If you look at the body of a higher seed plant and any kind of algae, you will notice a big difference in structure and morphology. And this is not surprising, because it has evolved so that modern flowering plants are much higher organized than real algae. The main difference is the body structure, which in algae and some other organisms is presented in the form of a thallus.
What is a thallus?
The shape of most modern algae is very diverse, due to the simple structure of the body, which during evolution changed and transformed, depending on the environment and other important natural factors. The body of the body, which is not divided into separate functionally independent organs and consists of poorly specialized tissues, is a thallus. This definition is suitable not only for algae, but also for many mosses, as well as all lichens and some mushrooms.
Thallus is an important sign of the simplest development of plants and other organisms. It performs all the functions at once, which would belong to the leaves, root or stem separately with a more perfect organization.
So what is a thallus? This is the main functional part of the body that is responsible for growth and reproduction. The simplicity of organizing this structure to some extent made it possible to master those habitats where modern plant species could not grow. The presence of thallus can be called a kind of plus.
Differences between the thallus and the body of higher plants
There are several fundamental differences in the anatomy and morphology of the body between the current spore, seed plants and such underdeveloped organisms as algae, mosses, lichens.
- The thallus is not divided into autonomic and generative organs, but is a continuous amorphous body that can take a different shape.
- In the thallus of algae, mosses and lichens, there is no differentiation on the tissue. In very rare cases, the outlines of individual groups of cells that perform similar functions are visible.
Thallus forms in different organisms
The algae thallus is also called thallus. It can be filamentous, lamellar, siphon, bushy, rounded, ribbon-like, arrow-shaped. The shape of the thallus of these organisms is quite diverse not only in shape but also in color: the body of algae can be green, brown, red, yellow or yellow-green, brown.
Lichens also have various forms of their thallus. They may be:
- Scum: thallus fuses tightly with the substrate on which it grows, and then the body of the lichen cannot be torn off without damaging the structure of this substrate.
- Leafy. Their difference lies in a small number of blades extending from one point, which easily come off the substrate.
- Bushy. They can reach large sizes in length, are often well and densely branched.
Thallus forms also exist among fungi, however, in this kingdom, the presence of groups of organisms that are characterized by a thallus is more likely an exception than a rule. They are characterized by the formation of the body with mycelium.
Is the term “thallus” appropriate to use everywhere?
Not all mosses have a thallus. For representatives of the detachments, hepatic and sphagnum mosses with thallus are characteristic almost without exception. Green mosses, which include, for example, cuckoo flax, are still divided into departments. However, they are not true stems and leaves, therefore they should be called caulidium and phyllids, respectively. Nevertheless, in spite of the simplicity of organizing such a body, one cannot call it a thallus.
What is a thallus in biology, we know and often cite algae as lower plants. However, there are exceptions, since not all representatives of these organisms are multicellular. On the contrary, many of them are unicellular or colonial structures, which it would be wrong to call thallus.
Conclusion
We examined what a thallus is, how it can be represented, and what forms it takes. Despite the simplicity of the organization of algae, mosses or lichens, it is worth noting the importance of the presence of thallus in the structure of their body. Thanks to this distinguishing feature, they were able to develop habitats where it is difficult to get comfortable with many modern highly developed plants.
Tallom performs all the functions that are inherent in the usual organs of flowering plants. It easily absorbs water throughout the surface of the body, photosynthesizes due to the presence of a special pigment. And, by the way, the diversity of color of algae is the result of various photosensitive pigments that allow these organisms to dwell at different depths, without interfering with each other in the process of light absorption. That's what a thallus is in algae.