Members of the same species can look very different when they live in different environments. The phenotype of an organism results from the interaction of its genotype and the environment. Differences between populations may therefore be caused by the environment, by genetic differences, or by both.Environmental effects
• Hydrangeas: genetically identical plants produce blue flowers in acidic soil, where more aluminium ions are available, and pink flowers in alkaline soil.
• Siamese cats and Himalayan rabbits: an enzyme needed to make dark pigment only works at lower temperatures, so the fur on the cooler parts of the body (ears, paws, nose and tail) is darker.
• Plants of one species grow taller in shade than in full sun.Genetic differences
Populations of one species living in different conditions face different selection pressures. Over many generations, each population may become genetically adapted to its local conditions. Such populations are called ecotypes. For example, yarrow (Achillea) growing at high altitude in the Sierra Nevada is much shorter than yarrow growing near sea level.Telling them apart
To find out whether a difference is genetic or environmental, organisms from different sites are grown together in the same conditions, called a common garden experiment, or swapped between sites (a reciprocal transplant). If high-altitude yarrow stays short even when grown at low altitude, the difference is genetic. If it grows tall like the lowland plants, the difference was caused by the environment.
• Hydrangeas: genetically identical plants produce blue flowers in acidic soil, where more aluminium ions are available, and pink flowers in alkaline soil.
• Siamese cats and Himalayan rabbits: an enzyme needed to make dark pigment only works at lower temperatures, so the fur on the cooler parts of the body (ears, paws, nose and tail) is darker.
• Plants of one species grow taller in shade than in full sun.Genetic differences
Populations of one species living in different conditions face different selection pressures. Over many generations, each population may become genetically adapted to its local conditions. Such populations are called ecotypes. For example, yarrow (Achillea) growing at high altitude in the Sierra Nevada is much shorter than yarrow growing near sea level.Telling them apart
To find out whether a difference is genetic or environmental, organisms from different sites are grown together in the same conditions, called a common garden experiment, or swapped between sites (a reciprocal transplant). If high-altitude yarrow stays short even when grown at low altitude, the difference is genetic. If it grows tall like the lowland plants, the difference was caused by the environment.