Question

Is hydra a unicellular organism? or is it a multicellular organism?

Answer 1

Hint: Hydra is a genus of small, fresh-water organisms that belongs to the phylum Cnidaria and class Hydrozoa. They are native to temperate and tropical regions. They possess a tubular body and have different sizes. They belong to the Animalia kingdom and some species even indulge in relationships with the unicellular algae.

Complete answer:
Hydra has a tubular and radially symmetric body which is secured by a simple adhesive foot known as the basal disc. Gland cells in the basal disc produce a sticky fluid that accounts for its adhesive
properties.

At the free end of the body is a mouth opening that is surrounded by one to twelve thin, mobile tentacles that are clothed with highly specialised stinging cells called cnidocytes. Cnidocytes contain specialized structures called nematocysts that look like miniature light bulbs with a coiled thread inside. At the narrow outer edge of the cnidocyte is a short trigger hair known as cnidocil. Upon contact with prey, the contents of the nematocyst are discharged, ejecting a thread containing neurotoxins into whatever triggered the release. This is responsible for paralyzing the prey. Therefore, Hydras are multicellular organisms because they have a tubular body and have different sizes.

The diagram below depicts a Hydra:

Note: Hydras have two significant structures on their body which are the head and the foot. When a Hydra is cut into half, each half can regenerate and form into a small Hydra. The head will regenerate a foot and the foot regenerates ahead. If the Hydra is sliced into many segments then the middle slices can form both a head and a foot.