Question

In which of the following organisms, extracellular as well as intracellular digestion occurs?
A) Paramecium
B) Planaria
C) Earthworm
D) All the given options

Answer 1

Hint: All species must receive nutrients from the environment to survive. Digestion is the process of breaking down and chemically converting food to be consumed by an organism's cells and used to sustain essential bodily functions.

Complete answer:
Animals eat by secreting enzymes across the cell membrane onto their food in a process known as extracellular digestion. Food is broken down into molecules which are small enough to move across the cell membrane and through the cell by enzymes. Intracellular digestion also refers to the mechanism by which animals without a digestive tract carry food into the cell to be digested for nutritional purposes.
Food is digested in the food vacuole of Paramecium by digestive enzymes produced by the cytoplasm. In Paramecium, digestion is referred to as intracellular digestion.

Both intracellular and extracellular digestion occurs in planaria. Food is digested in the intestine, and enzymes are secreted by the glands cells of the intestine to begin the extracellular digestion process. Small particles of food are then engulfed by phagocytic vacuoles, and intracellular digestion is completed.

The earthworm's digestive system consists of an alimentary canal that runs the length of the body from mouth to anus, as well as glands. The earthworm, like higher animals like frogs and rabbits, has extracellular digestion. Since Paramecium has intracellular digestion and earthworm has extracellular digestion, we can conclude that option D is also wrong.

Therefore, the answer is Option ‘B’ i.e,Planaria.

Note: The genus Planaria belongs to the Planariidae family of planarians. Planaria torva, a single species found in Europe, is the only one that currently represents it. When the Planaria is cut into pieces, each piece will regenerate into a fully formed one.