Q.Explain stabilizing, directional and disruptive selection with examples.

Step 1. Stabilising selection (centripetal selection) operates in a stable environment: individuals with average phenotypes survive and reproduce, while individuals from both extremes are eliminated, so the population's variation narrows over generations without any new species forming. Example: measurements of sparrows that survived a severe storm clustered around the population mean body size, while the sparrows that died were disproportionately from the size extremes.

Step 2. Directional selection operates when the environment is gradually changing: it removes individuals from one end of the phenotype range, progressively shifting the whole population's distribution toward the other end. Example: male and female sparrows look externally alike but differ in body weight, with females showing a directional shift relative to males. …

Define each of the three selection types by which part of the phenotype distribution is favoured/elimina …

• Mixing up directional and disruptive selection — directional shifts toward ONE end, disruptive splits toward BOTH ends. …