Question

In the evolution of animals, a heart to pump the blood is found for the first time in

• A. Annelids
• B. Round worms
• C. Arthropods
• D. Flat worms

Answer 1

The correct option is A Annelids

The circulatory system has evolved with the evolution of animals. The heart is the main organ of the circulatory system. The heart varies from being a simple system in invertebrates to more complex system as is found in vertebrates. While the simple animals such as the Sponges (Porifera) do not have a circulatory system as the diffusion allows the exchange of water and nutrients and waste Cnidaria and Ctenophora diffuses through their epidermis and gastrovascular compartment. As the invertebrates become a little more complex they use an open circulatory system with no blood vessels or only a few and blood is pumped throughout all tissues and filters back to the pumping mechanism as is seen in Annelids where there is no heart but makes use of the muscular regions which pumps blood to the tissues. This is the precursor to the human heart.

So, the correct answer is 'Annelids'