- What are animals?
- General characteristics of animals
- Vertebrate animals and invertebrate animals
- Wild animals and domestic animals
- Carnivorous animals, herbivorous animals and omnivorous animals
We explain everything about animals, their characteristics and how they are classified according to their body, their relationship with humans and their diet.
What are animals?
Animals or metazoans are living beings that make up the animal Kingdom (animalia), one of the four kingdoms of living beings eukaryotic (i.e., organisms that have cells with nuclei), and which are distinguished from the floors, mushrooms Y microorganisms. In general, animals are living beings endowed with movement own and autonomous metabolism based on the breathing and a nervous system that allows them to interact with their environment.
As a whole, animals are extremely diverse and are adapted to all habitats of the planet, establishing relationships of different kinds among themselves and with other living beings. The human being also belongs to the animal kingdom, but since it is the only living being endowed with its own consciousness and language articulated that is known, it is generally given a separate philosophical category within the set of animals. Seen in this way, a human being would be an animal endowed with language.
The animals appeared on the face of the Land approximately 542 million years ago, during the so-called "Cambrian explosion" or Cambrian evolutionary radiation.
It is unknown what exactly were the reasons for such a massive and abundant diversification of the life. However, it is known that of the about 20 phyla (phyla) or groups of species animals known until now, at least 11 had their origin in that specific time, that is, that the first and oldest species arose there multicellular animals, whose descendants can still be found on the planet.
The word "animal" comes from the Latin animals, translatable as "being endowed with breath" (that is, with encourages), that is, “breathing creature”. The science who studies animals is called zoology, and it is a specific branch of biology, which enables classify animals according to different categories, attending to traits such as their behavior, anatomy or even their relationship with the human being.
General characteristics of animals
The main general traits of animals are:
- They are eukaryotic living beings, that is, they have cells equipped with a cell nucleus well defined, in which the Genetic information gathered; and also multicellular, that is, whose bodies are made up of more than one cell.
- Unlike plants and fungi, animal cells They have no cell wall (but a more flexible plasma membrane), no vacuoles, no plasmodesmata.
- Your nutrition is heterotroph, that is, they obtain their nutrients from the organic material of other living beings, unlike plants (autotrophs). Therefore, animal cells also do not have chloroplasts (organelles for photosynthesis), otherwise lysosomes.
- Your metabolism is aerobic, that is, it requires a continuous supply of oxygen (since it obtains its energy from the oxidation of molecules organic). The process of capturing oxygen from the environment (either air or water) is known as breathing and therefore all animals breathe.
- They are endowed in the vast majority of cases with their own autonomous mobility, that is, they can change their environment at will, thanks to the presence of motor organs such as cilia, legs, fins, wings, among others.
- They are sexual species, that is, of reproduction predominantly sexual. This type of reproduction requires a male and a female to produce a new individual, through the union of their well-differentiated sex cells or gametes. There are, however, some animal species capable of asexual reproduction in certain circumstances.
- Their bodies are made from collagen, a protein structure that is found in all the fibers of its tissues. The latter, in addition, usually have a very high level of differentiation and specialization.
- Their bodies have bilateral symmetry: they can be divided with a transverse line into two identical and corresponding halves. The exception to this rule is made up of a few primitive phyla such as the porifera and echinoderms.
Vertebrate animals and invertebrate animals
Invertebrate animals do not have vertebrae or a skull.
The kingdom of animals can be differentiated into two large groups, based on the presence in their bodies of an internal skeleton equipped with a skull and a vertebral column. Thus, we can talk about:
- Vertebrate animals. Those who have an internal skeleton with a spinal column and a skull, all made of osseous tissue (bone) and designed to protect the nervous system: the spinal cord and the brain. Their bodies, furthermore, are easily divided into three segments: head, trunk, and limbs.
Examples of vertebrate animals are mammals, the fish, the reptiles, birds and amphibians. Vertebrate species include humans, dogs, horse, the alligator, the mouse, the bat, the platypus, the birds, the frogs, among many others.
- Invertebrate animals. Those that have an external skeleton (exoskeleton) as an armor made of chitin. Therefore, they have neither vertebrae nor a skull, and are mostly oviparous animals (they hatch from eggs). In evolutionary terms, they are more primitive than vertebrates.
Examples of vertebrate animals are insects and arthropods, molluscs, sponges, cnidarians, annelids and echinoderms. Invertebrate species include sea urchins, octopuses, the bees, scorpions and spiders, earthworms, starfish, among many others.
Wild animals and domestic animals
Depending on their relationship with humans and society, animals can be classified into two groups, depending on whether they are domesticated or not, that is, whether they have adapted to peaceful coexistence with humans, or not. Thus, we can distinguish between:
- Wild animals. Those who do not know the presence of the human being or who are not at all used to it, and who therefore react to it with aggression or other instinctive behaviors. The animals that inhabit the nature they are all wild.
Examples of wild animals are: Wolves, the lions, the Whales blue, the condors, the rhinos, the hippos, the penguins, the polar bears, most of the snakes, and all those animals that exist within human society only in zoos.
- Domestic animals. Those that have adapted over time (and the direct intervention of our species) to interact with human beings and even to depend on them, occupying a stable place within civilization. companion animals, farm animals and the trained animals are all domestic.
Examples of domestic animals are: the cow, the dog, the cat, the chicken, the sheep, the goat, the horse, the pigeons, the hamsters, some species of fish and turtles, among others.
Carnivorous animals, herbivorous animals and omnivorous animals
Animals are heterotrophic beings, which must consume the organic matter of other living beings in order to survive, that is, they feed on other living beings and organic matter. But not everyone does it the same way, and depending on their food preferences, it is possible to classify them into three categories:
- Carnivorous animals. Those whose diet consists strictly or almost strictly of meat, that is, the body of other animals. This means that the vast majority are predators (which attack and eat other animals) or scavengers (it feeds on their carcasses once the predators have finished eating). Carnivorous animals often have sharp teeth to tear meat and limbs with sharp claws to help when hunting.
Examples of carnivorous animals are: the lion, the wolf, the tiger, the shark, the serpent, the eagle, among others.
- Herbivorous animals. Those whose diet consists strictly or almost strictly of plant and fungal substances, that is, of parts of the body of plants and fungi or of materials produced by them. Herbivores typically have flat teeth with strong molars, to grind up plant matter, as well as multiple stomachs to digest plant matter more efficiently.
Examples of herbivorous animals are: the cow, the horse, the sheep, the giraffe, the ox, the rhinoceros, the butterflies, among others.
- Omnivorous animals. Those whose diet is diverse, adaptable to availability or occasion, and therefore combine plant-based foods with animal-based foods.They are animals with a changing or multiple diet, which can play different feeding roles at the same time, being herbivores and carnivores at the same time. Omnivores often have a mixed dentition, combining sharp teeth for tearing and blunt molars for crushing.
Examples of omnivorous animals are: the human being, the monkey, the rats, the pig, the bear, the fox, turtles, crows, among others.