Although not all people know the definition of the word animal, almost everyone knows how to differentiate them from other living beings. The Animal or Animal Kingdom comprises all those organisms called animals, beings recognizable by the characteristics of their movements and their reactions to the environment. It should be noted that animals are also known as metazoos.
Continue reading this article to learn more about what the Animal or animal kingdom is, its characteristics, classification and examples. Don’t miss it.
Characteristics of animals
Animals are living beings who perform the functions of nutrition, relationship and reproduction. Many are very complex organisms, but others are distinguished by the relative simplicity of their conduct, as in the case of jellyfish. The characteristics of the most outstanding animals are the following that we will explain.
They are multicellular organisms
All animals are made up of several microscopic cells that do not have a rigid cell wall. With the exception of sponges (yes, sponges are animals), cells are organized in tissues that in turn make up specialized organs such as heart or brain.
Many animals establish the shape of the body in the early stages of its development, but others undergo radical transformations translated into a process called metamorphosis. That’s the case with butterflies.
They’re heterotroph organisms.
Animals feed on other organisms because they are unable to produce their food from their own organic substances. Almost all animals are equipped with a useful mobile mouth to hold and/or chew food.
They can feed actively as most of those who move, or passively, do when they take advantage of the food particles suspended in the middle and pick them up when they pass near their mouth.
Some other animals feed by filtration; there is no better example of this feeding process than that performed by whales with beards, which swim and filter water to capture small organisms.
They make gas exchange
Animals breathe and this involves a process of gas exchange between the inside and the outside of cells. This requires oxygen to convert food into energy, a process that fires carbon dioxide. Gas exchange takes place in varied ways.
Some animals do it through:
- Branch tube system.
- Type of blood circulation that carries the gases through the body.
They have a sensory system
With the exception of jellyfish, the animals have networks of nerve cells that react to external stimuli. They have a structure called a receiver that detects a change in the environment, a driver through which the signal is moved to the center of the coordination and an effectr, that is, an organ responsible for responding to the stimulus. Most animals have organs of the senses that are concentrated in the head area.
Exhibised mobile behaviors
All animals are able to make movements and many can slide, rebuke, run, fly, etc. Maybe mussels spend most of their lives hooked on a rock, but even there they run water pumping movements. The modes of displacement are diverse.
For example, some marine animals do so through body ripples, others by expelling a jet of water.
Classification of animals
The classification of the metazoa is very varied but it can be said that, basically, there are vertebrate and invertebrates animals. Of the more than 10 million animal species that scientists estimate in the world, 97.4% are invertebrates and only 2.6% are vertebrates.
Examples of the animal kingdom
Now that you know how the animal kingdom or animalia is classified, let’s see what concrete examples are in each of the groups and what its characteristics are.
Scientists have identified only about 50,000 vertebrate species, but they still make up a very diverse group. There are 5 groups of vertebrate animals:
- Fish: The fish were from the first vertebrates as they evolved from animals with spine about 500 million years ago. They are animals completely adapted to the aquatic environment, breathe through gills and move thanks to the fins. They may be cartilaginous (carlage skeleton) or bone (calcifiedskle).
- Mammals: It was the last group of animals to appear on Earth, about 65 million years ago. The more than 5,000 species of mammals have warm blood, give birth to living off, and feed on breast milk during their early development. They are adapted to diverse habitats.
- Aves/Birds: they are actually homeoterous reptiles and are believed to descend from the dinosaurs. There are about 10,000 species of birds to date living worldwide except in polar regions of extreme temperatures. Most birds have the power to fly, but some, like chickens and ostriches, can’t do it. Some others can dive and even swim. They’re oviparing animals.
- Reptiles: They were the first vertebrates to survive outside the water because of eggs that could be hatched on mainland. The group of reptiles includes turtles, lizards, snakes, crocodiles and tuataras. They are cold-blooded animals with a skin covered in hard, dry scales. They are also able to regulate their temperature.
- Amphibians: These vertebrates are curious: they have cold blood as do reptiles, but their skin is smooth and has four legs. They are characterized by occupying terrestrial habitats and spawning in fresh water.
These animals are the oldest animal life form on the planet. They are classified in about 30 edges and therefore are the largest group of animals. Although they are devoid of bone skeleton, many have some kind of internal or external skeleton.
They multiply by sexual or asexual reproduction and some have both sexual, male and female organs. Some of the best-known invertebrates are:
- Seafaring cornals