Reproduction in Organisms

Reproduction


  • Reproduction is one of the fundamental characteristics of living organisms which could be defined as the formation of young ones by grown of individuals.
  • Juvenility, Maturity, Ageing and senescence and death are the 4 stages in life span where the site span cannot be correlated with size.
  • When offspring is produced by a single parent without gancetic fusion is which the offspring is only similar among themselves but are also exact copies of parent, the condition is noted as asexual reproduction.
  • Genetically similar individuals are called as clone.
  • Division of the parent body into 2 or more daughter individuals identical to parent is called fission.
  • If the parent organism divides into 2 halves it is termed as binary fission.
  • Simple irregular fission [Through any plane] Eg. Amoeba
  • Longitudinal fission [starts from flagella] Eg. Euglena.
  • Transverse type, eg: Paramecium, diatoms, Planaria and bacteria.
  • Oblique fission − dinoflagellates, ceratium
  • If the parent body divides into many similar daughter individuals, it is termed as multiple fission. Eg. Amoeba, plasmodium [is human]
  • Plasmotomy is a condition when multinucleated parent forms multinucleate daughter individuals without nuclear division. Eg. Giant amoeba [polonyna] and opaline [prolozone]
  • If the daughter individuals are formed from a bud/small part while arises from the parent body, the process is termed as budding -Eg. Yeast (Torulation)
  • In animals, budding can be (i) Exogenous (Hydra, Sycon, Tunicates) (ii) Endogenous (Spongilla)
  • The repeated formation of similar segments by budding is called as strobilation Eg. Taenia (neck)
  • Fragmentation is the mode where parent body breacking into 2 or more pieces which later develops as an individual.
  • Eg. Sponges, Sea anemones, starfish, spirogyra, Rhizopus, Riccia, marchantia, selaginella.
  • Sporulation is the mode of reproduction through spores which are minute, single celled, thick/thin walled propagules.
  • Zoospores are flagellated without cell wall [Eg. phycomycetes, Algae (Ulothrix, Chlamydomonas)]
  • Conidia [produced in conidiophores (Special hyphae branch)] Eg. Ascony cutes, penicillium
  • Oidiospores are formed under conditions of excess water, sugar and salts which multiply by budding. Eg. Agaricus
  • Chlamydospores are thick walled that stores resstue food, which could withstand long unfavourable conditions (Eg. Rhizopus, Agaricus)
  • Sporangiospore (Endospore) Eg. Rhizopus, mucor
  • Formation of new plants from Vegetative units (or) propagules is called vegetative propagation, by which a large number of population of clones is produced in shortest time.
  • Below in a list of propagation methods under natural method.
  • Roots (Tap/ Adventitious)
    Eg: Dalbergia, guava, Murraya, Sweet potato, Tapioca, Dahlia, Asparagus
  • Underground stem
    → Tubers - Eg. Artichoke, Potato
    → Bulbs - Eg. Garlic, Onion
    → Corms  - Eg. Colocasia, crocus
    → Rhizomes - Eg. Turmeric, Ginger, Adiantum, Banana
    → Suckes - Eg. Chrysanthemum, mint

  • Sub-accial stem (creepers)
    ⇒ Runnus (Cynodon/ centella/oxalis)
    ⇒ Stolon (Strawberry/ Vallisneria)
    ⇒ offset (one intermole long runners) ⇒ Eichhornia, pistia
  • Aerial stem : Eg. Sugar cone/opuntia (phylloclade)
  • Leaves Eg. Bryophyllum, Begonia, Adiantum
  • Bulbils (multilocular fleshy buds) Eg. Oxalis, Agave, Lily, Dioscorea (yam), Anan
  • Turions Eg. Potamogeton, Utricularia
  • Artifical methos of propagation is also called as Horticultural methods and the list of types are given below.
  • Cut pieces of below segments along with the root promoting chemicals such as IBA and NAA is given
  • Layering is rooting-cutting technique, where adventitious roots are induced to develop on stem (soft region) [one year old basal branch] and its pegged down in soil, which would develop roots called layer.
  • Types of layering - (i) Mound (Eg. Apple, pear, Guava) (ii) Air layering / Goote is the Commonest methods [Which involves the application of grafting clay]
  • Grafting clay: 2 parts of clay + 1 parts of hay/moss + , part Cow dung
  • Along with grafting clay, water is sprayed + IAA/ IBA/NAA is rolled along by a polythene bag - Eg. Litchi, Pomegranate, lemon, china Rose.
  • Grafting is a physical or physiological joining of separate individuals where root and shoot of 2 diff plants are broyh together to make a composite plant.
  • The method is not successful is monocotyledonous and which successful is comblum containing Eustelic plants.
  • Grafting involves 2 parts (i) Graft or jeion [A small shoot of superior character holding plant] and (ii) stock [a disease resistant food root system]
  • Both graft and stock are covered with grafting wase and bandage to form callus
  • Types of grafting: Tounge, wedges, Crown, side, Approach [inarching]
  • In approach grafting 2 independently growing plants are broyl together and later the seion is but below the graft and stock is cut above the graft.
  • Vegetative propagation is the only method of multiplication in selloum plants.
    Other advantages:
    ⇒ Repid multiplication
    ⇒ Genetic uniformity
    ⇒ Survival rate - 100%
    ⇒ disease free plants
  • Disadvantages:
    ⇒ no variation
    ⇒ Less adaptability
    ⇒ No dispersal
    ⇒ over crowding

Watch this video for the topic from 0:52 to 57:26

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