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Levels of Organisation and the Digestive System
Think of your body like a company with five levels of management, each building on the last. Cells are your basic workers, whilst tissues are teams of similar cells doing the same job. Organs are departments where different tissues collaborate, and organ systems are divisions where organs work together. Finally, the whole organism (that's you!) is when everything functions as one unit.
Your digestive system is brilliant teamwork in action. Your mouth starts the process by chewing, whilst salivary glands release amylase enzymes to begin breaking down starch. The stomach churns food and releases acid to kill harmful bacteria, plus protease enzymes to digest proteins.
The liver and pancreas are your chemical factories. The liver makes bile (stored in the gall bladder) to neutralise stomach acid and break fat into tiny droplets. Meanwhile, the pancreas produces three key enzymes: amylase, lipase, and protease to digest different food types.
Quick Tip: Remember that the small intestine absorbs nutrients whilst the large intestine absorbs water - don't mix them up in your exams!
The Respiratory System
Breathing might seem simple, but there's actually a sophisticated pathway air takes through your body. When you breathe in, air travels through your mouth and nose, down the trachea (windpipe), splits into two bronchi, then branches into smaller bronchioles, and finally reaches tiny alveoli (air sacs).
The magic happens at the alveoli, where oxygen diffuses into your bloodstream through a network of capillaries. These air sacs are perfectly designed for gas exchange - they're incredibly thin and have a huge surface area.
Breathing out is controlled by your diaphragm and intercostal muscles. When these muscles relax, your diaphragm moves up and your ribcage drops inwards and downwards. This increases pressure in your lungs, forcing air out naturally.
Exam Focus: Learn the breathing pathway in order - examiners love testing this sequence from trachea to alveoli!
The Circulatory System and Blood Vessels
Your blood is actually a tissue made of four crucial components working as a team. Red blood cells are oxygen taxis, carrying it around your body. Plasma is the liquid highway that transports everything. Platelets are your emergency repair crew, forming clots when you're injured. White blood cells are your security team, fighting off infections and pathogens.
Blood vessels have structures perfectly matched to their jobs. Arteries carry blood away from your heart under high pressure, so they need thick, muscular walls to cope. Veins return blood to your heart at low pressure, which is why they have valves to prevent backflow and thinner walls.
Capillaries are the delivery network - just one cell thick so oxygen and nutrients can easily diffuse to your tissues. They connect arteries and veins, completing the circuit.
Memory Trick: Arteries = Away from the heart. Both start with 'A'!
The Heart and Double Circulation
Your heart is a muscular pump made of cardiac muscle that never gets tired. It has four chambers working in pairs: the right ventricle pumps blood to your lungs, whilst the left ventricle (which is stronger) pumps blood around your entire body.
Key heart structures include the aorta (carries oxygenated blood to your body), vena cava (brings deoxygenated blood back), pulmonary artery (takes blood to lungs), and pulmonary vein (brings oxygenated blood from lungs). Your heart rate is controlled by special cells in the right atrium that work like a natural pacemaker.
Humans have a double circulatory system because blood passes through your heart twice in every complete circuit. This is incredibly efficient - the right side sends blood to your lungs for oxygen, whilst the left side pumps that freshly oxygenated blood to the rest of your body.
Exam Success: Remember that the left ventricle has thicker walls because it needs more power to pump blood around your entire body, not just to the nearby lungs!
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Thomas R
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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
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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
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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
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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
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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
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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
Animal Organization in Biology for High School: Key Notes
Your body is like a perfectly organised city with different levels working together - from tiny cells all the way up to complete organ systems. Understanding how your digestive, respiratory, and circulatory systems are structured will help you ace your... Show more
Levels of Organisation and the Digestive System
Think of your body like a company with five levels of management, each building on the last. Cells are your basic workers, whilst tissues are teams of similar cells doing the same job. Organs are departments where different tissues collaborate, and organ systems are divisions where organs work together. Finally, the whole organism (that's you!) is when everything functions as one unit.
Your digestive system is brilliant teamwork in action. Your mouth starts the process by chewing, whilst salivary glands release amylase enzymes to begin breaking down starch. The stomach churns food and releases acid to kill harmful bacteria, plus protease enzymes to digest proteins.
The liver and pancreas are your chemical factories. The liver makes bile (stored in the gall bladder) to neutralise stomach acid and break fat into tiny droplets. Meanwhile, the pancreas produces three key enzymes: amylase, lipase, and protease to digest different food types.
Quick Tip: Remember that the small intestine absorbs nutrients whilst the large intestine absorbs water - don't mix them up in your exams!
Sign up to see the contentIt's free!
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Improve your grades
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By signing up you accept Terms of Service and Privacy Policy
The Respiratory System
Breathing might seem simple, but there's actually a sophisticated pathway air takes through your body. When you breathe in, air travels through your mouth and nose, down the trachea (windpipe), splits into two bronchi, then branches into smaller bronchioles, and finally reaches tiny alveoli (air sacs).
The magic happens at the alveoli, where oxygen diffuses into your bloodstream through a network of capillaries. These air sacs are perfectly designed for gas exchange - they're incredibly thin and have a huge surface area.
Breathing out is controlled by your diaphragm and intercostal muscles. When these muscles relax, your diaphragm moves up and your ribcage drops inwards and downwards. This increases pressure in your lungs, forcing air out naturally.
Exam Focus: Learn the breathing pathway in order - examiners love testing this sequence from trachea to alveoli!
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The Circulatory System and Blood Vessels
Your blood is actually a tissue made of four crucial components working as a team. Red blood cells are oxygen taxis, carrying it around your body. Plasma is the liquid highway that transports everything. Platelets are your emergency repair crew, forming clots when you're injured. White blood cells are your security team, fighting off infections and pathogens.
Blood vessels have structures perfectly matched to their jobs. Arteries carry blood away from your heart under high pressure, so they need thick, muscular walls to cope. Veins return blood to your heart at low pressure, which is why they have valves to prevent backflow and thinner walls.
Capillaries are the delivery network - just one cell thick so oxygen and nutrients can easily diffuse to your tissues. They connect arteries and veins, completing the circuit.
Memory Trick: Arteries = Away from the heart. Both start with 'A'!
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The Heart and Double Circulation
Your heart is a muscular pump made of cardiac muscle that never gets tired. It has four chambers working in pairs: the right ventricle pumps blood to your lungs, whilst the left ventricle (which is stronger) pumps blood around your entire body.
Key heart structures include the aorta (carries oxygenated blood to your body), vena cava (brings deoxygenated blood back), pulmonary artery (takes blood to lungs), and pulmonary vein (brings oxygenated blood from lungs). Your heart rate is controlled by special cells in the right atrium that work like a natural pacemaker.
Humans have a double circulatory system because blood passes through your heart twice in every complete circuit. This is incredibly efficient - the right side sends blood to your lungs for oxygen, whilst the left side pumps that freshly oxygenated blood to the rest of your body.
Exam Success: Remember that the left ventricle has thicker walls because it needs more power to pump blood around your entire body, not just to the nearby lungs!
We thought you’d never ask...
What is the Knowunity AI companion?
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.
Where can I download the Knowunity app?
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Is Knowunity really free of charge?
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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