Animals are best described as
Animals are best defined as multicellular eukaryotic heterotrophs whose cells lack rigid cell walls, exhibiting internal digestion within gastrovascular cavity or gut lumen, active motility and complex development from zygote through holoblastic cleavage forming morula, blastula and gastrula with germ layers. Diploid dominance, collagenous extracellular matrix, excitable neurons and muscle effectors characterize clade. Contrasts with unicellular autotrophs like Euglena, colonial photosynthetic Volvox and prokaryotic organisms lacking true nucleus, membrane organelles and linear chromosome orga
Ref: NCERT Class 11 Biology Chapter 4 Animal Kingdom General Characters; Campbell Biology 12th ed. Chapter 32 Definition of Animals