SS2 Biology Lesson Note on Reproductive Systems in Vertebrates

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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.

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 protusitle penes.

In the female lizard the ovaries are found at the two sides of the abdomen. The oviducts open into the cloaca. During mating, the male penis penetrated through the female cloaca into the opening of the oviduct while the seminal fluid that contains sperm is released into the oviduct.

EVALUATION

1. What is reproduction?
2. Mention any parts of the reproductive system of a bony fish (male)
3. Mention any parts of the reproductive system of a reptile (female).

SUB-TOPIC 2: PARTS OF THE REPRODUCTIVE SYSTEMS AND THEIR FUNCTIONS

Some parts of the reproductive system of fish and their functions are as follows:

1. Testis – Production of sperms.
2. Ovary – production of ovaries
3. Seminal vesicle – storage of sperms
4. Cloaca – genital opening.

Some parts of the reproductive system of reptile and their functions are:

1. Ovoid testes: produces sperm cells.
2. Vas deferens: tiny vessels that carry sperms to the epididymis.
3. Ovaries: produce eggs.
4. Male penis: releases sperm into the oviduct

EVALUATION

1. What are functions of the following parts of a fish reproductive system:

1. Testes
2. Vasa efferentia
3. Seminal vesicle
4. Epididymus

2. In what way are the functions of the testes related to that of the ovary.

 

SUB-TOPIC 3: STRUCTURES OF THE MALE AND FEMALE GAMATES.

The male gamates of both fish and reptile are the sperm cells which are unicellular and mobile.

The female gametes on the other hand are the ova (ovum; singular) which are also unicellular but larger in size than the sperms, they are also called Eggs. They are produces by the ovary.

In reptiles the eggs have hair-like structures surrounding it which enable it to move into the oviduct.

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