Introduction:
The acellular organism is defined as the organism that is not made up of the cells, but still has nucleic acid, and has the ability to replicate within the host cell genome. As acellular organisms do not have a cell so they are not considered as an organism. So, it is better to call them a particle rather than an organism.
Correct answer:
Viruses are the acellular microorganisms lacking a nucleus. Therefore, option (d) is correct.
Option (d) is given as “virus”.
Justify the reasons for the correct statement:
Viruses are the acellular entities that are considered as ultramicroscopic infectious particles, viruses are known to infect all the life forms present or earth, from microbes to plants and animals. Viruses have either DNA or RNA as their genetic materials yet they lack cell organelles. Hence, they are named as acellular organisms.
Hence, option (d) is correct.
Justify the reasons for the incorrect statements:
Option (a) is given as “bacterium”.
Bacteria have a nucleoid region instead of a true nucleus, but they are unicellular organisms means they have a single cell. Hence, it is a wrong answer.
Option (b) is given as “helminth”.
The helminths are the multicellular organisms. And each cell has a well-known nucleus. Hence, it is a wrong answer.
Option (c) is given as “protozoan”.
Protozoa belong to domain eukaryotes but are the unicellular microorganisms. So, they contain a nucleus. Hence, it is a wrong answer.
Hence, options (a),(b), and(c) are incorrect.
Hence, viruses are lacking a nucleus, because they do not have cells organelles. Yet,the virushas a nucleic acid, either DNA or RNA.