Fragmentation – Class 12 | Chapter – 1 | Short Notes Series PDF

Fragmentation: Fragmentation is one of the important mechanisms that take place in multicellular organisms. As the name suggests, it involves splitting organisms into different fragments. It is a form of asexual reproduction. Fragmentation type of reproduction can be defined as splitting of organisms into different fragments, each of these fragments is capable of developing into mature, and fully grown individuals that are identical to their ancestors.

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Fragmentation

Fragmentation

As discussed above, fragmentation is a process of splitting. Hence, it is also known as splitting. This method of reproduction is seen in many organisms such as filamentous cyanobacteria, lichens, many plants, and molds. It is also seen in animals such as sponges, acoel flatworms, sea stars, and some species of annelid worms.

Fragmentation in various organisms

Fragmentation in Diverse Organisms

  • Fragmentation in Fungi

Fragmentation is seen in various types of fungi such as molds, yeasts, mushrooms. They do reproduction by fragmentation utilizing a specific type of structure, known as hyphae. Hyphae can be defined as each of the branching filaments that make up the mycelium of a fungus. It is a branched portion of the parent fungi body and they can easily get rid off it. During the lifecycle of hyphae, they obtain food and other nutrients from the parent fungi body. By doing this, hyphae eventually grow and become mature, and ultimately, they become ready for fertilization. Now, a piece of hyphae breaks off from the parent body and enters into a growth phase as an individual body. Eventually, they also mature and grow hyphae, and this way, the cycle continues. 

  • Fragmentation in Lichens

Lichen is a composite organism resulting from algae or cyanobacteria that live in a mutualistic relationship between filaments of multiple species of fungi. The combined lichen has different properties than those of the organisms that make up it. Lichens come in a multitude of colors, sizes and shapes. Many lichens create specialized structures that can break and disperse easily. These structures include both mycobiont hyphae and algae(phycobiont) (see soredia and isidia). Larger thallus fragments may break up when the lichen dries or because of mechanical disturbances (see the lichens reproduction section).

Fragmentation in Plants

Fragmentation is a very common type of vegetative reproduction. Fragmentation is when a shoot that has been rooted becomes detached from the main group. There are many other mechanisms that plants use to fragment their cells. Natural fragmentation can also occur in other plants.

Specialised structures (Reproductive). Very few plants can form adventitious plants on their leaves. These plantlets would then detach and become individual plants. Some plants produce organs such as turions or bulbils.

Fragmentation can occur even in non-vascular plants. This is common with liverworts and mosses. The wind, animals, and water carry moss stems or leaves. When the moss fragment is in a suitable environment, it will root itself to become a new plant.

People use fragmentation to artificially propagate plants by cutting, layering and grafting. Many plants can be artificially propagated by fragmentation, including layering, cuttings and grafting.

Fragmentation in Animals

Natural fragmentation and reproduction occur in animals such as coral colonies and sponges. Different species of sponges and coral colonies can reproduce using this method.

This reproduction method is used by flatworms and annelid species. Animals such as sponges and colonies of corals fragment and reproduce naturally. This method reproduces many species of annelids and flatworms.

While certain developmental changes can cause splitting, terms like architomy and paratomy are widely used. Paratomy is the process whereby an animal splits into two pieces. Each piece would have its own tissues and organs. Architomy is where organisms are split into fragments that then become mature organisms.

Furrows may develop at the area of splitting before the animal splits. A fragment must not have a head to be able to regenerate a head.

Paratomy is a split where the anteroposterior is perpendicular to the anterior axis. This allows for the pre-generation of anterior structures in the posterior. As their body’s axis is properly aligned, both organisms will develop head to tail. Paratomy and budding are very similar, with the exception that their body’s axis is not correctly aligned.


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By Team Learning Mantras