variety of life Flashcards
homology
the living organisms of a particular group which have similar characters are known as homology
order of taxonomy
↷ kingdom ↷ phylum ↷ class ↷ order ↷ family ↷ genus ↷ specie
viruses
virus are not placed in any of the five kingdoms because they only contain protein coat and nucleic acid. they’re also non-cellular bodies and considered between living and non-living
they can only reproduce inside a living organism. absence of cell wall, cytoplasm, nucleus, and chromosomes
structure of virus and describe what they contain (capsid, viral envelopes.etc. )
they are rounded, rod-shape, tadpole like or polyhedral. they consist of few parts::
!! viral genome:: it is the inner part, the nucleic acid. it consists of many molecules of DNA or RNA
!! capsid:: the central part genome // nucleic acid of virus is covered by a protein coat known as capsid. the capsid is made up of numerous protein units called capsomeres.
!! viral envelopes:: this is the membranous covering around the capsid. it helps them to infect their hosts
!! tail fibres:: at the posterior end of tail, some fibre like structures are present, called tail fibres. these fibres take part in the attachment of virus with host cell
structure of bacteriophage
bacteriophage is a bacterial virus. it consists of two parts:: head and tail.
彡 head ,, tail :: head contains a core of DNA (nucleic acid) and is covered by capsid. the tail is also covered by a proteineous layer. from the lower end of bacteriophage, some fibrous structures are produced which help in attachment of virus into the host bacterial cell
classification of viruses (unenveloped plus-strand RNA viruses)
these viruses contain nucleic acid surrounded by capsid but their outer envelope is absent.
these viruses perform the function of m-RNA after infecting the host cell. they’re attached to ribosomes. they’re plus stranded
enveloped plus-strand RNA viruses
these viruses have envelope outside their capsid. this envelope is made up of lipids. they attack vertebrates and arthropodes
minus strand RNA viruses
they carry the RNA strand to the m-RNA, so they’re considered as the minus strand. they’ve envelopes
viroids
they do not have capsid. they consist of circular molecules of RNA
double strand RNA virus
they contain double strand of RNA molecules with capsid and envelopes
small-genome DNA viruses
they’ve small genome. some contain DNA with single strand and some have two strands. these viruses also have envelopes
medium-genome // large-genome DNA viruses
they’ve medium or large genome, with double stranded DNA. they also have envelopes
bacteriophage
these viruses attack bacteria
life cycle of bacteriophage (lytic cycle)
ೃ the reproductive cycle of virus which causes death of the bacterial cell is called lytic cycle.
ೃ the virus first attaches to the bacterial cell by its protein tail. lysozyme is secreted by the tail which helps to dissolve the bacterial cell wall
ೃ the DNA of virus is transferred into the bacterial cell from the head region and the protein coat of the head and tail remains outside
ೃ inside the bacterial cell ,, the viral DNA then controls the bacterial cell activity. the duplication of the viral DNA takes place and the new phage particles start to produce inside the cell
ೃ the DNA of the virus is migrated into the head portion
ೃ after some time, the bacterial cell bursts and new bacteriophage are set free
advantages // disadvantages of viruses
๑ they cause diseases in man and in other animals
๑ they attack economically important plants
๑ phages maybe harmful in industries which utilize bacterial action
๑ phages help in transferring genetic material from one bacterium to another
