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Responding to change (a2 only)
Infection and response
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Organisms respond to changes in their internal and external environments (a-level only)
Biological molecules
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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
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Biology
25 Dec 2025
527
9 pages
Hibaq Gamadid @hecate
Ever wondered how bacteria become resistant to antibiotics, or how scientists create crops that resist pests? This topic... Show more
Variation is what makes every organism slightly different from others in their species - think about how no two people look exactly the same! This variation comes from two main sources mutations (changes in genes) and environmental factors like diet or climate.
There are two types of variation you need to know. Continuous variation has no distinct categories and can be measured, like height or weight. Discontinuous variation falls into clear categories, such as blood type or eye colour.
This variation is actually brilliant for species survival. When environments change or new diseases appear, some individuals might have just the right characteristics to survive and pass on their advantageous genes to the next generation.
Key Point Variation + environmental pressure = evolution in action!
Natural selection is nature's way of choosing which characteristics help organisms survive best. Darwin's theory explains this through a simple process individuals with the most suitable traits for their environment survive longer, breed more successfully, and pass these helpful characteristics to their offspring.
This process is often called "survival of the fittest" - but "fittest" doesn't mean strongest! It means best adapted to the current environment. Over many generations, beneficial traits become more common in the population whilst less useful ones disappear.
Evolution is the gradual change in species over time through natural selection. Darwin proposed that all life forms started simple and gradually became more complex through this process.
Remember Evolution isn't about individual animals changing - it's about populations changing over many generations!
Scientists have found loads of evidence to support evolution, starting with antibiotic resistance in bacteria. When antibiotics are overused, some bacteria survive due to random mutations that make them resistant. These "super bacteria" like MRSA then multiply rapidly, creating populations that our medicines can't kill.
Fossils provide another strong piece of evidence. Simple organisms appear in older rock layers, whilst more complex creatures are found in newer rocks. This shows life gradually becoming more sophisticated over millions of years.
Unfortunately, there are gaps in the fossil record because many early life forms were soft-bodied and didn't preserve well. Geological activity has also destroyed many potential fossils over time.
Exam Tip Always mention that fossil evidence has limitations due to preservation issues!
Stone tools show human evolution in action. Primitive flint axes from 2.5 million years ago gradually developed into sophisticated arrowheads and farming tools. This progression demonstrates how human capabilities and intelligence evolved over time.
The pentadactyl limb is perhaps the most convincing evidence for evolution. Despite looking completely different, the limbs of humans, bats, whales, horses, and birds all share the same basic five-digit bone structure.
This similarity suggests these animals all evolved from a common ancestor, with natural selection modifying the limb for different purposes - flying, swimming, running, or grasping.
Cool Fact Your arm has the same basic bone pattern as a bat's wing and a whale's flipper!
Genetic engineering (also called genetic modification) involves moving genes from one species to another to create organisms with desired characteristics. Scientists use this technique to produce medicines like insulin and create crops that resist pests or diseases.
The process starts with restriction enzymes cutting out specific genes, leaving "sticky ends" - short sections of unpaired DNA bases. A vector (usually a bacterial plasmid) is cut with the same enzyme, creating complementary sticky ends.
The gene and vector are joined using an enzyme called ligase, then inserted into target cells during early development. This allows organisms to grow with completely new characteristics they never had naturally.
Key Process Cut gene → Cut vector → Join with ligase → Insert into target cells
Genetic engineering offers amazing benefits, especially for developing countries. It creates crops with higher yields, better nutritional content, and natural resistance to pests. This technology works much faster than traditional selective breeding methods.
However, there are serious concerns to consider. Some people believe interfering with nature is ethically wrong, whilst others worry about unknown health effects. Genetically modified crops can trigger allergic reactions in sensitive individuals.
Environmental risks include the possibility that modified genes might harm beneficial insects or spread to wild plant populations. The high cost of GM crops can also prevent poor farmers from accessing these potentially life-saving technologies.
Debate Point Weigh the potential to feed millions against unknown long-term consequences!
Selective breeding is humanity's original genetic modification technique - choosing organisms with desirable traits and breeding them together over many generations. Unlike genetic engineering, this method only works with characteristics that already exist in the species.
The process is straightforward but time-consuming. First, select parent organisms with the desired characteristics and breed them together. Choose offspring that show the best traits and breed these together. Repeat this process over many generations until the entire population has the desired characteristics.
For example, to create roses with large pink flowers, a gardener would select the largest, pinkest roses available, breed them together, then continue selecting and breeding the best offspring for several generations.
Remember Selective breeding only enhances existing traits - it can't create completely new ones like genetic engineering can!
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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Explore the principles of natural selection, genetic variation, and genetic modification in this comprehensive study note. Covering key concepts such as recombinant DNA, selective breeding, and the classification of species, this resource is essential for GCSE Edexcel Biology students. Understand how evolution shapes biodiversity and the role of biotechnology in agriculture and medicine.
BiologyExplore the key concepts of genetic variation, natural selection, mutation, selective breeding, and genetic engineering. This summary is tailored for GCSE combined science students, providing essential insights into how these processes shape the diversity of life and influence evolution.
BiologyExplore the fundamentals of selective breeding, including its definition, detailed process, advantages such as improved yield and desirable traits, and disadvantages like inbreeding and health issues. This summary provides essential insights for students studying genetics and agriculture.
BiologyFull notes on topic 6, except punnet squares
BiologyExplore key concepts in genetics, inheritance, and evolution with this comprehensive summary. Understand selective breeding, cloning, genetic engineering, and the impact of mutations on species. Ideal for GCSE Biology AQA students, this resource covers essential topics like natural selection, genetic variation, and the Linnaean classification system.
BiologyExplore the fundamentals of genetic engineering, including the six key steps in gene transfer, advantages and disadvantages, and real-world applications such as insulin production and stem cell research. This summary provides essential insights for students studying biotechnology and genetics.
BiologyApp 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
Hibaq Gamadid
@hecate
Ever wondered how bacteria become resistant to antibiotics, or how scientists create crops that resist pests? This topic explores the fascinating world of genetic variation, natural selection, and how humans manipulate genetics for our benefit.
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Variation is what makes every organism slightly different from others in their species - think about how no two people look exactly the same! This variation comes from two main sources: mutations (changes in genes) and environmental factors like diet or climate.
There are two types of variation you need to know. Continuous variation has no distinct categories and can be measured, like height or weight. Discontinuous variation falls into clear categories, such as blood type or eye colour.
This variation is actually brilliant for species survival. When environments change or new diseases appear, some individuals might have just the right characteristics to survive and pass on their advantageous genes to the next generation.
Key Point: Variation + environmental pressure = evolution in action!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Natural selection is nature's way of choosing which characteristics help organisms survive best. Darwin's theory explains this through a simple process: individuals with the most suitable traits for their environment survive longer, breed more successfully, and pass these helpful characteristics to their offspring.
This process is often called "survival of the fittest" - but "fittest" doesn't mean strongest! It means best adapted to the current environment. Over many generations, beneficial traits become more common in the population whilst less useful ones disappear.
Evolution is the gradual change in species over time through natural selection. Darwin proposed that all life forms started simple and gradually became more complex through this process.
Remember: Evolution isn't about individual animals changing - it's about populations changing over many generations!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Scientists have found loads of evidence to support evolution, starting with antibiotic resistance in bacteria. When antibiotics are overused, some bacteria survive due to random mutations that make them resistant. These "super bacteria" like MRSA then multiply rapidly, creating populations that our medicines can't kill.
Fossils provide another strong piece of evidence. Simple organisms appear in older rock layers, whilst more complex creatures are found in newer rocks. This shows life gradually becoming more sophisticated over millions of years.
Unfortunately, there are gaps in the fossil record because many early life forms were soft-bodied and didn't preserve well. Geological activity has also destroyed many potential fossils over time.
Exam Tip: Always mention that fossil evidence has limitations due to preservation issues!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Stone tools show human evolution in action. Primitive flint axes from 2.5 million years ago gradually developed into sophisticated arrowheads and farming tools. This progression demonstrates how human capabilities and intelligence evolved over time.
The pentadactyl limb is perhaps the most convincing evidence for evolution. Despite looking completely different, the limbs of humans, bats, whales, horses, and birds all share the same basic five-digit bone structure.
This similarity suggests these animals all evolved from a common ancestor, with natural selection modifying the limb for different purposes - flying, swimming, running, or grasping.
Cool Fact: Your arm has the same basic bone pattern as a bat's wing and a whale's flipper!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Genetic engineering (also called genetic modification) involves moving genes from one species to another to create organisms with desired characteristics. Scientists use this technique to produce medicines like insulin and create crops that resist pests or diseases.
The process starts with restriction enzymes cutting out specific genes, leaving "sticky ends" - short sections of unpaired DNA bases. A vector (usually a bacterial plasmid) is cut with the same enzyme, creating complementary sticky ends.
The gene and vector are joined using an enzyme called ligase, then inserted into target cells during early development. This allows organisms to grow with completely new characteristics they never had naturally.
Key Process: Cut gene → Cut vector → Join with ligase → Insert into target cells
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Genetic engineering offers amazing benefits, especially for developing countries. It creates crops with higher yields, better nutritional content, and natural resistance to pests. This technology works much faster than traditional selective breeding methods.
However, there are serious concerns to consider. Some people believe interfering with nature is ethically wrong, whilst others worry about unknown health effects. Genetically modified crops can trigger allergic reactions in sensitive individuals.
Environmental risks include the possibility that modified genes might harm beneficial insects or spread to wild plant populations. The high cost of GM crops can also prevent poor farmers from accessing these potentially life-saving technologies.
Debate Point: Weigh the potential to feed millions against unknown long-term consequences!
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Improve your grades
Join milions of students
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Selective breeding is humanity's original genetic modification technique - choosing organisms with desirable traits and breeding them together over many generations. Unlike genetic engineering, this method only works with characteristics that already exist in the species.
The process is straightforward but time-consuming. First, select parent organisms with the desired characteristics and breed them together. Choose offspring that show the best traits and breed these together. Repeat this process over many generations until the entire population has the desired characteristics.
For example, to create roses with large pink flowers, a gardener would select the largest, pinkest roses available, breed them together, then continue selecting and breeding the best offspring for several generations.
Remember: Selective breeding only enhances existing traits - it can't create completely new ones like genetic engineering can!
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Access to all documents
Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
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.
19
Smart Tools NEW
Transform this note into: ✓ 50+ Practice Questions ✓ Interactive Flashcards ✓ Full Mock Exam ✓ Essay Outlines
Explore the principles of natural selection, genetic variation, and genetic modification in this comprehensive study note. Covering key concepts such as recombinant DNA, selective breeding, and the classification of species, this resource is essential for GCSE Edexcel Biology students. Understand how evolution shapes biodiversity and the role of biotechnology in agriculture and medicine.
BiologyExplore the key concepts of genetic variation, natural selection, mutation, selective breeding, and genetic engineering. This summary is tailored for GCSE combined science students, providing essential insights into how these processes shape the diversity of life and influence evolution.
BiologyExplore the fundamentals of selective breeding, including its definition, detailed process, advantages such as improved yield and desirable traits, and disadvantages like inbreeding and health issues. This summary provides essential insights for students studying genetics and agriculture.
BiologyFull notes on topic 6, except punnet squares
BiologyExplore key concepts in genetics, inheritance, and evolution with this comprehensive summary. Understand selective breeding, cloning, genetic engineering, and the impact of mutations on species. Ideal for GCSE Biology AQA students, this resource covers essential topics like natural selection, genetic variation, and the Linnaean classification system.
BiologyExplore the fundamentals of genetic engineering, including the six key steps in gene transfer, advantages and disadvantages, and real-world applications such as insulin production and stem cell research. This summary provides essential insights for students studying biotechnology and genetics.
BiologyApp 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