This definitions covers Key Definitions within Variation for GCSE Biology. Genetic and environmental variation in organisms It is section 5 of 10 in this topic. Make sure you can use the exact wording confidently, because definition marks are often lost through vague language.
Topic position
Section 5 of 10
Practice
25 questions
Recall
20 flashcards
Key Definitions
Variation: The differences in characteristics between individuals of the same species. Variation can be genetic, environmental, or a combination of both.
Genetic variation: Differences between individuals caused by differences in their inherited DNA sequences (genotype). Examples: blood group, eye colour, inherited disorders.
Environmental variation: Differences between individuals caused by the conditions in which they develop and live. Examples: scars, tanned skin, language spoken, body weight (partly).
Continuous variation: Variation where individuals show a range of values from one extreme to another, with all intermediate values possible. Forms a normal distribution (bell curve). Examples: height, mass, intelligence.
Discontinuous variation: Variation where individuals fall into distinct, separate categories with no intermediate values. Examples: ABO blood group (A, B, AB, O), tongue rolling (can/cannot), sex (male/female).
Mutation: A random change in the DNA base sequence of a gene or chromosome. Mutations can be caused by mutagens (e.g., UV radiation, some chemicals) or occur spontaneously during DNA replication. They are the source of new alleles.
Meiosis: Cell division that produces gametes (sex cells) with half the normal chromosome number. Meiosis generates genetic variation through random chromosome assortment and crossing over between homologous chromosomes.