Invertebrate

An invertebrate is any animal that does not have a backbone or spinal column. This group includes most animals on earth—over 95% of all known species are invertebrates. They come in many shapes and sizes, from tiny insects to large creatures like octopuses and jellyfish. Because they lack bones, invertebrates often have other structures to support their bodies, such as shells, exoskeletons, or water pressure inside their bodies.

Invertebrates live almost everywhere, from the deepest parts of the ocean to dry deserts and even inside soil. They include many groups such as insects, spiders, worms, mollusks (like snails and squids), and crustaceans (like crabs and lobsters). Some invertebrates, such as corals and sponges, live fixed in one place, while others move quickly to find food or escape danger.

Many invertebrates have unique ways to protect themselves. Insects may use camouflage to blend into their surroundings, while crabs have hard exoskeletons for defense. jellyfish float with soft, flexible bodies but have stinging cells to catch prey. These adaptations help them survive in different habitats and make them a very diverse group of animals.

Unlike vertebrates, which have an internal skeleton, invertebrates use different body systems for movement and protection. For example, worms move by squeezing their muscles, and snails slide on a layer of slime. Insects and crustaceans have jointed legs that let them crawl, fly, or swim. Some invertebrates, such as octopuses, can change color to hide or signal to others.

Invertebrates play important roles in nature. Bees and butterflies pollinate flowers, helping plants grow and make fruits. Earthworms loosen and enrich the soil, allowing plants to take in nutrients. In the ocean, plankton and shellfish form the base of the food chain, feeding larger animals. Without invertebrates, many ecosystems could not function properly.

Scientists divide invertebrates into many groups, or phyla, based on how their bodies are built. These groups include arthropods, mollusks, annelids, cnidarians, and echinoderms. Each group has its own special features, but they all share one key trait: none of them have a backbone. Studying invertebrates helps humans understand evolution, biology, and how life adapts to different environments.