Kelp is a delicious ingredient that many people like, especially when it is made into shredded seaweed cold dishes, paired with garlic and chili oil. It is very delicious, and it can also be boiled, fried, and made into soup. Many people may have thought that kelp is an aquatic plant, which is usually classified in biology. However, upon closer examination, kelp cannot be considered a plant because its relationship with certain animals is closer than with plants.
When life first emerged on Earth, it was mostly primitive microorganisms. At that time, there was no distinction between animals and plants. Later, some of these organisms began to use solar energy as their energy source, while others consumed other organisms as their energy source. This differentiation led to the emergence of the embryonic forms of animals and plants. As various organisms emerged, animals and plants began to differentiate, and the ancestors of modern plants, such as green algae, emerged, but kelp did not have an ancestor among them.
Kelp is a type of brown algae, belonging to the flagellate organism that preserves photosynthesis. Some people also believe that kelp belongs to the “vesiculite kingdom”, but in fact, both belong to the vesiculite organism, and their genetic relationship is very close. The paramecium, which we have learned in our middle school biology textbooks, belongs to the vesiculite organism that abandons photosynthesis. Therefore, the relationship between kelp and the more primitive animal, paramecium, is closely related, and it is closer to the plant-like organisms purified by various organisms.
The reason why we often consider kelp a plant is that it retains its photosynthetic function and has roots that can fix growth. This is indeed very similar to other plants, and biology also refers to organisms that can fix life and are autotrophic as plant kingdom organisms. Therefore, if we only define kelp from this perspective, it can indeed be called a plant. However, in terms of its evolutionary process, physiological characteristics, and its own cell structure, they are very different from common woody and herbaceous plants. For example, most plants have roots, stems, and leaves, but algae do not have real roots, stems, or leaves, nor do they have vascular bundles.
Although the broad leaves of kelp are similar to those of plants, usually kelp only has one leaf (not considered a leaf in biology), while most plants have many leaves. The characteristics of kelp’s “leaves” are also different from those of other plant leaves in terms of structure and function. Although their energy acquisition mainly relies on photosynthesis, there are fundamental differences between them! This is because when the ancestors of kelp were still ciliates, they devoured a type of organism capable of photosynthesis, and the two basically merged into one. Therefore, kelp can be said to be a combination of animals and plants, with chloroplasts containing organisms coexisting within the kelp, forming the kelp’s chloroplasts, or it can be said that a plant capable of photosynthesis resides within the kelp’s body. However, this “plant” lacks autonomy, and its growth and physiological behavior are already dominated by the kelp itself, forming a phenomenon of symbiotic and symbiotic unity. It can also be said that they have long merged into one, becoming a living organism.
In short, there are actually too many differences between kelp and other common plants. There are fundamental differences between the two from the early stages of evolution, but from some surface features, kelp is more like a plant. Therefore, in 2005, biologists placed kelp under the newly added phylum Microcystis, which is a eukaryotic organism with photosynthesis unique to plants.
