Class 10 - Science
Chapter 8 - How Do Organisms Reproduce
INTRODUCTION
The production of new organisms from the existing organisms of the same species is known as Reproduction.
Reproduction is essential for the survival of a species on this earth.
The process of reproduction ensures the continuity of life on earth
TYPES OF REPRODUCTION
There are two main methods of reproduction in living organisms:
The production of new organisms from the existing organisms of the same species is known as Reproduction.
Reproduction is essential for the survival of a species on this earth.
The process of reproduction ensures the continuity of life on earth
TYPES OF REPRODUCTION
There are two main methods of reproduction in living organisms:
- Sexual reproduction
- Asexual reproduction
![Picture](/uploads/1/2/0/8/120834358/p2.jpg?250)
ASEXUAL REPRODUCTION
The production of a new organism from a single parent without the involvement of sex cells (or gametes) is called asexual reproduction.
For example: binary fission in amoeba, budding in hydra, spore formation in Rhizopus fungus, regeneration in Planaria, fermentation in spirogyra, etc.
The production of a new organism from a single parent without the involvement of sex cells (or gametes) is called asexual reproduction.
For example: binary fission in amoeba, budding in hydra, spore formation in Rhizopus fungus, regeneration in Planaria, fermentation in spirogyra, etc.
![Picture](/uploads/1/2/0/8/120834358/p3_orig.jpg)
SEXUAL REPRODUCTION
The production of a new organism from two parents by making use of their sex cells (or gametes) is called asexual reproduction.
For example: the humans, fish, frogs, hens, cats, dogs, etc.
The production of a new organism from two parents by making use of their sex cells (or gametes) is called asexual reproduction.
For example: the humans, fish, frogs, hens, cats, dogs, etc.
![Picture](/uploads/1/2/0/8/120834358/editor/p5.jpg?1533980412)
MODES OF ASEXUAL REPRODUCTION
1. FISSION
In the process of fission, a unicellular organism splits to form more organisms.
Types of fission:
1. FISSION
In the process of fission, a unicellular organism splits to form more organisms.
Types of fission:
- Binary fission
- Multiple fission
![Picture](/uploads/1/2/0/8/120834358/p7_orig.jpg)
2. FRAGMENTATION
The breaking up the body of a simple multicellular organism into two or more pieces on maturing, each of which subsequently grows to form a complete new organism is called fragmentation.
The breaking up the body of a simple multicellular organism into two or more pieces on maturing, each of which subsequently grows to form a complete new organism is called fragmentation.
![Picture](/uploads/1/2/0/8/120834358/p8_orig.jpg)
3. REGENERATION
The process of getting back a full organism from its body part is called regeneration.
The process of getting back a full organism from its body part is called regeneration.
4. BUDDING
In budding, a small part of the body of the parent organism grows out as a ‘bud’ which then detaches and becomes a new organism.
In budding, a small part of the body of the parent organism grows out as a ‘bud’ which then detaches and becomes a new organism.
5. VEGETATIVE PROPAGATION
In vegetative propagation, new plants are obtained from the parts of old plants like stems, leaves, etc., without the help of any reproductive organisms.
In vegetative propagation, new plants are obtained from the parts of old plants like stems, leaves, etc., without the help of any reproductive organisms.
![Picture](/uploads/1/2/0/8/120834358/745266703.gif)
6. SPORE FORMATION
In spore formation, the parent plant produces hundreds of microscopic reproductive units called ‘spores’. When the spore case of the plant bursts, then the spores spread into air. When these air- borne spores land on food under favorable conditions, they germinate and produce new plants.
ARTIFICIAL PROPOGATION OF PLANTS
The process of growing many plants from one plant by man- made methods is called artificial propagation.
TISSUE CULTURE
The production of new plants from a small piece of plant tissue or cells removed from the growing tips of a plant in a suitable growth medium is called tissue culture.
Fig. tissue culture technique of producing new plants
BENEFITS OF TISSUE CULTURE
*Time taken to obtain mature crop is very less.
*Crops are almost pest and disease resistant.
*Tissue culture techniques are cost effective.
MODES OF SEXUAL REPRODUCTION
Cross Pollination: The transfer of pollen from the male reproductive organ of one plant to the female reproductive organ of another plant. Insects and wind are the main agents of cross-pollination.
STRUCTURE OF FLOWER
The main parts of flower are:
Receptacle: The base of a flower to which all the parts of a flower are attached is called receptacle.
Sepals: Sepals are green outermost leaf-like floral organs which protect the flower in the bud stage.
Petals: The colorful parts of a flower are called petals.
Stamen: Stamen is the male reproductive part and it produces pollen grains that are yellowish in color.
Carpel: Carpel is present in the Centre of a flower and is the female reproductive part. It is also known as Pistil.
Stamen: The little stalks with swollen tops just inside the ring of petals in a flower are called stamens.
TYPES OF FLOWER
GERMINATION OF SEEDS
Beginning of the growth of seeds is called germination of seeds.
In spore formation, the parent plant produces hundreds of microscopic reproductive units called ‘spores’. When the spore case of the plant bursts, then the spores spread into air. When these air- borne spores land on food under favorable conditions, they germinate and produce new plants.
ARTIFICIAL PROPOGATION OF PLANTS
The process of growing many plants from one plant by man- made methods is called artificial propagation.
- Cutting: A small part of a plant which is removed by making a cut with a sharp knife is called a ‘cutting’.
- Layering: a method of propagating a plant in which a shoot is fastened down to form roots while still attached to the parent plant.
- Grafting: it is a method in which the cut stems of two different plants are joined together in such a way that the two stems join and grow as a single plant.
TISSUE CULTURE
The production of new plants from a small piece of plant tissue or cells removed from the growing tips of a plant in a suitable growth medium is called tissue culture.
Fig. tissue culture technique of producing new plants
BENEFITS OF TISSUE CULTURE
*Time taken to obtain mature crop is very less.
*Crops are almost pest and disease resistant.
*Tissue culture techniques are cost effective.
MODES OF SEXUAL REPRODUCTION
- SEXUAL REPRODUCTION IN PLANTS
- The plants in which the sex organs are carried within the flowers and the seeds are enclosed in a fruit are called angiosperms (flowering plants).
- The flowering plants are reproduced by sexual reproduction method.
- The function of a flower is to make male and female gametes and to ensure that fertilization will take place to make new seeds for the reproduction of plant.
- : The transfer of pollen grains from the anther of a stamen to the stigma of a carpel is called pollination.
- The pollination of a flower by pollen from the same flower or from another flower on the same plant.
Cross Pollination: The transfer of pollen from the male reproductive organ of one plant to the female reproductive organ of another plant. Insects and wind are the main agents of cross-pollination.
- Fertilization occurs when the male gamete present in pollen grain joins with the female gametes present in ovule.
STRUCTURE OF FLOWER
The main parts of flower are:
Receptacle: The base of a flower to which all the parts of a flower are attached is called receptacle.
Sepals: Sepals are green outermost leaf-like floral organs which protect the flower in the bud stage.
Petals: The colorful parts of a flower are called petals.
Stamen: Stamen is the male reproductive part and it produces pollen grains that are yellowish in color.
Carpel: Carpel is present in the Centre of a flower and is the female reproductive part. It is also known as Pistil.
Stamen: The little stalks with swollen tops just inside the ring of petals in a flower are called stamens.
TYPES OF FLOWER
- UNISEXUAL
- BISEXUAL
GERMINATION OF SEEDS
Beginning of the growth of seeds is called germination of seeds.
![Picture](/uploads/1/2/0/8/120834358/547630867_orig.jpg)
SEXUAL REPRODUCTION IN ANIMALS
The cells involved in sexual reproduction are called gamete.
The male gamete in animals is called sperm.
The female gamete in animals is called ovum or egg.
The cell which is formed by the fusion of a male gamete and female gamete is called zygote.
HUMAN REPRODUCTIVE SYSTEM
The reproductive system in human beings become functional at a definite age called puberty.
The age at which the sex hormones begin to be produced and the boy and girl become sexually mature is called puberty.
The various changes which occur in boys at puberty:
MALE REPRODUCTIVE SYSTEM
The purpose of the organs of the male reproductive system is to perform the following functions:
Penis:
Testicles (testes):
Seminal vesicles:
- An animal having male sex cells called sperms in its body is called male.
- An animal having female sex cells called ova in its body is called female.
The cells involved in sexual reproduction are called gamete.
The male gamete in animals is called sperm.
The female gamete in animals is called ovum or egg.
The cell which is formed by the fusion of a male gamete and female gamete is called zygote.
- The fusion of a male gamete with a female gamete to form a zygote during the sexual reproduction is called fertilization.
HUMAN REPRODUCTIVE SYSTEM
The reproductive system in human beings become functional at a definite age called puberty.
The age at which the sex hormones begin to be produced and the boy and girl become sexually mature is called puberty.
The various changes which occur in boys at puberty:
- voice gets lower or deeper.
- voice gets lower or deeper.
- Hair may grow on face, chest, and back.
- chest and shoulders get broader.
- hips get wider and your body may become curvier.
- breasts develop and get bigger.
- start getting your period.
- labia may change color and grow bigger.
MALE REPRODUCTIVE SYSTEM
The purpose of the organs of the male reproductive system is to perform the following functions:
- To produce, maintain, and transport sperm (the male reproductive cells) and protective fluid (semen).
- To discharge sperm within the female reproductive tract during sex.
- To produce and secrete male sex hormones responsible for maintaining the male reproductive system.
Penis:
- This is the male organ used in sexual intercourse.
- It has three parts: the root, the body or shaft; and the glans.
- The glans, also called the head of the penis.
- The body of the penis is cylindrical in shape and consists of three circular shaped chambers.
- This is the loose pouch-like sac of skin that hangs behind and below the penis.
- It contains the testicles (also called testes), as well as many nerves and blood vessels.
- The scrotum acts as a "climate control system" for the testes.
Testicles (testes):
- These are oval organs about the size of large olives that lie in the scrotum, secured at either end by a structure called the spermatic cord.
- Most men have two testes.
- The testes are responsible for making testosterone, the primary male sex hormone, and for generating sperm.
- The epididymis is a long, coiled tube that rests on the backside of each testicle.
- It transports and stores sperm cells that are produced in the testes.
- The vas deferens is a long, muscular tube that travels from the epididymis into the pelvic cavity.
- The vas deferens transports mature sperm to the urethra, the tube that carries urine or sperm to outside of the body.
- These are formed by the fusion of the vas deferens and the seminal vesicles.
- The ejaculatory ducts empty into the urethra.
- The urethra is the tube that carries urine from the bladder to outside of the body.
- In males, it has the additional function of ejaculating semen when the man reaches orgasm.
Seminal vesicles:
- The seminal vesicles are sac-like pouches that attach to the vas deferens near the base of the bladder.
- The seminal vesicles produce a sugar-rich fluid (fructose) that provides sperm with a source of energy to help them move.
- The prostate gland is a walnut-sized structure that is located below the urinary bladder in front of the rectum.
- The prostate gland contributes additional fluid to the ejaculate.
- These are also called Cowper's glands.
- These are pea-sized structures located on the sides of the urethra just below the prostate gland.
- These glands produce a clear, slippery fluid that empties directly into the urethra.
![Picture](/uploads/1/2/0/8/120834358/865893833_orig.jpg)
FEMALE REPRODUCTIVE SYSTEM
The female reproductive system is designed to carry out several functions:
The internal reproductive organs in the female include:
Vagina:
Fertilization of the ovum takes place in the oviduct.
REPRODUCTIVE HEALTH
The female reproductive system is designed to carry out several functions:
- It produces the female egg cells necessary for reproduction, called the ova or oocytes.
- The system is designed to transport the ova to the site of fertilization.
The internal reproductive organs in the female include:
Vagina:
- The vagina is a canal that joins the cervix (the lower part of uterus) to the outside of the body. It also is known as the birth canal.
- The uterus is a hollow, pear-shaped organ.
- The uterus 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.
- The ovaries are small, oval-shaped glands that are located on either side of the uterus.
- The ovaries produce eggs and hormones.
- These are narrow tubes that are attached to the upper part of the uterus.
- the fertilization of an egg by a sperm, normally occurs in the fallopian tubes.
Fertilization of the ovum takes place in the oviduct.
REPRODUCTIVE HEALTH
- Reproductive organs need a lot of care and hygiene, otherwise they are susceptible to many infections or diseases.
- The diseases which spread through sexual routes are known as sexually transmitted diseases e.g., bacterial infections like syphilis, gonorrhea and viral infections such as warts and HIV- AIDS.
- Condom helps to prevent transmission of many of these infections to some extent.
- Many ways have been devised to avoid pregnancy. Contraception can be achieved by:
- • Mechanical barrier method (use of condoms).
- • Chemical methods (use of pills).
• Use of contraceptive devices (copper-T).
• Surgical methods (vasectomy in males and tubectomy in females)