Reproductive System

Asexual mode of reproduction

Let US study modes of reproduction involving a single parent, without involving gametes. These are known as asexual modes of reproduction.

Organisms Can reproduce asexually in many ways. Some of them are given here.

Fission

Single celled organisms, such as Paramecium and bacteria, reproduce by splitting into two or more offspring’s. This usually occurs in a symmetrical manner. They split into two by binary fission. When more cells are formed it is called multiple fission. This is often the only mode of reproduction in these organisms.

Budding

A growth on the body as a bud that grows to form nearly identical copy of parent. When the bud totally grows then it separates from the parent and survives independently. Ex: Yeast.

Fragmentation

Some can grow from a separate of parent organism. This can from any part of the body. This happens only in the simplest, such as some flatworms, moulds, lichens; Spirogyra etc. grow in this manner. These may also Produce sexually. Fragmentation is a common mode of Production in algae, fungi and many land plants.

Regeneration:

Many organisms have the ability to give rise to new individual organisms from their body parts. That is, if the individual is somehow cut or broken up into many pieces, these pieces grow into separate individuals. This is similar to fragmentation.

Male reproductive system:

In human males, the two testes are located in pocket like structure outside the body wall called the scrotum. The male reproductive cells, sperms, are produced in very large numbers (hundreds of millions).  male reproductive system and find out parts essential for the transport of the sperm cells. Each testis has several lobules and each lobule tin several somniferous tubules. They are small, highly coiled tubes and 80cm in length. Vasa efferentia collect spermatozoa from the tubules.

 Vasa efferentia forms epididymis. Here sperms are stored temporarily and moved into One prostate, two cowper glands which are accessory glands in male reproductive system secretes a fluid called semen. This provide nutrients for sperm to keep alive and helps as a medium for the movement of sperms

The sperm cell has a long tail. This helps them to move towards The ovum. The development of the male reproductive organs is regulated by the male sex hormone called testosterone know that secondary sexual characters are also controlled

By the male sex hormones, which are secreted by the testes.  The Production of sperms by the testes will begin when these events occur.

Men produce sperm, from the age of about 13 or 14 years, and can go on doing so most of their lives, although their power to do so decreases as they grow older.

Female reproductive system:

The two ovaries, where ova are formed, are located deep in the abdomen Of fema1e’s body .

The ova develop in tiny cellular structures called follicles, which at first look like cellular bubbles in the ovary. They are called graffian follicles. As a follicle grows, it develops a cavity filled with fluid. Each follicle contains a single ovum which is formed after the process of cell division (meiosis). When an ovum is mature, the follicle ruptures at the surface of the ovary and the tiny ovum is flushed out. This release of the egg or ovum is called ovulation.

Generally the ovum enters the widened funnel of an oviduct (fallopian tube), a tube that extends from the neighborhood of an ovary to the muscular, thick-walled uterus. Fertilization occurs as the ovum passes through the oviduct thus begins a new life, fertilization with sperm would lead to formation of a mass that might grow to form a baby.

Stage	Description
1.Prophase	1.Chromosomes contract, spiral and become visible even in light microscope and nucleoli become smaller (material to chromosomes) 2. Chromosomes split lengthwise to form chromatids, connected by centromeres. 3. Nuclear membrane disappears. 4. Centrosome, containing rod-like centrioles, divide and form ends of spindle (probably animal cells only). (Note: No pairing of chromosomes as in meiosis).
2. Metaphase	1. Chromosomes move to spindle equator, centromeres attached to spindle fibres. 2. Centromeres split, separating the chromatids.
3.Anaphase	1. Spindle fibres attached to centromeres contract, pulling chromatids towards poles
4.Telophase	1. Chromatids elongate, become invisible, (replication at this stage to become chromosomes). 2. Nuclear membranes form round daughter nuclei. 3. Cell membrane pinches in to form daughter cells (animals) or new cell wall material becomes laid down across spindle equator (plant& 4. Nucleus divides into two and division of cytoplasm starts.

Process of meiosis

Unlike mitosis which is a continuous process for division in most cells. Meiosis occurs only during the formation of gametes in sexual reproduction. Meiosis has two phases. During the first phase of meiosis the parent cell (containing two sets of chromosomes) divides twice, though the chromosomes divide only once. The second phase of meiosis is similar to normal mitosis, but chromosomes do not duplicate.

·         Reproduction is necessary for perpetuation and continuation of life.

·         Reproduction is of two types keeping in view of fusion of gametes- Sexual and Asexual.

·         In sexual reproduction only half of each parent’s chromosomes are passed to the next generation.

·         Fission, budding, fragmentation, regeneration, spore formation we the ways of asexual reproduction.

·         Several plants may be grown from vegetative parts like stems, roots, leaves etc and is called vegetative propagation.

·         Vegetative propagation may be natural or manmade. ft has got some economic 1mpotane

·         In grafting we can acquire desirable characters of plants

·         Tissue culture is a modern technique of growing plants ft helps to grow more plants in less time and place.

·         Sexual reproduction in higher animals is through specialised organs, distinctively male and female reproductive systems.

·         Cells divide for growth of the individual to repair and replace the worn out cells and also for the formation of gametes.

·         Cell division is of two types-a) Mitosis-or somatic cell division B) meiosis cell division.

·         The cell of the body may either be somatic cells that constitute the general body of the organism or germ cells that take part in formation of gametes.

·         G-1, G-2, S and M are the stages in a cell cyclic which ins manner

·         The longest phase is the synthesis phase in cell ck what duplication of genetic material takes place

·         At the end of mitosis two daughter cells are formed with the number of chromosomes same as that

 of their parents, It runs through Prophase, Anaphase Metaphase and Telophase.

·         Division of cytoplasm is called Cytokinesis.

·         During meiosis the parent cell divides twice and four daughter cells are formed.

·         Reproductive health is important to possess sound mind in a sound body.

·         One should be aware of the facts related to transmission of sexually transmitted diseases.

·         There is no cure for AIDS. Prevention is the only way to avoid it.

·         Now a days various methods of contraception are available to control child birth.

·         It is our responsibility to build a healthy society.

·        Determination of sex before birth is illegal.