Arthropoda is a large group of invertebrate animals that includes insects, spiders, crabs, and centipedes. These creatures are characterized by their jointed legs, segmented bodies, and exoskeletons made of chitin. They are found in nearly every habitat on Earth, from deep oceans to high mountains, showcasing their incredible adaptability. One of the most fascinating aspects of arthropods is their diversity. There are over a million known species, making them the largest phylum in the animal kingdom. This group plays essential roles in ecosystems, such as pollination by bees and decomposition by millipedes, highlighting their importance in maintaining ecological balance.