Delving into the world of algae is fascinating when you want to know the evolutionary history of plants, and that is that the Plantae Kingdom as we know it today, has its origin in the sea. It was there, in the immense ocean that bathes a large part of the surface of the planet that welcomes us, where plant life began some 3.5 billion years ago.
Three million years later, the first terrestrial plants, bryophytes, would appear. Currently, experts have managed to identify various types of algae, belonging to different genetic lines, or if you prefer, three large family groups of these plants: each one has its own characteristics and its own preferences regarding livelihoods. it means.
What are algae?
Image – Wikimedia / Dodo
If you have ever been to the beach, or are one of those who enjoy diving, surely you have been able to see various algae on more than one occasion. But what are they? Well, they are organisms that have the capacity to perform photosynthesis and obtain carbon dioxide, which makes most species green; However, this process is carried out in a different way than plants, since they lack both xylem and phloem, that is, the vessels through which the sap is transported and, therefore, also food.
To complicate things a little more, they can be single-celled or multicellular organisms, have a size barely visible to the human eye, or grow to more than 30 meters. So perhaps you should ask yourself the following:
How does light affect algae?
Sunlight is essential for plants to photosynthesize. Is this so in algae? The answer is yes since our protagonists have photosynthetic pigments, which absorb solar radiation that comes from outside. They are, therefore, autotrophic organisms, although there are some that can be heterotrophic due to the lack of pigments, which is why they depend on other living beings.
But what about the giant algae that form marine forests, or those that live in the depths? They also capture the light of the king star, but obviously in less quantity. Because of this, they have evolved to develop additional pigments.
What are the types of algae there are?
Algae can be classified in many ways: depending on whether they are single or multicellular, depending on how they feed, on pigments… To make understanding algae easier, I have decided to classify them according to their livelihood; that is, taking into account where they get the food.
Therefore, and as we have commented before, we have:
They are cyanobacteria, the only bacteria that are capable of photosynthesis without depending on another living being. Although their cells are very, very small, just a few micrometers in diameter, they are larger than other bacteria.
There are several hypotheses and theories about when they first appeared, but it is believed that they could have started their evolution at least 3.5 billion years ago. Much later, they would allow plants to start their own evolution, thanks to the plastids.
Plastids are organelles that allow the energy of the Sun to be transformed into chemical energy, something we know as photosynthesis. Thus, both the largest tree and the smallest grass have a common ancestor which requires a special microscope to see it.
They are algae that have chloroplasts, so they perform photosynthesis. But while there are some that obtain them by living inside a cyanobacterium (something known as endosymbiosis), there are others that obtain them in other ways. Thus, these can be classified into three groups:
Image – Wikimedia / Johnmartindavies
They come from cyanobacteria. Eukaryotic algae have a cell wall that is made of cellulose, and three major lines are distinguished from them:
- Glaucophytes : are single-celled algae that live in freshwater. They have plastics called cyanols, such as cyanobacteria, and universal chlorophyll (type a). They are found in freshwaters.
- Red algae : They can be plants or protists, and they are organisms that generally live in the sea. They also have type a chlorophyll.
- Green algae : Most live in freshwater, and have both chlorophylls a and b.
Image – Wikiemdia / Grubio – 1
They are algae whose chloroplasts obtain them by living inside red algae. These chloroplasts have four membranes and type a and b chlorophyll.
- Brown algae : they are multicellular organisms and live mainly in the sea. They are the group that forms underwater forests.
- Golden algae : they are unicellular, and they mainly live in freshwater.
- Green-yellow algae: these are unicellular or colonial algae, which live in freshwater.
- Diatoms : they are unicellular, marine although there are some that are freshwater. Its cell wall is made of silicon.
- Silicoflagellates : these are unicellular algae, which live both in water and in the soil.
- Haptophytes : they are unicellular organisms that usually end up on the seabed.
- Cryptophytes : are unicellular organisms that live in marine waters.
There are other groups of organisms that obtain chloroplasts from endosymbiosis and that could not be missing in this article, such as these:
- Chlorachneous algae : they are unicellular, and appear in tropical seas.
- Euglidae : they are single-celled protist organisms that live in freshwater.
- Dinoflagellates : their chloroplasts are obtained from red algae.
What are edible algae?
If you are interested in knowing which are the most popular types of edible seaweed, it is time to answer your question. Here we tell you about three of the best known:
Dulse ( Palmaria palmata )
Image – Wikimedia / Peter D. Tillman from USA
Dulse is a type of red algae originating from the Atlantic and Pacific coasts. Its beautiful reddish color and its velvety texture make it very special food, being able to be eaten raw without problems; although it can also be included in salads.
Sea spaghetti ( Himanthalia elongata )
Image – Wikimedia / Baralloco
Sea spaghetti is a type of brown seaweed that we find on deep , rocky shorelines , almost always in rough water. In the kitchen it is used a lot to mix with rice, but it is also excellent in salads.
Wakame ( Undaria pinnatifida )
Image – Wikimedia / division, CSIRO
It is a type of brown seaweed that lives in the Pacific Ocean, where for example the Japanese use it a lot to make their famous – and very rich, by the way – miso soup. Of course, the species is considered one of the 100 most invasive and harmful in the world by the International Union for Conservation of Nature ( IUCN ).
Do you know other types of algae?