SS2 Second Term Biology Lesson Note – Reproductive Systems in Vertebrates

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WEEK 9                                                                                                                                                                                                                                                                                                          

CLASS: SS2

TOPIC: REPRODUCTIVE SYSTEMS IN VERTEBRATES

CONTENT:

(a) Reproductive systems in fish and reptile

(i) Structures of the male and female reproductive systems

(ii) Parts of the reproductive systems and their functions

(iii) Structures of the male and female gamete (sperm and ovum)

(iv) Differences between male and female reproductive organs.

SUB-TOPIC 1: STRUCTURES OF THE MALE AND FEMALE REPRODUCTIVE     SYSTEMS OF FISH AND REPTILE.

The reproductive system plays a vital role in the reproduction of organisms. Vertebrates like the fish and reptile have distinctive systems that are involved in the process of their reproductive reproduction.

FISH

In bony fishes like Tilapia, the male reproductive system is made up of two elongated testes that are surrounded from the abdomen. The testes join a simple duct which opens at a genital opening known as Cloaca. In the females, the ovaries are contained in sac-like structures also suspended from the abdomen. The ovaries are connected in a simple duct which leads to the genital opening.

Generalized Anatomy of a Fish

Both the digestive and circulatory systems in most fishes are rather simple. Although a few species can breathe atmospheric air, most fish breathe by means of gills. The swim (or gas) bladder allows fish to maintain a constant buoyancy regardless of the changing water pressure at varying depths.

In cartilaginous fish like shark the male reproductive system consists of the testes, vasa efferentia, vas deferens urino genital papilla, clasper and other inclusion that enhance reproduction. The testes are long cylindrical organs. The female reproductive system is made up of two ovaries.

Shark Egg Case with Embryos

These two dogfish egg cases show the developing embryos inside. Each egg case contains enough yolk to sustain the nutritional needs of the embryo until it hatches. The outer covering of the egg case is a tough, horny material. Each of the corners of the egg case is drawn out into a long coiled filament, or tendril, that wraps around rocks, kelps, or other materials on the sea floor, preventing the egg case from being carried away by currents and exposed to possible predation.

REPTILES

In reptiles e.g., lizard, the male has two testes located in the abdominal region. Tiny vessels emerge from the testes where sperm cells led to the epididymis. These vessels are known as vasa efferentia. Each epididymis opens into two protrusile penes.

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