Taxonomy (Biology) Part-I

Echinoderm is the common name given to any member of the Phylum Echinodermata of marine animals. The adults are recognizable by their (usually five-point) radial symmetry and include such well-known animals as starfish, sea urchins, sand dollars and sea cucumbers.

Most animals of phylum Echinodermata are oviparous and only some of them are viviparous. Oviparous animals lay eggs, with little or no other embryonic development within the mother.

Hydra has no blood but respires. In hydra both, the gaseous exchange and excretion occur by simple diffusion. Hydra are simple, aquatic animals belonging to the phylum Cnidaria.

They lack a circulatory system like blood and blood vessels, making them unable to transport gases and nutrients through a network of vessels.

Oxygen diffuses directly from the surrounding water across the hydra's thin body wall and into its cells, where it is used for respiration. Carbon dioxide, a waste product of respiration, also diffuses from the cells out of the body through the body wall.

Similar to respiration, nitrogenous wastes and other waste products are excreted from the hydra's body through the body wall via diffusion.

Crayfish, also known as crawfish, crawdads or mudbugs, are freshwater crustaceans resembling small lobsters to which they are related taxonomically. They are the members of the superfamilies Astacoidea.

Jellyfish is also known as Aurelia. They are classified as free-swimming marine animals consisting of a gelatinous umbrella-shaped bell.

Catfish (order Siluriformes) are a diverse group of ray-finned fish. Named for their prominent barbels which resemble a cat’s whiskers, catfish range in size and behavior.

The lightweight structure of the cartilaginous skeleton, combined with large, oil-rich livers, contributes to sharks' buoyancy, allowing them to float more easily. The flexibility of cartilage allows sharks to move through narrow spaces and make quick turns, crucial for hunting and maneuvering in the water.