Chapter 1

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Reproduction-

  1. The Period between birth and natural death off in an organisms is called it's life Spain .it can very from less than a day to more than 400 yrs .Whatever be the lifespan death of every individual organism is a certainly . i.e. No individual is immortal , except single celled organisms.

Life Spain of some organism are given in the following table.

2. Reproduction is a biological process of continuity of a race in which the grow up individual give rise to offspring similar to them .

It perform the following function.

  • Enable continuity off species .

  • Maintain life on the earth.

  • Create variation among population.

the mechanism to produce offspring show large variation depending on organism habitat its internal physiology and several other factors.

Based on the participation of one or two organisms.Reproduction is can be following of two type-

  • Asexual reproduction

  • Sexual reproduction

(1) Asexual reproduction-A single parent is capable of producing offspring thus the office spring are genetically and morphologically identical to one another and to there parents. These are often referred to as a clone. The unit of the Reproduction is commonly formal from a somatic cells of the parents. Meiosis does not occur in Asexual reproduction.

Asexual reproduction is common among single celled organisms and in plant and animal with simple organization. Cell division in itself is a mode of reproduction in protists bacteria and monerans . e.g. Amoeba ( the parent cell divide into two to give rise to new individuals).

Types of asexual reproduction are as given below.

I) fission can be further classified as-

(1) Binary fission-the body of an individual divided into two equal halves.

It can be following type.

(a) Simple binary fission -when division in An occurs in any planes but it is always right angle to the elongated dividing nucleus example- amoeba.

(b) Longitudinal binary fission- fission when division occurs along the longitudinal access for example - Euglena , Vorticella.

(c) Oblique binary fission-when division occurs at an angle to the transverse axis. example - Ceratium .

(d) Transverse binary fission - when division occurs along the transverse axis of the individual. example - paramecium.

(2). Multiple fission -the division of parent body into many daughter organism example amoeba, plasmodium, Monocytes

II) Budding (torulation) - An outgrowth or bud develop grow constricts at the base at the separate of parent body. Example yeast,and Hydra. The complex budded condition is called torala stage.

III) Sporulation - It occurs by tiny single celled thin walled spores that are extremely resistant to environmental extremes . The spore form new individual.it commenly occurs in monera , protista,fungi algae.

Spore can be of following main type-

  • Pseudopodio spore Amoeba.

  • Zoospore Chamydomonas.

  • Conidia Penicillium

  • Sporangiospore Rhizopus

  • Gemmules Sponges

IV) Fragmentation - occurs by breaking off the parents body into two or more part each of which grow to form an independent individual for example - spirogyra and bryophytes such as Marchantia ,Riccia

V) Regeneration- is a type of asexual reproduction in Witch missing part off an organism is repaired by proliferation of cells for example - hydra ,planaria and sponge .

VI) Vegetative propagation - is the formation of new plant from vegetative part like root, stem,leaf ,naturally water Hyacinth( scourage of water bodies of Terror of Bengal ) propagates very quickly by Vegetative mode and drains out dissolve oxygen (O2) of water bodies .some artificial method of vegetative propegation are also develop by the farmers like cutting , layering, grafting etc.

some examples of natural method of Vegetative propegation-.

Vegetative part. Example

•Root. Dahelia , asparagus ,guava,tapioca

Stems

• tubers Potato and Artichoke

•bulb. Garlic , onion

•Rhizome. Ginger, Turmeric ,Banana ,Dryopteris. •corm Colocasia ,Crocus, Amorphophallus • Suckers Mint and chrysanthemum. •Runner. Oxalis and centella • stolon. Jasmine. • offsets. Pistia and Eichhornia

• Leaves. Bryophyllum bagonia and walking fern

•Bulbils Agave Lily Dioscoreo •Tureons potomagoton and utriculeria .

The unit of vegetative propagation such as Runners , Rhizome sucker ,tuber, offsets,bulb all have capabilities to give rise to new offspring these structure are known as vegetative propagation.



We hope the given CBSE/MPBoard Class 12th Biology Chapter 1 "Reproduction In organisms" will help you.

Written By - Priyanka Sharma