Genetic variation refers to the differences in DNA sequences among individuals within a population. It’s the foundation of evolution by natural selection, providing the raw material for adaptation and species diversity. In IB Biology, understanding how genetic variation arises is essential to explain how populations evolve and respond to environmental pressures.
Quick Start Checklist for IB Biology Students
- Define genetic variation and explain its biological significance
- Learn the three main sources: mutation, meiosis, and sexual reproduction
- Understand how allele frequency changes drive evolution
- Practice data-based questions on population genetics
- Review these concepts using RevisionDojo’s IB Biology learning platform
1. Mutations: The Original Source of Variation
A mutation is a permanent change in the DNA sequence of an organism. Mutations can occur spontaneously during DNA replication or be induced by environmental factors such as radiation and chemicals.
- Point mutations change one base in a gene, sometimes altering a protein’s function.
- Insertions or deletions can shift the genetic reading frame.
- Chromosomal mutations may involve larger-scale structural changes.
While many mutations are neutral or harmful, some are beneficial and provide a selective advantage. Over generations, these beneficial mutations can spread throughout a population, driving evolutionary adaptation.
2. Meiosis: Creating New Combinations of Alleles
During meiosis, gametes (sperm and eggs) are formed, and this process introduces variation through:
- Crossing over (prophase I): Homologous chromosomes exchange segments, creating new allele combinations.
- Independent assortment (metaphase I): Chromosomes align randomly, producing genetically unique gametes.
These mechanisms ensure that no two gametes — and therefore no two offspring — are genetically identical, except in cases of identical twins or clones. This explains the genetic diversity seen in sexually reproducing populations.
3. Sexual Reproduction: Mixing Genes from Two Parents
When gametes combine during fertilization, they produce offspring with a unique set of genes inherited from both parents. This reshuffling of alleles increases genetic diversity within a population. Sexual reproduction allows for new trait combinations, which can help species adapt to changing environments.
This process also plays a key role in IB Biology’s Evolution and Inheritance topics, as it directly influences natural selection, adaptation, and speciation.
Why Genetic Variation Matters
Genetic variation enhances a population’s ability to survive environmental changes. Populations with high genetic diversity are more resilient to disease, climate fluctuations, and habitat shifts. Conversely, low variation — often due to inbreeding or small population size — can lead to genetic disorders and extinction risk.
In the IB Biology curriculum, students must interpret graphs showing allele frequency shifts and understand the role of genetic variation in evolutionary theory and population genetics.
RevisionDojo and IB Biology Mastery
Through RevisionDojo’s IB Biology course, students can explore mutation case studies, meiosis diagrams, and genetic cross simulations. These resources help clarify complex processes while preparing students for data-based and extended-response exam questions.
FAQs
What are the three main causes of genetic variation?
Mutation, meiosis, and sexual reproduction — each introduces new combinations of genes or alleles into a population.
Why is genetic variation important for evolution?
It provides the diversity needed for natural selection to act upon. Without variation, species cannot adapt or evolve over time.
How does meiosis increase genetic variation?
Through crossing over and independent assortment, meiosis produces unique gametes that lead to genetically distinct offspring.
