Question

What are the characters of dinoflagellates?
1. Planktonic golden yellow algae with soapbox structure
2. Marine red biflagellate protists
3. Appear yellow, green, blue and red
4. The biflagellate organism with pellicle
5. Saprophytic or parasitic unicellular forms.
A. $1,2$ and $3$ only
B. $2,4$ and $5$ only
C. $2$ and $3$ only
D. $2$ and $5$ only
E. $3,4$ and $5$ only

Answer 1

Dinoflagellates are the unicellular organisms of the phylum Dinoflagellata. They have a characteristic cellulosic cell wall. They are of marine habitat and are mostly photosynthetic. Have two flagella one of which is longitudinal in direction and the other is a transverse present between the furrow of the cell plates. The sexual mode of reproduction is seen to be absent.

Complete answer:
Planktonic golden yellow algae with soapbox-like structure is the characteristic of diatoms of the phylum Chrysophyta. Hence the statement $1$ is incorrect.
The organism contains two flagella but the pellicle is not seen. Hence the statement $4$ is incorrect.
Dinoflagellates are unicellular but perform photosynthesis to prepare food so it is an autotrophic organism hence the statement $5$ is incorrect.
Dinoflagellates are marine, contain two flagella, and appear red. Hence the option $2$ is correct.
They appear red, blue, yellow, green depending on the pigment present inside the cell. Hence the statement $3$ is correct.
From the above statements, it can be concluded that – option A is incorrect, option B is incorrect, option D is incorrect and option E is incorrect.

The correct answer is option C. $2$ and $3$ only is correct.

Note:
Dinoflagellates have a cellulosic cell wall that is divided into plates giving an armored-like appearance. The red tide in the ocean is caused by Gonyaulax – a dinoflagellate. The red tide occurs due to the rapid multiplication of dinoflagellates. Fishes are killed by the toxins produced by them, these toxins are known as saxitoxin.