HOW DO OGRANISMS REPRODUCE ? -Class-10

CONTENT LIST

HOW DO OGRANISMS REPRODUCE?

Reproduction

Reproduction is a biological process by which the development of new organisms from the existing organisms of the same species take place.

Reproduction means production of offsprings but It is not necessary for an organism to reproduce to stay alive.

It is fundamental feature of living organisms which ensure the continuity of species to maintain ecosystem.

If the organisms would not reproduce the species would extinct once they all are dead.

DO ORGANISMS CREATE EXACT COPIES OF THEMSELVES?

Yes, Reproduction in organisms create new individuals that look very much like themselves.

Reproduction at basic level will involve making copies of the blueprints of body design.

Chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA.

DNA of chromosomes in the nucleus of the cells has the information about protein creation. Which lead to body design of an organism.

DNA replicates inside the cell with support of various enzymes and this is accompanied by division of the cell.

Thus, fundamental process of reproduction is DNA replication.

The proteins are made in the new cell according to the prevexisting DNA codes. That's why the cell evolves as a new individual which looks similar to the original.

The Importance of Variation

The process of replication is not completely reliable and sometimes changes occur during the process of DNA replication. Thus, new DNA is created is different from the original one. This change in the information on DNA implies the initiation of variation.

In this way, with each generation, daughter cells are somewhat different from parent cells. Which leads to variation in the species , and the basis of evolution.

Cells divide and reproduce in two different way, mitosis and meiosis.

Mitosis cell division results in two identical daughter cells.

Modes of reprouction used by single organism

Asexual reproduction

Asexual reproduction take place without the involvement the fusion of male and female gametes.

In a Asexual type of reproduction , only a single organism gives rise to a new individual.

Offsprings devloped as a result of asexual reproduction are genetically identical to the parent in asexual reproduction.

This kind of reproduction is practised widely by unicellular organisms.

This process involves rapid population growth and no mate is required for the process.

Asexual reproduction is further divided into:

Binary Fission: When cell undergoes cell division and splits into two each cell carrying a copy of the DNA from the parent cell. For eg., amoeba.

Budding: In this process a small bud-like outgrowth gives rise to a new individual. The outgrowth remains attached to the parent organism until it is fully grown and then detaches itself and lives as an individual organism. For eg., hydra

Fragmentation: In this, the parent organism splits into several parts and each part grows into a new individual. For eg., Planaria

Sporogenesis: In this type of reproduction, a new organism grows from the spores. It can be created without fertilization and can spread through wind and animals.

Vegetative Propagation

Vegetative reproduction is a kind of asexual reproduction occurring in plants in which a new plant grows from a fragment or cutting of the parent plant .

Spore Formation

Spore Formation is a method in Asexual Reproduction in which Spores which are stored in sacs (called Sporangia). When Sporangia burst spores are obtained.

Sexual reproduction

Sexual reproduction involves the production of an offspring by the fusion of male and female gametes.

This process is known as fertilization.

Fertilization can be external or internal.

External fertilization is a process in which the male sperm fertilizes with female egg outside the female’s body.

In internal fertilization, the fusion of male and female gametes takes place inside the body of the female.

These gametes are formed either by the same individual or by different individuals of the opposite sex.

This process is slow and complex compared to asexual reproduction.

Why the Sexual Mode of Reproduction?

The sexual mode of reproduction is considered better than the asexual mode.

Sexual reproduction creates diversity in the genetic meterials of the offspring due to the combination of genes from two different individuals.This help them to adapt to different environments.

Genetic variation donot takes place in asexual reproduction since only one parent is involved.

Sexual Reproduction in Flowering Plants

All Flowering plant reproduces sexually through a process called pollination.

The flowers contain both male sex organs called stamens and female sex organs called pistils.

The anther is the part of the stamen which contains pollen. This pollen have to be move to a part of the pistil called the stigma for Pollination.

There are two ways of Pollination:

Self-pollination

Cross-pollination

Self-pollination occurs when a plant’s own pollen fertilizes its own ovules.

Cross-pollination occurs when the wind or animals move pollen from one plant to fertilize in the ovules on a different plant.

The advantage of cross-pollination is to create genetic diversity.

Some plants have special features that prevent self-pollination, such as pollen and ovules that develop at different times.

Reproduction in Human Beings

Puberty is the period during which adolescents reach sexual maturity and become mature and capable of reproduction.

Reproduction in human is by sexual reproduction process. where both the male and female gametes fertilize to give rise to an embryo.

The fertilization of human embryo takes place inside the body of the female, that's why is called Internal Fertilization.

Human is viviparous organism who give rise to Embryos directly rather of laying eggs.

In human, male reproductive system comprises of external organs. The testes in the scrotum produce the male gamete called sperm which is ejaculated in seminal fluid by the penis.

The female reproductive system comprises of internal organs. The female gamet called ovum is produced in the ovaries and is released monthly to travel to the uterus via the Fallopian. tubes.

Fertilization takes place when the penis is inserted through the vulva into the vagina and sperm is ejaculated towards the cervix. If an ovum is present in the uterus, it is then fertilized by sperm that manage to enter inside the cervix.

After fertilization ovum becomes a zygote and further develops into a fetus in the uterus.

an ovum becomes a zygote and develops into a fetus in the uterus.

Natural birth baby occurs after nine when the fetus is pushed from the vagina .

Male Reproductive System

The male reproductive system consists of a group of organs which make up a man’s reproductive and urinary system.

Function of organs are:

Male Reproductive System produce, maintain and transport the male reproductive cells called sperm and semen (the protective fluid around sperm) and discharges sperm into the female reproductive tract.
Produce and secrete male sex hormones.
The male reproductive system is made up of both kinds of organs internal and external parts. These organs help to urinate and sexual intercourse and make children.

Three main parts of Male Reproductive System

Penis — It is used for urination and sexual intercourse.
Scrotum — It is a loose bag of skin which hangs outside the bodyand located behind the penis.
Testes (or testicles) — It is a pair of egg-shaped glands that reside in the scrotum, on the outside of the body.

Female Reproductive System

Vagina: Vagina is a canal that joins the cervix (the lower part of uterus) to the outside of the body. It also is known called as the birth canal.

Uterus (womb): It is a hollow, pear-shaped organ which is the home to a developing fetus. It is divided into two parts: the cervix, which is the lower part that opens into the vagina, and the main body of the uterus, called the corpus, which can easily expand to hold a developing baby. A canal like passage through the cervix allows sperm to enter and menstrual blood to exit.

Ovaries: The ovaries are small and oval-shaped glands which is located on either side of the uterus. Prime function of ovaries is to produce eggs and hormones.

Fallopian tubes: These are narrow tubes which are attached to the upper part of the uterus and acts as pathways for the ova (egg cells) to travel from the ovaries to the uterus. Fertilization of an egg by a sperm occurs in the fallopian tubes. The fertilized egg further moves to the uterus, where fertilized egg implants to the uterine lining.

What happens when the Egg is not Fertilised?

If the egg is not fertilized it lives for about one day.Ovary releases one egg per month. At the same time, the uterus prepares itself and become ready to receive a fertilized egg. The endometrium lining of utreus becomes thick and spongy for carrying embryo. The endometrium lining of utreus provide nourish the embryo if had fertilization taken place. In absence of fertilization, this lining breaks and as a results of discharge of blood and mucous through vagina.

Reproductive Health

Reproductive Health refers complete physical, mental and social well-being in all aspects of reproduction. People should have enough knowledge on the following subject :

Knowledge of reproductive processes & organs
Care of mother & child
knowledge of various implecation related to sex

Many diseases can be sexually transmitted such as gonorrhoea and syphilis, and viral infections such as warts and HIV-AIDS.The risk of these disease can minimized by using a covering, called a condom, for the penis during sex.

The sexual act always has the possibilies of pregnancy. Pregnancy creates major demands on the body and the mind of the woman, and if she is not ready for it, her health will be adversely affected. Therefore, many ways have been devised to avoid pregnancy Contraception to avoid pregnancy can be achieved by the use of condoms, oral pills, copper-T and other methods.