Provide a brief overview of the five-kingdom classification proposed by $R$.$H$. Whittaker.

(N/A) $R$.$H$. Whittaker $(1969)$ proposed the five-kingdom classification system based on criteria such as cell structure,body organization,mode of nutrition,reproduction,and phylogenetic relationships.
$1$. Kingdom $Monera$: Includes unicellular prokaryotes like bacteria. They are the most abundant microorganisms.
$2$. Kingdom $Protista$: Includes unicellular eukaryotes. They form a link with plants,animals,and fungi.
$3$. Kingdom $Fungi$: Includes heterotrophic,eukaryotic organisms that absorb nutrients from organic matter. They have cell walls made of chitin.
$4$. Kingdom $Plantae$: Includes multicellular,autotrophic,eukaryotic organisms that perform photosynthesis.
$5$. Kingdom $Animalia$: Includes multicellular,heterotrophic,eukaryotic organisms that lack cell walls and ingest food.