Reproduction In Organisms

Asexual reproduction is the process by which genetically identical offsprings are produced from a single parent without gametes formation.

Plasmodium reproduces by multiple fission where a single parent cell divides into several small, equal sized daughter individuals.

Reproduction is essential to continue the species forever generations after generations. It is essential for the survival of a species.

Hydra is a multicellular organism which reproduces by budding process where an outgrowth called bud appears from parent’s body which grows into a new individual and gets separated from parent body.

Hydra is a simple multicellular animal which have tentacles and lives in freshwater which reproduces by budding method, an asexual method of reproduction.

Mucor reproduces asexually by spore formation. Spores are usually produced in sporangia. The fungal hypha develops an enlarged sporangium where spores are produced.

In spirogyra, filament breaks into small parts and each part grows into a new spirogyra.

In spirogyra, filament breaks into small parts and each part grows into a new spirogyra. This process is called fragmentation an asexual method of reproduction.

The cut part of plant stem which have roots fixed into soil in which grafting is performed is called stock.

Clones are the genetically identical individuals of an organism having same body features and are produced through asexual reproduction either naturally or artificially.

A. Two animals which reproduce sexually are human beings, lion.

They both produce male and female gametes, two parents are involved, male and female gametes unite to form zygote which grows into a full-term baby inside female’s body.

B. Two animals which reproduce asexually are hydra and amoeba.

Only one parent is involved without formation of gametes. Identical offspring’s are produced in case of asexual reproduction.

Paramecium reproduces by binary fission which is an asexual method of reproduction. The parent cell divides into two small nearly equal sized identical daughter cells which grow into adult organisms.

Yeast reproduces by budding asexually. A small outgrowth called bud arises from parent yeast cell during favourable conditions. It gradually enlarge, nucleus enlarges and divides into two. One of the nuclei goes to the bud. Bud grows and become larger equal in size to parent cell. It may separate out from parent cell or form chain of buds.

In hydra asexual method of reproduction is budding where an outgrowth called bud appears from parent’s body which grows into a new individual and gets separated from parent body.

In Plasmodium asexual method of reproduction is multiple fission where a single parent cell divides into several small, equal sized daughter individuals.

Cutting method is used in case of rose plant for reproduction where a small cutting of stem containing buds is planted on wet soil which will develops roots after few days and grows into a new plant. It is an artificial method of propagation.

Layering method is employed for production of citrus plants like lemon. In this method a part of stem is pulled towards ground and covered with soil, from which roots will develop after few days and it will grow into a new plant by detaching from parent plant.

Layering is defined as the process in which a part of stem is pulled towards the ground and covered with soil. This leads to growth of roots from the covered part and at that time it is removed from the parent plant and grows independently. Two plants which propagated by layering method are chrysanthemum and lemon.

Cutting of parts of plant such as stem, shoot or leaf which bore some buds are taken and lower part is buried in moist thus resulting in growth of roots and some days a whole plant. Two plants which propagated by cutting method are rose, bougainvillea.

Different methods of asexual method of reproduction are fission, budding, fragmentation, regeneration, spore formation, vegetative propagation etc.

a.

b. Amoeba reproduces by asexual method i.e. by binary fission.

Cats, human beings, birds reproduce sexually.

Regeneration is the ability of an organism to regenerate its lost parts of the body. Hydra and Planaria can regenerate fully from their cut body parts.

Regeneration is the process by which an organism has an ability to regenerate its lost parts of the body which might have been removed by injury or by some other methods. When Planaria or hydra is cut into many pieces, each piece grows into a complete organism. Regeneration is carried out by specialized cells which have the capacity to develop, proliferate and differentiate into various cell types and tissues.

The growth of new plants from vegetative parts of the plant like roots, stem, leaves other than the seeds is called vegetative propagation.

a. Cutting: Small piece of plant part like roots, stem or leaves is cut and is used for propagation. Examples: Rose, china-rose, sugarcane etc.

b. Layering: It is the process where roots are induced when a stem comes in contact with the ground. In this method a part of stem is pulled towards ground and covered with soil, from which roots will develop after few days and it will grow into a new plant by detaching from parent plant.

Examples: Grapevine, jasmine, litchi, mango, lemon etc.

Two advantages of vegetative propagation are-

a. It is cheaper, easier and rapid method.

b. The plants which cannot produce seeds also can be easily propagated by this method.

c. The plants produced by this method bear fruits and flowers earlier.

d. It produces new individuals with exactly identical qualities as the parent, which preserves the parental characteristics.

It is the process where roots are induced when a stem comes in contact with the ground. In this method a part of stem is pulled towards ground and covered with soil, from which roots will develop after few days and it will grow into a new plant by detaching from parent plant. Examples- lemon, chrysanthemum.

a. Tubers are thickened, enlarged modified stems which are found underground and are used as storage organs of nutrients. They serve as a food reserve for plants. Example- potato, yam.

b. Potato is propagated by using tubers. Buds present in the tuber of potatoes can grow into a new plant.

The growth of new plants from vegetative parts of the plant like roots, stem, leaves other than the seeds is called vegetative propagation.

There are various methods like cutting, layering, grafting which are artificial methods of vegetative propagation etc. Natural methods include modified tuberous roots, stems, buds on leaves etc.

In Bryophyllum adventitious buds develop from the notches of leaves when they fall down into moist soil and on getting proper conditions for growth, new plants arises from them. This is one example of natural method of vegetative propagation.

Amoeba reproduces by fission and spirogyra by fragmentation.

i. Fission: It is the process in which a unicellular organism splits into two or more daughter cells. They are mainly of two types- Binary fission which is seen in Amoeba, Paramecium and Multiple fission seen in Plasmodium.

The process by which there is division of a parent cell into several daughter cells is called multiple fission. During this process the nucleus of parent cell divides into many daughter nuclei along with the division of cytoplasm.

Binary fission

The genetic material first duplicates through mitosis leading to duplication of nucleus through karyokinesis and a constriction appears in the cell membrane which deepens and finally a single parent cell divides into two daughter cells. The division of cytoplasm is called cytokinesis. This mode of asexual reproduction is called binary fission.

ii. Fragmentation- In this case organism after maturation breaks into smaller fragments and each fragment grows into a new individual. This process is called fragmentation.

The process by which there is division of a parent cell into several daughter cells is called multiple fission. During this process the nucleus of parent cell divides into many daughter nuclei along with the division of cytoplasm.

Multiple fission seen in Plasmodium.

Fungi reproduce asexually by budding or spore formation.

Fungi like yeast reproduce by budding whereas mucor reproduce by spore formation.

Yeast reproduces by budding asexually. A small outgrowth called bud arises from parent yeast cell during favourable conditions. It gradually enlarge, nucleus enlarges and divides into two. One of the nuclei goes to the bud. Bud grows and become larger equal in size to parent cell. It may separate out from parent cell or form chain of buds.

Spores are reproductive parts and Hyphae are non-reproductive parts of Rhizopus.

Rhizopus reproduces through asexual method by spore formation. Spores are produced in sporangia. On maturation the walls of sporangia ruptures and spores are liberated out. They are covered with a thick wall which protects them from adverse conditions. On suitable conditions spores germinate and grow into new hyphae. The hyphae develop an enlarged sporangium. Nucleus within the sporangium divides several times and each nucleus gets surrounded by cytoplasm to form spore which gets matured inside sporangium.