BIOLOGY
Chapter: Acellular Life
Study Notes
For Grade: 11
Introduction:
•Evolution reveals that life began on earth from simple molecules like DNA
and protein.
•Acellular or noncellular living things may have originated from fragments of
DNA/RNA that escaped
from living cells.
•They lack intact cells or a living entity.
Viruses either living or non-living:
Virus show dual nature:
Living characters:
•They have their own nucleic acid either DNA
or RNA and can undergo mutations.
,•They can reproduce but only inside a host
cell.
•They cause specific diseases in living
organism .
Non-living characters:
•They have no cellular structure, no cytoplasm, nucleus or organelles.
•They cannot perform respiration, metabolism, or
growth.
•They exist as crystals and cannot reproduce on their own.
Viruses:
Definitions: A virus is a submicroscopic infectious agent made of nucleic acid
(DNA or RNA)
enclosed in a protein coat (capsid).
Structure: It consist of two parts ¡)The outer coat (capsid & envelope) ¡¡)The
inner
core (genome)
, Discovery of Viruses: 1892 – Ivanovsky found a filterable infectious agent in
tobacco plants.
1898 – Beijerinck named it virus “poison”
Example:HIV (AIDS),Influenza virus ,Bacteriophage(infect bacteria )
Classification of viruses:
Virus can be classified on the basis of host or shape or genome.
1.Based on host:
Phytophage (plant viruses ):
•Their genetic material is RNA.
•More than 2000 types.
•E.g. T.M.V ,Potato virus etc
Zoophage ( Animal viruses):
•Their genetic material is DNA or
RNA both.
•E.g. Rabies virus ,Influenza virus
,covid-19 etc.
Chapter: Acellular Life
Study Notes
For Grade: 11
Introduction:
•Evolution reveals that life began on earth from simple molecules like DNA
and protein.
•Acellular or noncellular living things may have originated from fragments of
DNA/RNA that escaped
from living cells.
•They lack intact cells or a living entity.
Viruses either living or non-living:
Virus show dual nature:
Living characters:
•They have their own nucleic acid either DNA
or RNA and can undergo mutations.
,•They can reproduce but only inside a host
cell.
•They cause specific diseases in living
organism .
Non-living characters:
•They have no cellular structure, no cytoplasm, nucleus or organelles.
•They cannot perform respiration, metabolism, or
growth.
•They exist as crystals and cannot reproduce on their own.
Viruses:
Definitions: A virus is a submicroscopic infectious agent made of nucleic acid
(DNA or RNA)
enclosed in a protein coat (capsid).
Structure: It consist of two parts ¡)The outer coat (capsid & envelope) ¡¡)The
inner
core (genome)
, Discovery of Viruses: 1892 – Ivanovsky found a filterable infectious agent in
tobacco plants.
1898 – Beijerinck named it virus “poison”
Example:HIV (AIDS),Influenza virus ,Bacteriophage(infect bacteria )
Classification of viruses:
Virus can be classified on the basis of host or shape or genome.
1.Based on host:
Phytophage (plant viruses ):
•Their genetic material is RNA.
•More than 2000 types.
•E.g. T.M.V ,Potato virus etc
Zoophage ( Animal viruses):
•Their genetic material is DNA or
RNA both.
•E.g. Rabies virus ,Influenza virus
,covid-19 etc.
