Causes of Variation Revision Notes | GCSE OCR Foundation Biology

What this lesson covers

Explore how genetic factors, environmental conditions, and their combination create variation in organisms. Learn about genetic diversity in populations...

• Explain how genetic factors cause variation between individuals
• Describe how environmental factors influence organism development
• Analyse examples where both genes and environment interact to produce variation
• Compare genetic variation within populations of the same species

Key ideas to keep in view

Use this lesson to stay inside B5.1 Inheritance while connecting the detail back to the wider B5: Genes, inheritance and selection topic.

• B5: Genes, inheritance and selection
• B5.1 Inheritance
• GCSE OCR Foundation Biology

Lesson notes preview

Read the core explanations from Causes of Variation before testing yourself from memory.

• Look around your classroom. Everyone's different - height, eye colour, hair texture, even how they react to the same joke. This isn't random. There's a scientific explanation for why no two people are identical (except identical twins, and even they aren't completely the same).
• These differences between individuals are called variation. Understanding variation is crucial because it explains everything from why some people are naturally athletic to why certain diseases run in families. It's also the raw material that makes evolution possible.
• Differences in characteristics between individuals in a population. These differences can be physical (like height), behavioural (like personality), or physiological (like blood type).
• But here's where it gets interesting - variation has two main causes, and they work in completely different ways. Sometimes they even fight against each other.
• 2. Genetic Causes - The Blueprint You're Born With
• Your genes are like a detailed instruction manual written in your DNA. They determine many of your characteristics before you're even born. Think of them as the 'factory settings' for your body.
• Differences between organisms caused by different versions of genes (alleles) inherited from parents. These are fixed at fertilisation and cannot be changed by lifestyle or environment.
• Key examples of genetic variation:Blood type - You're born with A, B, AB, or O and it never changesEye colour - Determined by genes controlling melanin productionAbility to roll your tongue - Either you can or you can't, no amount of practice changes thisGenetic disorders - Like cystic fibrosis or sickle cell anaemia
• Trap: Many students think all physical features are genetic. Actually, your final height depends on genes AND nutrition. Your genes set the potential, but environment determines if you reach it.
• 3. Environmental Causes - How Your Surroundings Shape You

Continue through the topic

Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.