Which of the following is a synapomorphy for mammals? a)Lactation b)Limbs c)Circulatory system d)Amniotic egg

Evolution is defined as a slow gradual change over a period of time. It brings about the deviation of species. Organic evolution is a slow, gradual, and continuous change due to which complex organisms are formed today from simple pre-existing forms. There are various theories proposed for the process of evolution. It is necessary to classify the organisms into various groups based on some characteristics. There are various methods for the classification of organisms. The organisms are classified on the basis of shared traits in a system called cladistics. If a trait exists in two organisms and is present in their common ancestor it is called a clade. 

• Synapomorphy- A shared character between the ancestor and its descendants is called synapomorphy. All the mammals share a characteristic of producing milk which is an example of synapomorphy