Phylum Arthropoda (Part 1)
Welcome to the world of arthropods - the most successful animals on Earth! This massive group includes insects, spiders, crustaceans, centipedes, and more, making up over 80% of all known animal species. Their success comes from several amazing adaptations that have allowed them to colonize virtually every habitat.
Arthropods have bilateral symmetry, three tissue layers, and a coelom. They have well-developed nervous systems with a brain, nerve cord, ganglia, and sophisticated sense organs. Their most distinctive features include specialized body segments (typically organized into head, thorax, and abdomen), a protective exoskeleton made of chitin, and jointed appendages that can be modified for walking, swimming, feeding, or sensing.
The exoskeleton provides protection and prevents water loss, but it creates a challenge: it can't grow with the animal. That's why arthropods must periodically molt - shedding their old exoskeleton and growing a new, larger one. This process allows for growth but leaves them temporarily vulnerable to predators.
Mind-Blowing Scale: If you combined all humans on Earth, we'd weigh about 287 million tons. The world's ants alone weigh about 700 million tons! Arthropods truly dominate our planet.