2.Dear reader, the video is a little lower. Life within the kingdom Animalia includes an extraordinary variety of multicellular organisms built from eukaryotic cells. Despite their diversity, these organisms share several fundamental biological features. Most obtain nutrients by consuming organic substances, depend on oxygen for respiration, possess muscle cells that make movement possible, and pass through a blastula stage during early embryonic development. Evolutionary studies indicate that every modern animal species ultimately originated from a single ancestral population.
Scientists have identified slightly more than 1.5 million living animal species so far, although this number represents only a portion of the world’s biodiversity. Insects make up the largest share, with around 1.05 million recognized species. Researchers have also described over 85,000 mollusc species and approximately 65,000 vertebrate species. Current estimates suggest that the actual global total may approach 7.77 million species, meaning millions have not yet been discovered or formally classified. The range of animal b.o đy sizes is exceptionally broad. At one end are microscopic organisms measuring about 8.5 micrometres (0.00033 inches), while at the other are giant animals capable of reaching 33.6 metres (110 feet) in length.
