Animalia Kingdom: Characteristics, Classification And Examples
The kingdom Animalia, also called Metazoa, is a large group of organisms that are animals, among which we find human beings. The term animal comes from the Latin animalis, which means “that takes the air”, “that has a soul”.
Most of them can move and reproduce sexually, however there are some exceptions, which have contributed to the idea that some species, such as sponges and sea lilies, are considered plants.
We are going to see the characteristics that define this kingdom, with its particularities, and some of the groups that make it up.
Although the ways in which they feed, anatomy, reproductive behaviors and other aspects differ greatly, most animals have a series of characteristics in common:
1. Multicellular
They are organisms made up of more than one cell. These cells are organized into specialized tissues, constituting organs and systems, which allow them to carry out differentiated functions. Thanks to this, animals have a nervous system and also muscles, which allow them to carry out different behaviors.
2. Heterotrophic nutrition
Unlike plants, which carry out photosynthesis to generate their own food, animals They depend on other organisms to survive Basically, this type of nutrition involves transforming organic matter into the nutrients that the body needs.
The food source can be very varied depending on the species. There are herbivorous animals, such as cows, that feed exclusively on plants. Others, however, are carnivores like lions, feeding on other animals. If it feeds on both animals and plants, the animal is omnivorous.
There are other categories that refer to more specific types of food: nectarivores (nectar from flowers), insectivores (insects and other arthropods), xylophobes (wood)…
3. Aerobic metabolism
The vast majority of animals need oxygen to carry out metabolism and maintain basic functions One of the few exceptions to this is the case of loricifers, which can live in environments where there is no oxygen and survive.
4. Playback
In most cases, animals carry out reproduction sexually. This implies that there is a differentiation into two sexes: males and females. The advantage of this type of reproduction is that it allows genetic variability, however it has the drawback that the process is very slow, since the sexual partner must be found, courtship begins, fight for her if necessary and carry out the sexual act, all requiring energy.
There are some animals that reproduce asexually like sponges or worms, which can multiply by bipartition, that is, breaking into two and creating a new individual from the original.
5. Sensory capacity
Because organs can carry out different functions, animals have several types of senses Apart from the five generally best known (smell, taste, touch, vision and hearing), there are other senses with very specific evolutionary purposes.
For example, snakes have infrared sensors with which they identify the heat of prey. Some insects, such as moths, can sniff out pheromones and locate a potential breeding partner several kilometers away. Sharks have electrical sensors and capture electrical fields, locating prey and sensing how fast they are going or if they are camouflaging themselves.
Most organisms in the kingdom Animalia They have a symmetrical anatomy, that is, their body can be divided into two equal parts from an axis Depending on the type of symmetry, animals can be divided into bilaterally symmetrical and non-bilaterally symmetrical.
7. Locomotion
Representatives of the Animalia kingdom can move on their own, and there are several ways in which they can do it. Some, like starfish, have hundreds of small feet on their extremities that allow them to move along the seafloor. Others, such as humans and other mammals, move using their extremities, such as legs and fins.
Some animals, upon reaching adulthood, stop moving. Some examples are corals and anemones.
Classification and edges
The Animalia Kingdom comprises more than two million living species, which have been grouped into more than 30 phyla, categories that serve to classify all this biodiversity. Some of the best known are detailed below:
1. Chordates
Its name comes from the fact that it has a dorsal chord, a dorsal neural tube or tail at some point in its embryonic development. It is the third phylum with the most described species, the majority being vertebrates (animals with an internal skeleton), and more than half are fish.
Some groups of chordates are all vertebrates, such as mammals, spiny fish, reptiles, amphibians and birds, as well as some marine species such as cephalochordates and hagfish.
2. Arthropods
They are invertebrate animals equipped with an exoskeleton and articulated appendages, and are made up of insects, arachnids, myrapods and crustaceans. It is the animal phylum with the most described species, representing 80% of known animal species.
Thanks to their great adaptability, they come in multiple shapes and sizes, with one of the largest arthropods in history being the extinct meganeura or the giant dragonfly, which could reach 70 cm.
3. Poriferous
Sponges are included in this phylum, which unlike what many people believe, are part of the Animalia kingdom. For the most part they are marine and have the peculiarity that they are sessile (they are fixed to the ground) and do not have authentic tissues, which is rare in the animal kingdom.
4. Mollusks
Among the mollusks are bivalves, squid, octopuses, snails and slugs. They are soft animals without an internal skeleton but they may have a shell to protect themselves
They are considered a phylum that has known how to adapt evolutionarily very well, being of marine origin but that came to conquer terrestrial habitats. They have been found in places with extreme temperatures, such as polar and tropical waters.
5. Annelids
They are worms with rings, like leeches and earthworms These rings are called metamers, which each have some repeated organs and which, if the worm divides, allow the survival of new individuals.
They have both sexual and asexual reproduction. In the case of sexual species, there are species that have two differentiated sexes while others are hermaphrodites. Asexual reproduction occurs by excision, splitting in two.
