Even through some organisms, such as sponges, jellyfish and sea anemones, look like vegetables they belong to the animal kingdom. Many of these simple Invertebrates are unable to move from one place to another. Some even lack certain tissues or an entire respiratory or digestive system.
Other, more developed especially species such as squid and octopus can move about and have become skilled marine predators. Cephalopods are the most highly evolved molluscs. Their heads have highly developed eyes, a mouth with two hornlike jaws, and tentacles with suckers to trap their prey. Some cephalopods live in deep sea waters, whereas others stay close to shore.
Characteristics of Invertebrates
- Many of the numerous invertebrates on the earth live in the ocean.
- Some such as polyps and jellyfish, have radial symmetry. That means their bodies are structured around an axis.
- The animal uses them to hold onto surfaces and to move. Sponges, on the other hand, are very simple, multiple celled animals with many small pores that they used to feed.
- Corals generally form colonies, large groups of small polyps that step practically immobile and feed on microorganisms brought to them by water currents. Sea anemones, on the other hand, are solitary and can trap prey despite their limited locomotion.
- Worms are invertebrates with long, soft bodies and no legs.
- The body of most molluscs is soft, extremely flexible and without joints, yet has a large and very hard shell.
- Bivalves are sought after and cultivated for their pearls. Pearls are said to be the queen of gems, because they were discovered more than 4000 years ago and where used as important symbols in many ancient cultures.
Insects make up the largest and most varied group of arthropods. Most reproduce idli and their are insects adapted to any environment. Their bodies are protected by a form of armour. Arthur parts are currently believed to be the only living things capable of surviving a nuclear winter.
They have highly developed the sensory organs that enable them to see long distances. The diversity and sheer number of insect species estimated at 1.5 million for a testimony to their evolutionary success. They have been successful in part because they are a small, need less food than larger organisms and have developed the means of movement that keep them from being easy victims for predators.