Distinguish among the major groups of fish and explain how t

Distinguish among the major groups of fish and explain how they differ from one another

Describe the identifying characteristics of members of Class Chondrichthyes including the different ways they reproduce

Name characteristics that differentiate members of Class Chondrichthyes and Class Actinopterygi, and Sarcopterygii

Describe the main characteristics of the 2 subphyla of invertebrate chordates including when in each life cycle the chordate characteristics are seen

How do sharks maintain buoyancy? How do bony –fishes?

Solution

Answer:

(a) There are three major group of fishes which are Agnatha(jawless fishes), Chrondrichthyes(cartilaginous fish) and Osteichthyes(Bony fishes). This Osteichthyes group is subdivided into ray finned group and lobe finned group.

(b) Characteristics of Chrondrichthyes: The member of the Chrondrichthyes poses true bone and also poses a skeleton made up of cartilage. Only the teeth of this species and rarely the vertebrae are calcified. eg: Sharks

Reproduction in cartilaginous fishes is complex, and starts with copulation. The claspers are filled with sperm from the urogenital papilla of the male and inject the seminal fluid into the female. Fertilization is internal in the female: sperm is stored in the oviducts and fertilizes the eggs entering them from the ovaries. Cartilaginous fishes typically produce few, large, yolky eggs and have a low rate of reproduction. Young are born or hatched at an advanced stage of development after an extended gestation or incubation period that may extend from a month in some egglaying sharks to over two years in some livebearing sharks. There is no free-swimming larval stages in cartilaginous fishes, unlike many bony fishes, and newborn or newly hatched individuals usually resemble miniature adults. Some egg-laying sharks and skates have elongated tails when hatched, but these soon assume more adult proportions as the hatchling grows.

(c) Skeleton of Chondrichthyes are made of cartilage rather than bone whereas Actinopterygi and Sarcopterygii both have skeleton made of bone.

(d) Sharks maintain buoyancy through huge oily liver. In contrast, Bony fish achieve neutral buoyancy through an air filled sac called the swim bladder by varying the gas pressure inside the fish\'s body to allow it to sink or rise in the water.