REPRODUCTION THAT INVOLVES GENERATION OF A DNA COPY AND ADDITIONAL CELLULAR APPARATUS BY THE CELL INVOLVED IN THE PROCESS. DIFFERENT ORGANISMS USE VARIOUS MODES OF REPRODUCTION DEPENDING ON THEIR BODY DESIGN OR ORGANISATION.
ASEXUAL REPRODUCTION -
IS A TYPE OF REPRODUCTION WHICH DOES NOT INVOLVE FUSION OF GAMETES OR CHANGE IN THE NUMBER OF CHROMOSOMES THE OFFSPRING THAT ARISE BY ASEXUAL REPRODUCTION BY SINGLE CELL OR A MULTI-CELLULAR ORGANISM INHERIT GENE OF THAT PARENTS.
TYPE OF ASEXUAL REPRODUCTION -
1 ) FISSION-
FOR UNICELLULAR ORGANISMS, FISSION OR CELL DIVISION, RESULT IN THE CREATION OF NEW INDIVIDUALS. VARIOUS PATTERNS OF FISSION HAVE BEEN OBSERVED. MANY PROTOZOA AND BACTERIA SIMPLY SPLIT INTO TWO EQUAL HALVES DURING CELL DIVISION. IN ORGANISMS LIKE AMOEBA , THE SPLITTING OF THE TWO CELLS IN DIVISION CAN OCCUR IN ANY PLANE.
LEISHMANIA (WHICH CAUSE KALA-AZAR), WHICH CONTAIN A WHIP-LIKE STRUCTURE AT ONE END OF THE CELL IN THESE ORGANISMS, BINARY FISSION TAKES PLACE IN A DEFINITE ORIENTATION IN RELATION TO THESE STRUCTURES. OTHER UNICELLULAR ORGANISMS, LIKE THE MALARIAL PARASITE, PLASMODIUM, DIVIDE INTO MANY DAUGHTER CELLS BY MULTIPLE FISSION.
2) FRAGMENTATION -
IN MULTI-CELLULAR ORGANISMS HAVING RELATIVELY SIMPLE BODY DESIGN, SIMPLE REPRODUCTIVE METHODS CAN STILL WORK. FOR EXAMPLE, SPIROGYRA, SIMPLY SPLIT INTO SMALLER PIECES UPON MATURATION. THE FRAGMENTS OR PIECES GROW INTO NEW INDIVIDUALS. MANY MULTI- CELLULAR ORGANISMS ARE NOT SIMPLY A RANDOM COLLECTION OF CELLS SPECIALISED CELLS ARE ORGANISED AS TISSUES AND TISSUES ARE ORGANISED INTO ORGANS, WHICH THEN HAVE TO BE KEPT AT DEFINITE OR DIFFERENT POSITIONS IN THE BODY . CELL-BY CELL DIVISION WOULD BE IMPRACTICAL.
3) REGENERATION -
MANY FULLY DIFFERENTIATED ORGANISMS HAVE THE ABILITY TO PRODUCE NEW INDIVIDUAL ORGANISMS FROM THEIR OWN BODY PARTS. IF THE INDIVIDUAL IS SOMEHOW BROKEN UP OR CUT INTO DIFFERENT PIECES, MANY OF THESE PIECES GROW INTO SEPARATE INDIVIDUALS. FOR EXAMPLE, SIMPLE ANIMALS LIKE PLANARIA AND HYDRA CAN BE BROKEN INTO A NUMBER OF PIECES AND EACH PIECES GROWS INTO A COMPLETE ORGANISMS.THIS IS CALLED AS REGENERATION. REGENERATION AND PRODUCE A LARGE NUMBER OF CELLS. FROM THESE CELLS, DIFFERENT CELLS UNDERGO VARIATIONS TO BECOME VARIOUS CELL TYPE AND TISSUES. THESE CHANGES OCCUR AND IN AN ORGANISED SEQUENCE REFERRED TO AS DEVELOPMENT.
4) BUDDING -
ORGANISM LIKE HYDRA USE REGENERATIVE CELLS FOR REPRODUCTION IN BUDDING PROCESS. IN HYDRA, A BUD DEVELOPS AS AN OUTGROWTH BECAUSE REPEATED CELL DIVISION AT ONE SPECIFIC SITE. THESE BUDS DEVELOP INTO TINY INDIVIDUAL AND WHEN BECOME FULLY MATURE , DETACH FROM THE PARENT BODY AND PRODUCE NEW INDEPENDENT INDIVIDUAL.
5) VEGETATIVE PROPAGATION -
THESE ARE VARIOUS PLANT IN WHICH PARTS SUCH AS THE ROOTS, STEM AND LEAVES DEVELOP INTO NEW PLANT UNDER SOME SPECIFIC CONDITIONS. PLANTS , UNLIKE IS MOST ANIMALS, CAN INDEED USE SUCH A MODE OF REPRODUCTION. THIS PROPERTY OF VEGETATIVE PROPAGATION IS USED IN METHOD LIKE LAYERING OR GRAFTING TO PRODUCE MANY PLANT LIKE ROSES, SUGAR CANE OR GRAPES FOR AGRICULTURAL PURPOSES. PLANTS REPRODUCE BY VEGETATIVE PROPAGATION CAN BEAR FLOWER AND FRUITS COMPARATIVELY EARLIER THEN THOSE PRODUCED FROM SEEDS . SUCH METHOD ALSO MAKE THE PROPAGATION OF PLANT POSSIBLE SUCH AS BANANA , ORANGE , JASMINE AND ROSE THAT HAVE LOST THE CAPACITY TO PRODUCE SEEDS . ANOTHER ADVANTAGE OF VEGETATIVE PROPAGATION IS THAT ALL PLANTS RAISED ARE GENETICALLY SIMILAR ENOUGH TO THE PARENT PLANT TO CONTAIN ALL ITS CHARACTERISTICS .
6) SPORE FORMATION - EVEN IN VARIOUS SIMPLE MULTI-CELLULAR ORGANISM SPECIFIC REPRODUCTIVE ORGAN CAN BE IDENTIFIED . THE THREAD LIKE STRUCTURES THAT PRODUCED ON THE BREAD ARE THE HYPHAE OF THE BREAD MOULD (RHIZOPUS) . THEY ARE NOT REPRODUCTIVE PART . THE TINY BLOB-ON-A-STICK STRUCTURES ARE ALSO TAKE PART IN REPRODUCTION . THE BLOBS ARE SPORANGIA , WHICH HAVE CELLS OR SPORES , THAT CAN EVENTUALLY GROW AND DEVELOP INTO NEW RHIZOPUS INDIVIDUALS.
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