Reproduction in Organisms
- 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.
⇒ Repid multiplication
⇒ Genetic uniformity
⇒ Survival rate - 100%
⇒ disease free plants
⇒ no variation
⇒ Less adaptability
⇒ No dispersal
⇒ over crowding
Watch this video for the topic from 0:52 to 57:26
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