Question

Identify the correct statement about the organisms spongilla, Leech, Dolphin, and Penguin.
A) Leech is freshwater while others are marine.
B) Spongilla has special collared cells called choanocytes while it is not found in the other three.
C) All are bilaterally symmetrical.
D) Penguin is homoeothermic while the meaning three is poikilothermic.

Answer 1

Hint: It is an aquatic organism that has a feature that is unique to it and is not found in any other organism. The biosphere contains different organisms which live in freshwater or marine habitat but there are some which acquire both the habitats. Other organisms are either cold-blooded or warm-blooded.

Complete answer:
> Spongilla belongs to the phylum Porifera which includes sponges. Spongilla is a freshwater sponge and not a marine water sponge.
> Spongilla is asymmetrical and not radially symmetrical.
> Spongilla is a sponge so it is devoid of the blood vascular system.
> Spongilla acquires freshwater habitat so it is aquatic and so they have a cell layer known as choanoderm which is further lined by cells known as choanocytes. These are flagellated cells and they are present in the collar region of sponges, they help in filtering nutrients from the water. These are unique to sponges only.

Let’s have a further look at other options:
> Leech (belonging to Annelida) is not just freshwater but inhabits both marine and freshwater habitats while we already know that spongilla is freshwater and Penguin and dolphins are marine.
> Only Spongilla is asymmetrical( the body is not differentiated into equal planes) while all the others are bilaterally symmetrical( the opposite sides are similar).
> Spongilla is devoid of blood. Leech is poikilothermic i.e. Cold-blooded and Dolphin and Penguin are Homeothermic i.e. Warm-blooded.

Spongilla has special collared cells called Choanocytes while it is not found in the other three. So, the correct answer is option B. As we know that every organism is unique and acquires different habitats.

Note: Every organism in the biosphere is unique with regards to specific features and are hence placed in different phyla accordingly.
> Leech belongs to the phylum Annelida.
> Dolphin belongs to the phylum chordate and is a mammal.
> Penguin belongs to Chordata and is a bird, not a mammal.