Algae and plants belong to the same plant kingdom. Thanks to algae, autotrophic pioneers, more specialized and highly organized subjects of the kingdom of Flora were able to appear.
Algae originated on our planet 800 million years ago. About 50 thousand species of these organisms are known. The study of these living organisms is the science of algology. They are primarily surprised by this group of plants with its species and morphological diversity - algae can be unicellular, colonial, multicellular. The size of individual unicellular organisms does not allow them to be examined without a microscope. Some representatives of multicellular organisms, for example, the brown macrocyst, grow several tens of meters in length. But even in these giants, the body is not differentiated into organs. By the way, the "body" of algae is called thallus or thallus.
To date, 12 types of thallus have been described: amoeboid (chlamydomonas), monadic (euglena green), coccoid (volvox), capsal, filamentous (ulotrix, spirogyra) and multi-filamentous, lamellar, siphon, siphon-clad, harophytic), sarcinoid and pseudo-tissue.
To maintain the existence and distribution of their group on Earth, algae reproduce in 3 ways: asexual with the help of zoospores or aplanospores, vegetative - division or brood branches and sexual in the form of isogamy, chologamy or conjugation.
A common feature that allowed researchers to attribute these organisms to the sub-kingdom of the Lower Plants is the presence of plastids with chlorophyll in the cells of the thallus. Therefore, plants are capable of photosynthesis. The cells of some species contain other pigments - red, brown, yellow-green, so their thalli have characteristic colors. Algae do not have organs, tissues. They absorb and release nutrients and gases thanks to the cell membranes.
Most algae live in fresh and salt water. There are those that float on the surface, and those that are attached to the bottom, but only at a depth where sunlight reaches. Those organisms that are outside the aquatic environment can settle in the bark of trees, in the snow, on the fur of animals, on rocks, in the upper layers of the soil. Algae enter into symbiosis with coral polyps and fungi, forming lichens.
Plants are a kingdom that has united eukaryotic organisms with a specific set of characteristics. The science of botany is engaged in the study of this taxon.
The main feature of plants is the presence of chlorophyll pigment in plastids that are found in cells. Thanks to him and sunlight, they can independently synthesize organic substances, are autotrophs and the basis for the food pyramid of the Earth.
Plants can be unicellular or multicellular. The body of higher plants consists of tissues: main, storage, mechanical, conductive, integumentary. In most plants, the body consists of organs - root, stem, flower, leaf, fruit. Plants can be Lower - algae and Higher - mosses, ferns, lymphoids, gymnosperms and angiosperms. The latter are represented by different life forms - grasses, shrubs and trees.
- In the number of species: less algae than plants.
- Organizational level: algae are the most primitive representatives of the plant kingdom.
- The body of algae is not differentiated into tissues and organs, in contrast to most plants.
- Most algae live in the aquatic environment, and most plants live on land.