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3 Dec 2025
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Understanding Inheritance, Variation, and Evolution
Charlotte
@charlotte26
1 / 5
Asexual and Sexual Reproduction
You'll encounter two completely different ways that organisms reproduce, and understanding both is crucial for your exams. Asexual reproduction uses mitosis with just one parent, creating identical copies called clones.
During mitosis, the cell grows larger, duplicates its DNA, and makes more organelles. Then the genetic material separates, and finally the cytoplasm splits to form two identical daughter cells. It's like biological photocopying!
Sexual reproduction is far more complex, involving meiosis to create gametes (sex cells). First, chromosomes duplicate in a diploid cell, then similar chromosomes pair up and swap genes - this gene shuffling creates the variation that makes you unique.
Quick Check: Remember that asexual = identical offspring, sexual = varied offspring!
From Gametes to Genes
The meiosis process continues by dividing twice - first creating two diploid cells, then four haploid gametes that are all genetically different. This variation is evolution's secret weapon, helping species adapt and survive.
Fertilisation happens when male and female gametes fuse together. In animals, that's sperm meeting egg; in plants, it's pollen meeting egg cell. Females have XX chromosomes whilst males have XY.
Now for the key terminology that'll appear in every genetics question. Your genome is your entire genetic code, made of DNA (that famous double helix). Genes are specific portions that code for proteins, whilst your genotype is the genetic code itself and your phenotype is how those genes actually appear in your physical characteristics.
Alleles are simply different versions of the same gene - think of them as different flavours of the same recipe.
Genetic Inheritance Patterns
Punnett squares are your best friend for predicting inheritance - they're like genetic calculators that show all possible offspring combinations. You'll need to master these for exam success.
Dominant alleles (written as capital letters) always show up in your phenotype - you only need one copy. Recessive alleles (lowercase letters) need two copies to be expressed, which is why they often skip generations.
Cystic fibrosis demonstrates recessive inheritance perfectly. It affects lungs and digestion, causing sticky mucus that can be life-threatening. Parents are usually carriers (Ff) who don't show symptoms but can pass the faulty allele to their children.
Polydactyly (extra fingers or toes) shows dominant inheritance - you only need one dominant allele to have this condition.
Exam Tip: Remember that carriers (heterozygous) have one working and one faulty allele!
Genetic Testing and Engineering
Genetic screening analyses DNA to spot alleles that cause disorders, and it happens at different life stages. Antenatal testing checks before birth, whilst neonatal testing (the heel prick test) screens newborns for genetic conditions.
Gene therapy involves inserting normal alleles into people with faulty ones. Scientists identify the problem gene, cut out healthy versions using restriction enzymes, make copies, then insert them into affected cells.
The pros include reducing suffering and potentially saving money on treatments. However, there are serious ethical concerns - it might suggest people with genetic disorders are somehow 'undesirable', and false results can cause unnecessary worry.
Genetic engineering transfers genes between organisms to create desired characteristics. The classic example is bacteria engineered to produce human insulin for diabetes treatment. Antibiotic resistance occurs when bacteria randomly mutate to survive antibiotic treatment.
Evolution and Classification
Mutations are spontaneous changes in genes or chromosomes that create new characteristics. If these changes help survival, they'll be passed on to future generations through natural selection.
Variation comes from three sources: purely genetic (like blood type), purely environmental (like language), or a combination of both (like height). This variation provides the raw material for evolution.
Fossils preserve organisms from thousands of years ago through mineralisation, casts, impressions, or direct preservation. They're our window into evolution's history and support Darwin's theory of natural selection - 'survival of the fittest'.
Scientists classify life using two main systems. Linnaeus's system from the 1700s uses Kingdom, Phylum, Class, Order, Genus, Species. Woese's three-domain system from 1990 groups everything into Archaea (primitive bacteria), Bacteria (true bacteria), and Eukaryota (complex cells).
Memory Trick: For classification levels, remember "King Philip Came Over For Good Soup"!
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4.9/5
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4.8/5
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
Understanding Inheritance, Variation, and Evolution
Charlotte
@charlotte26
Ever wondered why you look like your parents but not exactly like them? This topic explores how living things reproduce and pass on their characteristics, from the basics of cell division to how evolution shapes all life on Earth.
Asexual and Sexual Reproduction
You'll encounter two completely different ways that organisms reproduce, and understanding both is crucial for your exams. Asexual reproduction uses mitosis with just one parent, creating identical copies called clones.
During mitosis, the cell grows larger, duplicates its DNA, and makes more organelles. Then the genetic material separates, and finally the cytoplasm splits to form two identical daughter cells. It's like biological photocopying!
Sexual reproduction is far more complex, involving meiosis to create gametes (sex cells). First, chromosomes duplicate in a diploid cell, then similar chromosomes pair up and swap genes - this gene shuffling creates the variation that makes you unique.
Quick Check: Remember that asexual = identical offspring, sexual = varied offspring!
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
From Gametes to Genes
The meiosis process continues by dividing twice - first creating two diploid cells, then four haploid gametes that are all genetically different. This variation is evolution's secret weapon, helping species adapt and survive.
Fertilisation happens when male and female gametes fuse together. In animals, that's sperm meeting egg; in plants, it's pollen meeting egg cell. Females have XX chromosomes whilst males have XY.
Now for the key terminology that'll appear in every genetics question. Your genome is your entire genetic code, made of DNA (that famous double helix). Genes are specific portions that code for proteins, whilst your genotype is the genetic code itself and your phenotype is how those genes actually appear in your physical characteristics.
Alleles are simply different versions of the same gene - think of them as different flavours of the same recipe.
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
Genetic Inheritance Patterns
Punnett squares are your best friend for predicting inheritance - they're like genetic calculators that show all possible offspring combinations. You'll need to master these for exam success.
Dominant alleles (written as capital letters) always show up in your phenotype - you only need one copy. Recessive alleles (lowercase letters) need two copies to be expressed, which is why they often skip generations.
Cystic fibrosis demonstrates recessive inheritance perfectly. It affects lungs and digestion, causing sticky mucus that can be life-threatening. Parents are usually carriers (Ff) who don't show symptoms but can pass the faulty allele to their children.
Polydactyly (extra fingers or toes) shows dominant inheritance - you only need one dominant allele to have this condition.
Exam Tip: Remember that carriers (heterozygous) have one working and one faulty allele!
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
Genetic Testing and Engineering
Genetic screening analyses DNA to spot alleles that cause disorders, and it happens at different life stages. Antenatal testing checks before birth, whilst neonatal testing (the heel prick test) screens newborns for genetic conditions.
Gene therapy involves inserting normal alleles into people with faulty ones. Scientists identify the problem gene, cut out healthy versions using restriction enzymes, make copies, then insert them into affected cells.
The pros include reducing suffering and potentially saving money on treatments. However, there are serious ethical concerns - it might suggest people with genetic disorders are somehow 'undesirable', and false results can cause unnecessary worry.
Genetic engineering transfers genes between organisms to create desired characteristics. The classic example is bacteria engineered to produce human insulin for diabetes treatment. Antibiotic resistance occurs when bacteria randomly mutate to survive antibiotic treatment.
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
Evolution and Classification
Mutations are spontaneous changes in genes or chromosomes that create new characteristics. If these changes help survival, they'll be passed on to future generations through natural selection.
Variation comes from three sources: purely genetic (like blood type), purely environmental (like language), or a combination of both (like height). This variation provides the raw material for evolution.
Fossils preserve organisms from thousands of years ago through mineralisation, casts, impressions, or direct preservation. They're our window into evolution's history and support Darwin's theory of natural selection - 'survival of the fittest'.
Scientists classify life using two main systems. Linnaeus's system from the 1700s uses Kingdom, Phylum, Class, Order, Genus, Species. Woese's three-domain system from 1990 groups everything into Archaea (primitive bacteria), Bacteria (true bacteria), and Eukaryota (complex cells).
Memory Trick: For classification levels, remember "King Philip Came Over For Good Soup"!
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?
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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Most popular content in Biology
Most popular content
English - inspector calls quotes and analysis
Quotes from every main character
English Literature10
Can't find what you're looking for? Explore other subjects.
Students love us — and so will you.
4.9/5
App Store
4.8/5
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