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hannah
27/11/2025
Biology
B6~ inheritance, variation & evolution
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27 Nov 2025
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B6 Inheritance, Variation, and Evolution Study Guide
hannah
@hannah_qhgof
1 / 7
DNA and Genetic Basics
Ever wondered why you've got your dad's nose or your gran's curly hair? It all comes down to DNA - the chemical blueprint stored in long molecules called chromosomes. Think of DNA as a massive instruction manual that determines every inherited characteristic you have.
Genes are like individual recipes within this manual. Each gene is a small section of DNA that codes for a specific protein by arranging amino acids in particular sequences. With just 20 different amino acids, your body creates thousands of unique proteins!
Your genome is your complete genetic collection - like having every recipe book ever written just for you. Scientists studying the human genome can now identify disease-linked genes and trace how populations migrated across the globe.
Key Point: Understanding your genome is like having a personalised health manual - it helps predict inherited diseases and develop targeted treatments.
Sexual vs Asexual Reproduction
Reproduction comes in two main flavours, and each has massive consequences for genetic diversity. Sexual reproduction combines genetic material from two parents through fertilisation - when an egg and sperm fuse together. Each parent contributes 23 chromosomes through gametes (sex cells), creating offspring with a full set of 46 chromosomes.
This mixing creates variation - why siblings aren't identical (unless they're twins). It's nature's way of ensuring species can adapt and survive changing environments.
Asexual reproduction tells a completely different story. With only one parent involved, offspring are genetic clones - identical copies created through mitosis. No gamete fusion means no chromosome mixing and zero variation.
Remember This: Sexual reproduction = variation and adaptability. Asexual reproduction = quick colonisation but vulnerability to diseases.
Meiosis and Genetic Diagrams
Meiosis is the special cell division that creates gametes with exactly half the normal chromosome number. It's like shuffling a deck of cards - chromosomes get mixed up randomly, ensuring each gamete is genetically unique.
The process involves chromosome pairs lining up, separating, then dividing again. This produces four genetically different gametes from one original cell. When fertilisation occurs, mitosis takes over to build the embryo through repeated cell divisions.
Genetic diagrams help predict inheritance patterns using alleles - different versions of the same gene. You inherit two alleles for each characteristic (one from each parent). Dominant alleles (shown as capital letters) mask recessive alleles (lowercase letters). Your genotype is your allele combination, whilst your phenotype is the actual characteristic you display.
Quick Tip: Remember - you need two recessive alleles to show a recessive trait, but only one dominant allele to show a dominant trait.
Variation, Evolution and Natural Selection
Mutations are random DNA changes that create new genetic variants. Most mutations barely affect you, but occasionally they dramatically alter characteristics - like causing cystic fibrosis through faulty salt and water transport proteins.
Natural selection drives evolution through "survival of the fittest." Organisms best suited to their environment survive, reproduce, and pass on beneficial genes. Over generations, these advantageous characteristics become common throughout the species.
Speciation occurs when populations change so much they can't interbreed anymore - essentially becoming new species. Meanwhile, extinction happens when species can't adapt fast enough to environmental changes, new diseases, or competition.
Evolution Insight: It's not about being strongest or fastest - it's about being best adapted to your specific environment.
Selective Breeding and Genetic Engineering
Selective breeding lets humans play evolution - choosing organisms with desirable traits and breeding them together over generations. Farmers use this to increase milk production, improve disease resistance, or develop gentler temperaments in animals.
However, selective breeding reduces the gene pool (available genetic diversity). This inbreeding increases risks of genetic defects and makes populations vulnerable to new diseases.
Genetic engineering takes a more direct approach - transferring specific genes between organisms using vectors like viruses or bacterial plasmids. Scientists have created bacteria producing human insulin, crops resistant to herbicides, and sheep producing medicinal compounds in their milk.
Breeding Balance: Selective breeding improves desired traits but genetic engineering offers precision - though both raise important ethical questions about manipulating life.
Fossils and Antibiotic Resistance
Fossils provide crucial evidence for evolution - showing how organisms looked millions of years ago and how they've changed. They form through mineral replacement, casts in hardened clay, or preservation in amber, ice, or acidic peat bogs where decay can't occur.
Antibiotic-resistant bacteria demonstrate evolution in action. Random mutations occasionally make bacteria less affected by antibiotics. Since bacteria reproduce rapidly, resistant strains quickly dominate populations when antibiotics kill off non-resistant competitors.
MRSA represents a dangerous "superbug" - resistant to most known antibiotics and particularly threatening in hospitals. Overuse and misuse of antibiotics accelerates this resistance, whilst incomplete antibiotic courses leave surviving bacteria to develop further resistance.
Resistance Reality: Taking your full antibiotic course isn't just good advice - it's crucial for preventing the next generation of superbugs.
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B6 Inheritance, Variation, and Evolution Study Guide
hannah
@hannah_qhgof
DNA and genetics might seem complex, but they're actually the fascinating instructions that make you unique! From how you inherit your mum's eyes to why some bacteria resist antibiotics, understanding genetics helps explain the incredible diversity of life around us.
DNA and Genetic Basics
Ever wondered why you've got your dad's nose or your gran's curly hair? It all comes down to DNA - the chemical blueprint stored in long molecules called chromosomes. Think of DNA as a massive instruction manual that determines every inherited characteristic you have.
Genes are like individual recipes within this manual. Each gene is a small section of DNA that codes for a specific protein by arranging amino acids in particular sequences. With just 20 different amino acids, your body creates thousands of unique proteins!
Your genome is your complete genetic collection - like having every recipe book ever written just for you. Scientists studying the human genome can now identify disease-linked genes and trace how populations migrated across the globe.
Key Point: Understanding your genome is like having a personalised health manual - it helps predict inherited diseases and develop targeted treatments.
Sign up to see the contentIt's free!
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Improve your grades
Join milions of students
By signing up you accept Terms of Service and Privacy Policy
Sexual vs Asexual Reproduction
Reproduction comes in two main flavours, and each has massive consequences for genetic diversity. Sexual reproduction combines genetic material from two parents through fertilisation - when an egg and sperm fuse together. Each parent contributes 23 chromosomes through gametes (sex cells), creating offspring with a full set of 46 chromosomes.
This mixing creates variation - why siblings aren't identical (unless they're twins). It's nature's way of ensuring species can adapt and survive changing environments.
Asexual reproduction tells a completely different story. With only one parent involved, offspring are genetic clones - identical copies created through mitosis. No gamete fusion means no chromosome mixing and zero variation.
Remember This: Sexual reproduction = variation and adaptability. Asexual reproduction = quick colonisation but vulnerability to diseases.
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Meiosis and Genetic Diagrams
Meiosis is the special cell division that creates gametes with exactly half the normal chromosome number. It's like shuffling a deck of cards - chromosomes get mixed up randomly, ensuring each gamete is genetically unique.
The process involves chromosome pairs lining up, separating, then dividing again. This produces four genetically different gametes from one original cell. When fertilisation occurs, mitosis takes over to build the embryo through repeated cell divisions.
Genetic diagrams help predict inheritance patterns using alleles - different versions of the same gene. You inherit two alleles for each characteristic (one from each parent). Dominant alleles (shown as capital letters) mask recessive alleles (lowercase letters). Your genotype is your allele combination, whilst your phenotype is the actual characteristic you display.
Quick Tip: Remember - you need two recessive alleles to show a recessive trait, but only one dominant allele to show a dominant trait.
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Variation, Evolution and Natural Selection
Mutations are random DNA changes that create new genetic variants. Most mutations barely affect you, but occasionally they dramatically alter characteristics - like causing cystic fibrosis through faulty salt and water transport proteins.
Natural selection drives evolution through "survival of the fittest." Organisms best suited to their environment survive, reproduce, and pass on beneficial genes. Over generations, these advantageous characteristics become common throughout the species.
Speciation occurs when populations change so much they can't interbreed anymore - essentially becoming new species. Meanwhile, extinction happens when species can't adapt fast enough to environmental changes, new diseases, or competition.
Evolution Insight: It's not about being strongest or fastest - it's about being best adapted to your specific environment.
Sign up to see the contentIt's free!
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By signing up you accept Terms of Service and Privacy Policy
Selective Breeding and Genetic Engineering
Selective breeding lets humans play evolution - choosing organisms with desirable traits and breeding them together over generations. Farmers use this to increase milk production, improve disease resistance, or develop gentler temperaments in animals.
However, selective breeding reduces the gene pool (available genetic diversity). This inbreeding increases risks of genetic defects and makes populations vulnerable to new diseases.
Genetic engineering takes a more direct approach - transferring specific genes between organisms using vectors like viruses or bacterial plasmids. Scientists have created bacteria producing human insulin, crops resistant to herbicides, and sheep producing medicinal compounds in their milk.
Breeding Balance: Selective breeding improves desired traits but genetic engineering offers precision - though both raise important ethical questions about manipulating life.
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Fossils and Antibiotic Resistance
Fossils provide crucial evidence for evolution - showing how organisms looked millions of years ago and how they've changed. They form through mineral replacement, casts in hardened clay, or preservation in amber, ice, or acidic peat bogs where decay can't occur.
Antibiotic-resistant bacteria demonstrate evolution in action. Random mutations occasionally make bacteria less affected by antibiotics. Since bacteria reproduce rapidly, resistant strains quickly dominate populations when antibiotics kill off non-resistant competitors.
MRSA represents a dangerous "superbug" - resistant to most known antibiotics and particularly threatening in hospitals. Overuse and misuse of antibiotics accelerates this resistance, whilst incomplete antibiotic courses leave surviving bacteria to develop further resistance.
Resistance Reality: Taking your full antibiotic course isn't just good advice - it's crucial for preventing the next generation of superbugs.
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We thought you’d never ask...
What is the Knowunity AI companion?
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Where can I download the Knowunity app?
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Xander S
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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
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Best app on earth! no words because it’s too good
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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.
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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.
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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.
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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 😍😁😲🤑💗✨🎀😮
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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
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