Algae

• Algae can be found in a wide range of habitats, including oceans, rivers, and lakes, as well as ponds, brackish water, and even snow. Algae are typically green but can be found in a variety of colours. Snow algae, for example, contain carotenoid pigments in addition to chlorophyll, giving the surrounding snow a distinct red colour.
• Algae are chlorophyll-containing, simple, thalloid, autotrophic, aquatic plants.
• They are found in moist stones, soils, and wood, as well as in the presence of fungi and animals.
• Algae are common near or inside bodies of water because they require a moist or watery environment. They share structural similarities with terrestrial plants, a significant group of photosynthetic organisms.
• The similarities stop there, however, because algae lack many structural components found in plants, such as true stems, shoots, and leaves.
• They also lack vascular tissues, which allow vital nutrients and water to circulate throughout their bodies.
• Example: Lichen is the combination of algae and fungi, Algae grow on the sloth bear’s body.

Characteristics

Some of the general characteristics of algae are listed below.

• Algae can photosynthesize like plants and have specialised structures and cell organelles found only in animals, such as centrioles and flagella.
• Algae are photosynthetic organisms that can be unicellular or multicellular in nature.
• Algae lack a well-defined body, so structures such as roots, stems, or leaves are absent, and Algaes can be found anywhere there is enough moisture.
• Algal reproduction takes both asexual and sexual forms. Spore formation is used in asexual reproduction.
  Algae are self-contained organisms, though some can form symbiotic relationships with other organisms.

Reproduction 

• Algae reproduce through vegetative, asexual, and sexual means.
• Asexual reproduction occurs through the formation of flagellated zoospores, which germinate and give rise to new plants. Palmella Stage-During this stage of asexual reproduction, the spores colonise and resemble the algae Palmella. For example, Ulothrix and Chlamydomonas.
• Vegetative reproduction is accomplished through fragmentation, with each fragment developing into a thallus.
• Sexual reproduction occurs through the fusion of two gametes; if the gametes, with or without flagella, are similar in size, they are isogamous; if they are dissimilar in size, they are anisogamous; and if the female gamete is large, non-motile, and the male gamete is smaller, motile, the gametes are referred to as
• Isogamous gametes with flagella are found in Chlamydomonas and without flagella in Spirogyra, anisogamous gametes are found in some Chlamydomonas species, and oogamous gametes are found in Volvox and Fucus.

Algae, bryophytes, pteridophytes, gymnosperms, and angiosperms are all members of the plant kingdom. The first land plants appeared around 470 million years ago, and a spectacular amount of plant biodiversity has evolved over the aeons.

The plant kingdom is thought to play one of the most important roles in human life. Human survival would be impossible without the existence of plants. It is an open secret that plants are the primary source of the various vital components required for the survival of life on Earth.

The most important component is oxygen, without which most species would become extinct. This oxygen is released by plants during the photosynthesis process, in which green plants use the energy obtained from sunlight to help convert carbon dioxide into oxygen. This oxygen that humans have access to is critical for breathing and survival.