Question

In which group of organisms, the cell walls form two thin overlapping shells which fit together?
A.Slime molds
B.Chrysophyte
C.Euglenoids
D.Dinoflagellates

Answer 1

Cell wall is present in the plant and not in the animal cell. This makes a clarified distinction between the two types of cells. The plant cell wall has three layers, namely primary cell wall, secondary cell wall, and middle lamella.

Complete answer:
Option A) Slime molds are a part of Kingdom Protista. The plasmodial slime molds have one cellular membrane, not covered by another wall or a membrane and the most are a bag of cytoplasm. The cellular slime molds are unicellular protists and they live on dead material.
Option B) Chrysophytes are marine or freshwater protists and include species like diatoms, golden/golden-brown algae, and yellow-green algae. Different species of this phylum have different compositions of cell structure. However, the cell wall of chrysophytes has chitin and a large amount of silica which makes a very hard and thickening layering that is hard to break. Some amoeboids do not have a cell wall. The species in this phylum have one or two flagella. They store their food in the form of oils or polysaccharide laminarin.
Option C) Euglenoids do not possess a cell wall but have chloroplast. Instead of a cell wall, Euglenoids have a pellicle made of a protein layer and supported by microtubules. The unique flexibility and contractility of the euglena is because the pellicle strips that are spiraled around the cell slide over one another. Euglena forms a cell wall in the dormant stage.
Option D) Dinoflagellates have the cell walls that form two thin overlapping shells that fit together. They have a soapy-box like a cell wall that is siliceous. They possess a membrane-bound cell wall called theca.

Hence the correct answer is option D.

Note:
Parent Dinoflagellates shed a part of their cell wall during reproduction. Some species of Dinoflagellates have a cyst cell wall that cannot fossilize.