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8 Jan 2026
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AQA GCSE Biology Topic 6: Inheritance, Variation & Evolution Notes
H
heather
@heatherwu
1 / 5
Reproduction and DNA Basics
Ever wondered how you ended up with your mum's eyes but your dad's nose? It all comes down to meiosis - the special process that creates gametes (sex cells like sperm and eggs). Unlike normal cell division, meiosis creates four genetically different cells, each with half the usual number of chromosomes.
Sexual reproduction needs two parents and creates loads of variation, which helps species survive through natural selection. Asexual reproduction only needs one parent and is much faster - think of how quickly bacteria multiply when you're ill!
Your DNA is basically a twisted ladder (called a double helix) made from four different bases that pair up: C with G, and A with T. Every sequence of three bases codes for one amino acid, and these amino acids link together to make proteins through protein synthesis.
Quick tip: Remember that your genotype is the genetic code you carry, whilst your phenotype is what actually shows up - like having the gene for brown eyes (genotype) and actually having brown eyes (phenotype).
Genetic Disorders and Natural Selection
Some genetic conditions are caused by dominant alleles (like polydactyly, where you're born with extra fingers), whilst others need recessive alleles from both parents (like cystic fibrosis). This is why Punnett squares are so useful - they help predict what characteristics offspring might inherit.
Evolution happens when populations change over time through natural selection. Here's how it works: individuals show variation, those best suited to their environment survive and reproduce more, and they pass their advantageous alleles to their offspring.
Selective breeding lets humans speed up this process by choosing parents with desirable traits. Farmers use this to create disease-resistant crops or cows that produce more milk. However, it can lead to inbreeding, making organisms more vulnerable to diseases.
Remember: A species is defined as organisms that can reproduce together to produce fertile offspring - which is why horses and donkeys are different species (their offspring, mules, are infertile).
Genetic Engineering and Cloning
Genetic engineering sounds like science fiction, but it's happening right now! Scientists can take genes from one organism and put them into another to create desired characteristics. For example, bacteria can be modified to produce human insulin for diabetics.
The process involves using restriction enzymes to cut out specific genes, inserting them into plasmids (tiny DNA circles in bacteria), then using ligase to seal everything together. The modified bacteria then multiply, creating loads of the desired product.
Cloning comes in several forms. Tissue culture and cuttings help preserve rare plants, whilst embryo transplants split early animal embryos before cells specialise. Adult cell cloning is the most complex - scientists remove the nucleus from an unfertilised egg and replace it with a nucleus from an adult cell.
Fascinating fact: Dolly the sheep was created using adult cell cloning, proving that even specialised adult cells contain all the genetic information needed to create a whole organism!
Evolution Scientists and Fossils
Charles Darwin changed everything with his theory of evolution by natural selection, published in "On the Origin of Species". His ideas took time to be accepted because they challenged religious beliefs, lacked sufficient evidence, and scientists didn't yet understand how inheritance worked.
Speciation occurs when populations become geographically separated and face different environmental pressures. Over time, mutations and natural selection cause so many changes that the groups can no longer interbreed - creating new species.
Gregor Mendel discovered the basic principles of inheritance through his plant breeding experiments, showing that characteristics are passed down in distinct "units" (what we now call genes). Fossils provide evidence of evolution, forming when organisms don't fully decay, when minerals replace bones, or when traces like footprints are preserved.
Key point: The fossil record is incomplete because most early organisms were soft-bodied, geological activity destroyed many fossils, and fossilisation requires very specific conditions.
Disease Resistance and Classification
Antibiotics only work against bacteria because they target bacterial cell walls - but viruses don't have cell walls, which is why antibiotics can't cure viral infections like colds. Unfortunately, antibiotic resistance is becoming a major problem as bacterial mutations create strains that survive antibiotic treatment.
MRSA is a dangerous example of antibiotic-resistant bacteria. To slow the development of resistance, doctors shouldn't prescribe antibiotics for minor infections, patients must complete their full course, and agricultural antibiotic use should be limited.
Scientists classify living things using the Linnaean system: Kingdom, Phylum, Class, Order, Family, Genus, Species. This helps us understand relationships between organisms and gives scientists a common language. Carl Woese later proposed the three-domain system, dividing life into Archaea (primitive bacteria in extreme environments), Bacteria (true bacteria), and Eukaryota (everything else with proper cell nuclei).
Study tip: Remember the classification order with "King Philip Came Over For Good Soup" - it's a classic memory trick that actually works!
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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.
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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.
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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
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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
AQA GCSE Biology Topic 6: Inheritance, Variation & Evolution Notes
H
heather
@heatherwu
Ready to dive into the fascinating world of genetics and evolution? This topic covers everything from how your cells create the next generation to why Darwin's ideas revolutionised science - and it's more relevant to your daily life than you... Show more
Reproduction and DNA Basics
Ever wondered how you ended up with your mum's eyes but your dad's nose? It all comes down to meiosis - the special process that creates gametes (sex cells like sperm and eggs). Unlike normal cell division, meiosis creates four genetically different cells, each with half the usual number of chromosomes.
Sexual reproduction needs two parents and creates loads of variation, which helps species survive through natural selection. Asexual reproduction only needs one parent and is much faster - think of how quickly bacteria multiply when you're ill!
Your DNA is basically a twisted ladder (called a double helix) made from four different bases that pair up: C with G, and A with T. Every sequence of three bases codes for one amino acid, and these amino acids link together to make proteins through protein synthesis.
Quick tip: Remember that your genotype is the genetic code you carry, whilst your phenotype is what actually shows up - like having the gene for brown eyes (genotype) and actually having brown eyes (phenotype).
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Genetic Disorders and Natural Selection
Some genetic conditions are caused by dominant alleles (like polydactyly, where you're born with extra fingers), whilst others need recessive alleles from both parents (like cystic fibrosis). This is why Punnett squares are so useful - they help predict what characteristics offspring might inherit.
Evolution happens when populations change over time through natural selection. Here's how it works: individuals show variation, those best suited to their environment survive and reproduce more, and they pass their advantageous alleles to their offspring.
Selective breeding lets humans speed up this process by choosing parents with desirable traits. Farmers use this to create disease-resistant crops or cows that produce more milk. However, it can lead to inbreeding, making organisms more vulnerable to diseases.
Remember: A species is defined as organisms that can reproduce together to produce fertile offspring - which is why horses and donkeys are different species (their offspring, mules, are infertile).
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
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Genetic Engineering and Cloning
Genetic engineering sounds like science fiction, but it's happening right now! Scientists can take genes from one organism and put them into another to create desired characteristics. For example, bacteria can be modified to produce human insulin for diabetics.
The process involves using restriction enzymes to cut out specific genes, inserting them into plasmids (tiny DNA circles in bacteria), then using ligase to seal everything together. The modified bacteria then multiply, creating loads of the desired product.
Cloning comes in several forms. Tissue culture and cuttings help preserve rare plants, whilst embryo transplants split early animal embryos before cells specialise. Adult cell cloning is the most complex - scientists remove the nucleus from an unfertilised egg and replace it with a nucleus from an adult cell.
Fascinating fact: Dolly the sheep was created using adult cell cloning, proving that even specialised adult cells contain all the genetic information needed to create a whole organism!
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Evolution Scientists and Fossils
Charles Darwin changed everything with his theory of evolution by natural selection, published in "On the Origin of Species". His ideas took time to be accepted because they challenged religious beliefs, lacked sufficient evidence, and scientists didn't yet understand how inheritance worked.
Speciation occurs when populations become geographically separated and face different environmental pressures. Over time, mutations and natural selection cause so many changes that the groups can no longer interbreed - creating new species.
Gregor Mendel discovered the basic principles of inheritance through his plant breeding experiments, showing that characteristics are passed down in distinct "units" (what we now call genes). Fossils provide evidence of evolution, forming when organisms don't fully decay, when minerals replace bones, or when traces like footprints are preserved.
Key point: The fossil record is incomplete because most early organisms were soft-bodied, geological activity destroyed many fossils, and fossilisation requires very specific conditions.
Sign up to see the contentIt's free!
Access to all documents
Improve your grades
Join milions of students
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Disease Resistance and Classification
Antibiotics only work against bacteria because they target bacterial cell walls - but viruses don't have cell walls, which is why antibiotics can't cure viral infections like colds. Unfortunately, antibiotic resistance is becoming a major problem as bacterial mutations create strains that survive antibiotic treatment.
MRSA is a dangerous example of antibiotic-resistant bacteria. To slow the development of resistance, doctors shouldn't prescribe antibiotics for minor infections, patients must complete their full course, and agricultural antibiotic use should be limited.
Scientists classify living things using the Linnaean system: Kingdom, Phylum, Class, Order, Family, Genus, Species. This helps us understand relationships between organisms and gives scientists a common language. Carl Woese later proposed the three-domain system, dividing life into Archaea (primitive bacteria in extreme environments), Bacteria (true bacteria), and Eukaryota (everything else with proper cell nuclei).
Study tip: Remember the classification order with "King Philip Came Over For Good Soup" - it's a classic memory trick that actually works!
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?
You can download the app from Google Play Store and Apple App Store.
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