Question

Which of the following animals carry out both intra and extracellular digestion?
A) Cnidarians
B) Flatworms
C) Proto-chordates
D) All of the above

Answer 1

Hint: Intracellular digestion occurs inside the body while extracellular digestion occurs outside the body. Cnidarians and flatworms do not have a complete digestive system. Protochordates are closely related to vertebrates. They have a complete digestive system.

Complete answer:
Digestion is the process by which food breaks into simpler substances. It can be of two types: intracellular and intercellular. In intracellular digestion breakdown of substances occurs within the cytoplasm of the cell. They involve phagocytosis for engulfing the substances inside the cell. This process can occur with the help of lysosomes and food vacuoles.
Extracellular digestion takes place outside the cell. Enzymes are involved in this process for the breakdown of food into small molecules.
Cnidarians perform extracellular digestion. All the digestion processes completed in the intracellular region. Food absorbed in the gastrovascular cavity and nutrients absorbed by the cell lining of the cavity.
Flatworms have conspicuous digestive systems. It consists of the mouth, pharynx and intestine. They uses intracellular digestion. It takes the food in by phagocytosis. Cnidarians and flatworms both have incomplete digestive systems.
Proto-chordates include both urochordates and cephalochordates. The digestion in these organisms occurs both inside and outside the cell. They are closely related to the vertebrates. They also have dorsal nerve cord.
From the above information we have found that proto-chordates carry out both intra and extracellular digestion.

So, the correct answer is option C.

Note: Cnidarians include Scyphozoa (jellyfish), Cubozoa (box jellies), hydroids, anemones and corals. Flukes, planaria, turbellaria, and tapeworms are some examples of flatworms. Some of the examples of proto-chordates are amphioxus, salpa, doliolum, and saccoglossus.