Give reason, "Unicellular organism can ingest through cell surface but multicellular organism needs digestive system."
Answers
Unicellular organisms such as yeast undergo differentiation in the form of morphological changes, accompanied by metabolic adaptation. These organisms can sense the amount and type of nutrients in the environment and alter gene expression patterns to maximize survival. Multiple signaling pathways interact to bring about changes in gene expression. For induction of filamentation, it appears that the metabolic adaptations result in changes in glutathione redox states but do not necessarily correlate with changes in ATP generation. Although the precise relationship is not clear, OXPHOS and functional respiratory chain appears critical for filamentation induction.
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in an organism (it may be unicellular or multicellular ) all its cells needs nutrient to function normally
for unicellular organism cell can take nutrient from their cell surface
but the presence of digestive system becomes necessary in multicellular organism
one more reason the organism who ingest through cell surface ingest the simplest or simpler food so its only need simple digestuion which can take place within the cell