Assertion : Appetency is the formation of new structure or habit of the organism according to its need. Reason : Appetency is also called doctrine of desire.

Step-by-step solution

According to Lamarck, a change in environment brings about changes in organisms. It gives rise to new needs. New needs or desires produce new structures and change habits of the organisms. Doctrine of desire is called appetency. It can be shown by the following example- Water birds (duck etc.) developed their webbed feet by constant stretching of digits and the skin between them for skimming the water surface and for swimming. The transmission of acquired characters is the most important principle usually termed as