The biological kingdoms are a way of sort out and organize the incredible diversity of life on Earth. Taxonomy is responsible for grouping living beings into these large categories, according to their common biological characteristics. This classification has evolved considerably since its beginnings with the philosopher Aristotle, until reaching modern systems that recognize between five and seven biological kingdoms.
Throughout this article, we are going to delve into everything you need to know about the biological kingdoms, their characteristics, types, and how this system has evolved over time. Join us on this fascinating journey through the diversity of life!
Origin and evolution of biological kingdoms
The classification of living beings has been a constant concern for scientists and nature scholars. Since ancient times, different formulas have been attempted to better understand how living beings are related to each other. Below, we explain the most relevant stages in the evolution of the biological kingdoms:
- Two Kingdoms System: Attributed to Aristotle in the 4th century BC. In this system, living beings were divided into only two large kingdoms: Animalia y PlantThe distinction was based on the presence of capacities such as movement and perception (typical of animals) as opposed to attachment to the ground and photosynthesis (typical of plants).
- Three Kingdoms System: Proposed by Richard Owen in the 19th century, added a third kingdom, Protists, which included microorganisms that could not be easily classified as animals or plants. This was of great relevance for studying microscopic organisms with mixed characteristics.
- Four Kingdoms System: As research in microbiology progressed, the scientist Herbert Copeland He proposed a system with four kingdoms: Animalia, Plant, protozoa y monera, the latter to include prokaryotic organisms (without a nucleus).
- Five Kingdoms System: In 1969, Robert whittaker He proposed the five-kingdom system which included fungi in a separate kingdom called FungiThis system remained in force for several decades.
- Six Kingdoms System:In the second half of the 20th century, with the advance of molecular biology and the discovery of key genetic differences, Carl Woese and G. Fox They proposed a system of six kingdoms: B, Archaea, Protists, Plant, Fungi y Animalia.
- Seven Kingdoms System: Finally, a seven-kingdom model was arrived at thanks to the research of Thomas Cavalier-Smith in 2015, which introduced the kingdom Chromista.
This latter system is still used today, although scientists continue to refine the details of the classification, especially in the more complex kingdoms such as Chromista y protozoa.
The biological kingdoms
Today, seven biological kingdoms are widely recognized. Each of them groups living beings based on their life forms, cellular characteristics and their evolution. Below, we explain each of these kingdoms.
Kingdom Bacteria
El reino B It is composed of organisms prokaryotes, characterized by the absence of a defined cell nucleus. They are unicellular and are found in almost all habitats on Earth. Bacteria can be classified according to their dyeing characteristics into Gram-positive (thick cell wall) and Gram-negative (thin cell wall).
Key features:
- unicellular
- Asexual reproduction
- Presence in aquatic and terrestrial environments and even inside other organisms.
- They form colonies and are important for biogeochemical cycles.
Bacteria can be both beneficial and harmful to humans. For example, Lactobacillus are important for the production of yogurt, while the Clostridium botulinum It causes botulism.
Kingdom Archaea
The archaea belong to a group of prokaryotic organisms which, at first glance, appear similar to bacteria, but differ in their genetic structure and biochemistry. They are generally found in extreme environments such as hot springs, underwater volcanic areas and very saline environments.
Key features:
- They live in extreme conditions (high temperatures, high salinity).
- Its metabolism may be chemosynthetic.
- They do not have peptidoglycan in their cell walls.
Archaea are essential to understanding extreme biochemistry and how life can thrive in harsh conditions.
Kingdom Protozoa
El reino protozoa encompasses organisms eukaryotes unicellular organisms that share characteristics of both animals and plants. They are the most primitive of the eukaryotes and constitute a paraphyletic group, which means that they include the common ancestor but not all of its descendants.
Key features:
- Unicellular and eukaryotic
- Mobility by flagella, cilia or pseudopodia
- Heterotrophic nutrition (some are predators, others saprophytes)
Protozoa include some pathogens such as Plasmodium, responsible for causing malaria.
Chromista Kingdom
El reino Chromista was proposed by Thomas Cavalier-Smith to include organisms previously classified as protists o FacilitiesIt groups together a wide variety of organisms, some of which can carry out photosynthesis.
Key features:
- They can be unicellular or multicellular.
- Photosynthesis using chlorophyll c.
- Some species (such as diatoms) play a very important role in aquatic ecosystems.
Among the best-known chromists are diatoms and brown algae, both essential for primary production in aquatic ecosystems.
Kingdom Plantae
El reino Plant It is made up of organisms eukaryotes multicellular that perform the photosynthesis to obtain energy. They are autotrophs and play a key role in the production of oxygen and in the food chain.
Key features:
- They are multicellular organisms.
- They carry out photosynthesis using chlorophyll.
- They have a cell wall made of cellulose.
- Asexual and sexual reproduction.
Examples of plants range from mosses and ferns to large trees such as redwoods.
fungi kingdom
El reino Fungi It is composed of mushrooms, organisms eukaryotes that do not carry out photosynthesis and feed mainly on decomposing organic matter.
Key features:
- They are heterotrophs and decomposers.
- Unicellular (yeasts) or multicellular (mushrooms).
- They have chitin cell walls.
- Sexual and asexual reproduction (spores).
This kingdom includes everything from edible mushrooms to molds and yeasts, many of which are vital to the ecology of organic matter decomposition.
Animalia Kingdom
El reino Animalia brings together the organisms multicellular, eukaryotic and heterotrophic that have the ability to move at some stage of their life and feed on other organisms.
Key features:
- Multicellular.
- Reproduction is mainly sexual.
- They present differentiated tissues and, in many cases, complex systems such as digestive, respiratory, etc.
- Division between vertebrates and invertebrates.
This kingdom includes an immense diversity of life forms, from insects to large mammals such as whales and humans.
In short, the study of biological kingdoms has allowed us to better understand the diversity and evolution of living beings. As science advances, we are likely to continue discovering new ways to classify and understand life on our planet.