
Continuous variation shows gradual differences (like height), whilst discontinuous variation creates clear categories (like blood type). Both types make every person unique!
Mind-Blowing: If you stretched out all the DNA in one cell, it would be about 2 metres long!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Testing energy content in food involves burning samples under water and measuring temperature change. Different foods release different amounts of energy when burned.
A balanced diet means getting the right amounts of all seven food groups. Your energy requirements depend on age, job, activity level, and health status.
Understanding nutrition helps you make better food choices and explains why different people need different amounts of energy throughout their lives.
Personal Connection: Athletes need more energy than desk workers - your lifestyle directly affects your nutritional needs!
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.
1
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
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
Sociology