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3 Jan 2026
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GCSE Biology Notes: Understanding Diseases
Nila Heartin
@nilaheartin_tmsl
1 / 4
What Are Pathogens and How Do They Make You Ill?
Your body faces constant attacks from four main types of pathogens - disease-causing organisms that want to make you their home. Viruses are basically genetic material wrapped in protein, whilst bacteria have cell walls but no proper nucleus. Protists are a mixed bag of unicellular organisms, and fungi look like plant cells but without chloroplasts.
Once these invaders get inside you, they multiply rapidly - and that's when you start feeling rough. Bacteria pump out nasty toxins that poison your body, whilst viruses are even sneakier. They hijack your host cells, turning them into virus factories before destroying them completely.
Those classic symptoms like fever and rashes? They're partly caused by pathogen damage, but also by your body's own response to the invasion. It's like your immune system is having a proper fight, and you're caught in the crossfire.
Quick Tip: Remember that symptoms come from both the pathogen's damage AND your body's response to it!
How Diseases Spread and Semmelweis's Discovery
Diseases spread in four main ways, and knowing these helps you avoid getting ill. Air droplet infection happens when someone coughs or sneezes near you - those tiny droplets are packed with pathogens. Contaminated water can deliver pathogens straight to your gut, whilst direct contact through skin or sexual contact spreads many diseases.
Ignaz Semmelweis was a Hungarian doctor who figured out something revolutionary in the 1800s. He noticed that when doctors washed their hands before treating patients, fewer people died from puerperal fever. Sounds obvious now, right?
Unfortunately, other doctors weren't having it. They thought handwashing was too time-consuming and didn't want to accept responsibility for all those deaths. Poor Semmelweis spent 14 years trying to convince people, wrote a book, then died before anyone properly listened to him.
Remember This: Semmelweis pioneered antiseptic policy - his ideas about cleanliness now save millions of lives!
Common Infectious Diseases You Need to Know
Measles is a viral nightmare that spreads through coughs and sneezes. After 10-12 days, you'll get fever, runny nose, and those telltale white spots inside your cheeks. The rash then spreads everywhere, but vaccines can prevent it entirely.
HIV attacks your immune system through infected body fluids, eventually leading to AIDS. It's not curable, but antiretroviral therapy (ART) helps people live longer, healthier lives.
Salmonella bacterial infection comes from dodgy food - especially undercooked eggs and meat. You'll get diarrhoea, fever, and stomach cramps, but antibiotics and plenty of fluids sort you out.
Gonorrhoea is a sexually transmitted bacterial infection causing painful urination and discharge. A single antibiotic dose usually clears it up, but using condoms prevents it entirely.
Exam Tip: Learn the pathogen type, transmission method, symptoms, and treatment for each disease - they love testing these!
Plant Diseases and Malaria
Plants get ill too! Rose Black Spot is a fungal disease creating purple-black spots on leaves, which then turn yellow and drop off. This reduces photosynthesis, stunting the plant's growth. Fungicides treat it, but prevention involves removing infected leaves and avoiding watering the leaves directly.
Tobacco Mosaic Virus (TMV) spreads through contaminated hands and tools, creating that distinctive mosaic pattern on leaves. Burn infected material and disinfect everything to stop it spreading.
Malaria is caused by protists carried by female mosquitoes - these insects are called vectors. You'll get fever, vomiting, and diarrhoea, and it can be fatal. Anti-malarial drugs work in early stages, but prevention is better: use mosquito nets, repellent, and remove stagnant water where mosquitoes breed.
Key Point: Vectors like mosquitoes don't cause disease themselves - they just transport the pathogens that do!
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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.
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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!
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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
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
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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
GCSE Biology Notes: Understanding Diseases
Nila Heartin
@nilaheartin_tmsl
Ever wondered how diseases spread and why you get ill? Understanding pathogens and how your body fights them off is crucial for staying healthy and doing well in your biology exams.
What Are Pathogens and How Do They Make You Ill?
Your body faces constant attacks from four main types of pathogens - disease-causing organisms that want to make you their home. Viruses are basically genetic material wrapped in protein, whilst bacteria have cell walls but no proper nucleus. Protists are a mixed bag of unicellular organisms, and fungi look like plant cells but without chloroplasts.
Once these invaders get inside you, they multiply rapidly - and that's when you start feeling rough. Bacteria pump out nasty toxins that poison your body, whilst viruses are even sneakier. They hijack your host cells, turning them into virus factories before destroying them completely.
Those classic symptoms like fever and rashes? They're partly caused by pathogen damage, but also by your body's own response to the invasion. It's like your immune system is having a proper fight, and you're caught in the crossfire.
Quick Tip: Remember that symptoms come from both the pathogen's damage AND your body's response to it!
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How Diseases Spread and Semmelweis's Discovery
Diseases spread in four main ways, and knowing these helps you avoid getting ill. Air droplet infection happens when someone coughs or sneezes near you - those tiny droplets are packed with pathogens. Contaminated water can deliver pathogens straight to your gut, whilst direct contact through skin or sexual contact spreads many diseases.
Ignaz Semmelweis was a Hungarian doctor who figured out something revolutionary in the 1800s. He noticed that when doctors washed their hands before treating patients, fewer people died from puerperal fever. Sounds obvious now, right?
Unfortunately, other doctors weren't having it. They thought handwashing was too time-consuming and didn't want to accept responsibility for all those deaths. Poor Semmelweis spent 14 years trying to convince people, wrote a book, then died before anyone properly listened to him.
Remember This: Semmelweis pioneered antiseptic policy - his ideas about cleanliness now save millions of lives!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Common Infectious Diseases You Need to Know
Measles is a viral nightmare that spreads through coughs and sneezes. After 10-12 days, you'll get fever, runny nose, and those telltale white spots inside your cheeks. The rash then spreads everywhere, but vaccines can prevent it entirely.
HIV attacks your immune system through infected body fluids, eventually leading to AIDS. It's not curable, but antiretroviral therapy (ART) helps people live longer, healthier lives.
Salmonella bacterial infection comes from dodgy food - especially undercooked eggs and meat. You'll get diarrhoea, fever, and stomach cramps, but antibiotics and plenty of fluids sort you out.
Gonorrhoea is a sexually transmitted bacterial infection causing painful urination and discharge. A single antibiotic dose usually clears it up, but using condoms prevents it entirely.
Exam Tip: Learn the pathogen type, transmission method, symptoms, and treatment for each disease - they love testing these!
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Plant Diseases and Malaria
Plants get ill too! Rose Black Spot is a fungal disease creating purple-black spots on leaves, which then turn yellow and drop off. This reduces photosynthesis, stunting the plant's growth. Fungicides treat it, but prevention involves removing infected leaves and avoiding watering the leaves directly.
Tobacco Mosaic Virus (TMV) spreads through contaminated hands and tools, creating that distinctive mosaic pattern on leaves. Burn infected material and disinfect everything to stop it spreading.
Malaria is caused by protists carried by female mosquitoes - these insects are called vectors. You'll get fever, vomiting, and diarrhoea, and it can be fatal. Anti-malarial drugs work in early stages, but prevention is better: use mosquito nets, repellent, and remove stagnant water where mosquitoes breed.
Key Point: Vectors like mosquitoes don't cause disease themselves - they just transport the pathogens that do!
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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Most popular content: Pathogen
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4.9/5
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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