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(a) Name The Mode of Reproduction of the Following Organisms and State the Important Feature of Each Mode: (i) Planaria (ii) Hydra (iii) Rhizopus (b) We Can Develop New Plants from The Leaves of Podophyllum. Comment. (c) List Two Advantages of Vegetative Propagation Over Other Modes of Reproduction.
(a) Mode of Reproduction in Planaria, Hydra, and Rhizopus
Planaria is a free-living flatworm that can regenerate its entire body from just a small fragment of its body. The mode of reproduction in planaria is asexual, which means it involves only one parent. This type of reproduction is known as regeneration. Planaria reproduces through fragmentation, where the body of the worm splits into two or more pieces, and each fragment grows into a new individual.
Planaria has the ability to regenerate any missing body part, including the head, tail, and even the brain. The important feature of asexual reproduction in planaria is that it can regenerate its entire body from a small fragment, and this ability has made it an important model organism in the study of regeneration and stem cell biology.
Hydra is a freshwater cnidarian that has a cylindrical body with tentacles around its mouth. Hydra reproduces asexually by a process known as budding. In this mode of reproduction, a small outgrowth called a bud develops on the body of the parent organism. The bud grows in size and eventually detaches from the parent to form a new individual.
The important feature of asexual reproduction in hydra is that it allows for the rapid production of offspring without the need for a mate. This mode of reproduction is advantageous in environments where the chances of finding a mate are low. Also, the offspring produced through budding are genetically identical to the parent, ensuring the preservation of desirable traits.
Rhizopus is a filamentous fungus that reproduces both sexually and asexually. The asexual mode of reproduction in Rhizopus is through the production of spores. The spores are produced at the tips of specialized structures called sporangiophores. The sporangiophores are long stalks that support a bulbous structure called the sporangium, which contains the spores.
The important feature of asexual reproduction in Rhizopus is that it allows for the production of a large number of spores that can disperse over long distances, increasing the chances of survival and colonization of new habitats. Spores can survive adverse environmental conditions such as drought, high temperatures, and low nutrient availability, ensuring the persistence of the species.
(b) Developing new Plants from the Leaves of Bryophyllum
Bryophyllum is a genus of succulent plants that belongs to the Crassulaceae family. Bryophyllum has the ability to produce new plants from the leaves, a process known as vegetative propagation. The leaves of Bryophyllum contain specialized structures called adventitious buds, which have the ability to develop into new plants under favourable conditions.
Vegetative propagation in Bryophyllum is advantageous as it allows for the rapid production of new plants without the need for seeds. This mode of reproduction is particularly useful in areas with harsh environmental conditions where the chances of seed germination are low. Also, vegetative propagation ensures the preservation of desirable traits as the new plants are genetically identical to the parent plant.
To propagate Bryophyllum, the leaves are cut from the parent plant and allowed to dry for a few hours to form a callus. The leaf is then placed on moist soil or sand, and after a few weeks, new plantlets emerge from the adventitious buds. The new plants can be transplanted to new pots or directly into the garden.
(c) Advantages of Vegetative Propagation Over Other Modes of Reproduction
Vegetative propagation has several advantages over other modes of reproduction such as sexual reproduction. Two of the main advantages are −
Preservation of Desirable Traits
Vegetative propagation ensures the preservation of desirable traits as the new plants are genetically identical to the parent plant. This is particularly useful in agriculture where farmers want to maintain desirable traits such as high yield, disease resistance, and quality characteristics in their crops. By using vegetative propagation, farmers can produce new plants that are genetically identical to the parent plant, ensuring the preservation of desirable traits.
Rapid Production of Offspring
Vegetative propagation allows for the rapid production of offspring without the need for seeds. This is particularly useful in environments where the chances of seed germination are low or where the growing conditions are harsh. By using vegetative propagation, farmers can produce new plants quickly and easily, ensuring a reliable supply of crops.
Another advantage of vegetative propagation is that it can be used to produce plants that are difficult to grow from seeds. For example, some plants such as bananas and grapes do not produce seeds or produce seeds that are difficult to germinate. By using vegetative propagation, farmers can produce new plants of these species easily and reliably.
In conclusion, the mode of reproduction in Planaria, Hydra, and Rhizopus differ significantly. Planaria reproduces asexually through fragmentation, Hydra reproduces asexually through budding, while Rhizopus reproduces asexually through the production of spores.
Podophyllum has the ability to produce new plants from the leaves through vegetative propagation, which is advantageous in preserving desirable traits and rapid production of offspring. Vegetative propagation is also useful in producing plants that are difficult to grow from seeds.
Overall, understanding the different modes of reproduction in organisms can provide insights into their biology and evolution, and can also have practical applications in agriculture and medicine.
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