Key Characteristics of Major Invertebrate Phyla
Major Invertebrate Phyla
Mollusks
Mollusks are soft-bodied animals whose anatomical plan typically includes a head, a foot, a visceral mass, and a mantle, often secreting an external shell. Notable examples include gastropods, bivalves (characterized by two flexible shells united by a hinge), and cephalopods, marine predators whose foot has evolved into tentacles.
Arthropods
Arthropods are the most abundant animals on the planet. Their body is typically divided into segments, forming a head with sensory and feeding structures, a thorax, and an abdomen. They periodically need to shed their chitinous exoskeleton, which is rigid and does not expand as the animal grows. The main classes are:
- Insects: Possess three pairs of legs and one or two pairs