Animal

Description

Technically, the animals are pluricellular organizations Eucaryotes (except the Myxozoa ) what differentiate them from the Bacteria and of the Protista and deprived of Chloroplastes (Hétérotrophe S), which distinguish them from the vegetable and Algue S. They are also distinguished from the Mycota . They are the only living organisms which pass in a stage of their development by a Blastocyste. They are suited to the movement, sometimes only in larval form (case of the sponges and many invertebrates Benthique S fixed at the substrate). They form the reign Animalia, subdivision of the field Eukaryota.

The animals (or Métazoaire S) are one of the types of Eucaryotes to be itself developed on a mode Pluricellulaire, like the Plante S, some Champignon S, and the brown algas in opposition to the Unicellulaire S which gather yeasts or mushrooms, certain algae, of the protozoa (and generally all eucaryotes which are not animals, plants or mushrooms) as well as the being alive gathered within the Prokaryota, composed of the Eubacteria and Archaea.

Organizations

One distinguishes, according to their complexity of internal organization, four groups or levels. Simplest are the animals with cellular organization , i.e. these organizations consist of an aggregate of cells differentiated and specialized like the somatic cells and those responsible for the reproduction. If it is the typical level of some Protozoaire S coloniaires, certain scientists classify the sponges in this group.

Of an organization slightly more complex, one finds the organizations with organization cell-fabrics or diploblastic, i.e. they are formed starting from cellular layers with definite function. There can be between these layers a matrix which does not constitute a genuine cellular fabric and which does not contain any differentiated body. Some classify sponges in this group but the jellyfishes are a better example. One distinguishes then the organizations where the fabrics form bodies such as for example for the Plathelminthes and where one finds well defined ocelles, a digestive tract, and reproductive bodies. And finally are the organizations with body-systems which represent the major part of the junctions. They have one or more circulatory systems for several vital fluids, a dedicated respiratory system, a digestive system, a nervous network allowing perception, etc Annélides are one of the simplest examples.

Biology

Like all the living organisms, the animals need Eau, of a Comburant which is exclusively the Oxygène for these species, and of organic matters coming from other organizations because they cannot produce it by themselves starting from molecules not coming from the alive one. It is said that they are chimioorganotrophes and when the organic matter comes from another animal, one speaks about predation. This food meets three aims: to provide the substances which are used to create other cells; to produce substances useful for the organization (bone, hairs, tears, odors), and especially to provide energy.

As for all the living organisms, water is element of which the animals have the most evil to occur. In addition to the fact that the cell S primarily consist of water, water is necessary to the majority of the biochemical reactions where it is used as Solvant. But, moreover, it is used for the evacuation of the nitrogenized waste produced by the metabolism of the proteins which must be eliminated. The animals, like the other species even nonwatery, are also confronted with the problems involved in the Osmorégulation.

They need to get their food while moving or by catching it, and thanks to a digestive Système, to dissociate the organizations in substances necessary which theirs are useful, then to assimilate them. The acquisition of oxygen is used to oxidize carbohydrates to produce energy chemical or muscular, is thus also a priority for the majority of the animals. The majority of the species lay out of a Respiratory system to absorb oxygen. Oxygen, water and the various substances are brought towards the cells and the useless by-products are evacuated (Excrétion) thanks to various circulatory systems. The problems arising from the various mediums suppose specific adaptations. Thus the acquisition of oxygen for a terrestrial organization is less difficult than the acquisition of water. The reverse is true in an aquatic environment. To acquire these substances essential with the life, the majority of the animals use bodies of perception. They also use their direction to flee their predatory.

The functions of reproduction are also important at the animals which are mainly Sexué S, but certain species as the hydre can also reproduce in a manner Asexué E (by budding in its case).

Biodiversity of the animal world

Elementary forms

Sponge (cellular colony)

The animal cells are Hétérotrophe S, i.e. they must eat to survive, contrary to the plants. The survival of an animal passes by a constant concern: how to eat? The strategy of the sponges simply consists in filtering the water which crosses them, to capture preys there. This strategy requires neither complex structure, nor coordinated movement.

The sponges (Porifera) form the simplest organization: they are colonies of practically undifferentiated cells, without real internal structures, nor operation. They are animals without Nervous system nor digestive Tract. Their body is formed only by two layers of cells (Ectoderme and Endoderme).

Polyp: hydres, coral and jellyfish

The passage of a level of the type sponges with an organization of the anemone type always answers the constant question: how to eat? The formula developped at the point by this group consists in pushing food towards a belly (gastric cavity) where it could be digested without running away itself. This innovative strategy makes it possible to nourish larger preys (what the sponges cannot filter). In the progressive acquisition of animal functionalities, this evolution supposes two things: the cells specialize (with the acquisition of cells nervous and muscular allowing coordinated movements) and the organization gains the capacity to take a definite form (Morphogénèse), so that effective tentacles can push their prey towards an effective gastric cavity.

Worm (mobility and digestive tract)

The organization of the type worm is a new answer brought to the key question of the animal kingdom: how to eat? The basic strategy of the organizations of the type “worm” (vermiform) is to move to go to seek food, instead of waiting until it passes to range. This strategy in particular makes it possible to exploit organic waste, which can be with high food value, but do not move.

Passed the course of sponges and the polyps, all the complex organizations are Bilatérien S, which derive from a fundamental diagram: the tube. The development is organized around an axis head/tail on the one hand, and back/belly on the other hand. These two axes lead to an overall plan where the sides right and left tend to being symmetrical, from where them name of bilatérien.

The simplest worms mark an additional qualitative stage compared to the Cnidaire S: the nervous cells are organized in a coherent nervous system, prototype of what will become the brain in the higher animals. It is this capacity of displacement and reaction to the environment which makes consider that the vermiform degree of organization is the first stage really " animal".

The second major invention of the worms (absent in the flat worms) is the presence of a food channel and a digestive function: at an end, a mouth absorbs food, with the other, an anus excretes waste. Between the “external tube” which forms the skin (Ectoderme) and the “interior tube” (Endoderme) which is the food channel, an intermediate fabric, the Mésoderme, can develop and form increasingly complex internal bodies.

The invention of the digestive tract starting from the ancestral gastric cavity twice seems to be made. At the Protostomien S, the two openings of the food channel are formed starting from the Blastopore, which the lips approach to form a channel by longitudinal welding. At the Deutérostomien S, the opening of the Blastopore becomes the Anus, the food channel being formed by a later boring which will evolve to the mouth.

The towards are at the origin of one second major invention of the evolution: the segmentation (Metamerism). This invention also seems to be made in several different branches.

Radiative explosion of the vermiform ones

The discovery of the digestive tract and the capacity to move (while crawling) was the gaining formula: the vermiform organizations are rather general-purpose, and can be used as a basis for very varied lifestyles. It is what is called a radiative Explosion: starting from a common basic diagram, the forms take divergent ways, as if they radiated starting from a central explosion. All the other more advanced diagrams of organization are based on this fundamental type: they are a little complicated worms.

The independent groups which raise of the vermiform level of organization are:

towards dishes, in particular Planar S, of particularly simple organization;
towards rounds, or nematodes, are more typical representatives of not segmented worms;
the towards segmented are elementary representatives of the form of segmented organization.

The level of organization of the vermiform type is not maintained at all the bilatériens. Organizations as the tunicates resemble more the sponge shapes or corals that with worms, which is generally the case of the forms turning over to a vegetative lifestyle.

Lastly, this form of organization becomes more and more complex according to three ways, of which the hard parts will be able to leave fossils:

the Molluscs, which acquire a rigid structure with a shell;
the Arthropods, which organize themselves inside a exosquelette;
the Vertebrate ones, which is organized on the contrary around an internal skeleton.

Higher forms

Molluscs

The mollusc S evolve/move starting from an organization of the type worm . The functionality which seems to have conditioned primitive molluscs appears to be the shielding, making it possible to protect itself from the predatory credits: the acquisition of plates limestones protecting the back. These primitive molluscs were to thus resemble Polyplacophore S (a kind of snail which can roll itself in ball like a hedgehog or a woodlouse), but this type is now very marginal.

The molluscs include/understand the following important classes:

the gastropodous (family of snails), which continue to crawl.
the bivalvular (family of the shells), which became sedentary.
the cephalopods (family of octopuses), which learned how to swim.

Arthropods

On the general formula of the worms, the Arthropode S superimposed several innovations:

the segmentation, shared with many other organizations, which consists in lengthening the body by repeating of the same segments anatomy.
formation of locomotor legs. Tentacles playing the part of legs are present at certain towards.
the transformation of the skin into a rigid skeleton, the exosquelette.

This gaining formula corresponds to the general form of the millepede. It was immediately at the origin of a new radiative explosion, which explored various formulas to transform such or such group of legs into jaws, antennas, specialized legs, or to let them regress in the tail.

The junction of the arthropods is by far that which has the most Espèce S and the most individuals of all the Animal kingdom. One counts more than one million and half of current species of arthropods. The key question which seems to have structured its distribution is: how much legs is necessary it to move?

Insects

The Insecte S belong to the Arthropode S. Their body is composed of three parts: head, thorax, abdomen. They have six legs, four wings and two antennas. This description is a general information, the evolution having made that by specialization, certain elements can be atrophied.

The insects are pledged with the emerged grounds. One does not know marine insects. One finds them under almost all the climates, of hottest with coldest.

Towards swimmers: fish

The essential functionality which initially structured this order was the capacity to swim in water (what could do neither the primitive molluscs, nor the primitive Arthropode S).

But this capacity did not lead to a radiative explosion: by itself, it does not give a sufficient functional autonomy so that the organizations can specialize in a very free way.

The history of this line appears hard: the progressive discovery of the head and the jaw, then the exploration of the members until the stage tétrapode, and finally, the conquest of the air environment, leading to the radiative explosion of the finally general-purpose sauriens.

Tétrapodes

The Tétrapode S, animals with four members, had a radiative explosion after having conquered the capacity to move on the dry land. However, certain groups of species like the Cetacea or the snakes keep, following their evolution, only vestiges of members.

The tétrapodes gather really different animals of size, microphone-mammals with the Blue whale which is the largest known animal of all times but they represents only one negligible part at the same time of the alive species (to the more 2%) and of the Biomasse. In spite of this, they are among the species the best known ones of the man of which this one formed part. Although the man has, since Aristote at least, tried to gather the various species following of the homogeneous groups, he managed to include/understand the phylogeny of this group only at the end of the 19th century. It is considered today that this group is composed of the Amphibien S of the Sauropsida of which the Reptile S and the Oiseau X and the Mammifère S.

Amphibians

Reptiles

Birds

Mammals

The radiative explosion of the Mammalian the S, most recent, followed the disappearance of the dinosaurs.

The mammals are generally identifiable by their skin, at least partially, covered of hairs. The fact that the females nurse their young people is also a characteristic of this group.

Simplified classification of the animal types

Problems related to the animal kingdom

Various sciences aim at studying the animal world for example the Zoologie which break up into a multitude of specialities, medicine Vétérinaire, but also in a derived way the Paléontologie, the Biologie, and the Microbiologie and the Agronomie for its economic implication .

Disappearances of the species

Since the appearance of the life, many species disappear. After some Cataclysm S, it could there have massive extinctions, followed by radiative explosions, i.e. a strong increase in new species.

The man while trying to domesticate nature, by supporting an inevitably restricted number of species, tended to reduce the number of Biome S. In addition, the Pollution S generated by industry and the Consumer society also cause to destabilize the biomes and to reduce the number of S. the species of big sizes are most particularly touched so that have it considers that the number of species which can die out in the years to come could be massive. The current extinction is named Extinction of Holocene the.

History of classification

Into occident, Aristote divided the world of alive between the animals and the Plante S. Its design, called Fixisme, is not very different from that of the scientists preceding it and will be taken again by the Christian theologists like Moslems, who by making a literal reading of the Bible, considered that the universe and the known world had been created in one week, and that it was not advisable to call this idea in question. The animals were there to serve the man. However starting from the Rebirth, certain ideas are called in question. Whereas work of Carl von Linné at the 18th century seeks with to classify all the alive species systematically in their giving a single and precise name ( binomial Nom ), Jean-Baptiste Lamarck, then especially Charles Darwin, works out theories of an evolution of the species. From these theories, and more particularly with that of Darwin will be born a controversy with the Créationniste S which often assert their support for a Christian biblical vision of the origin of life. The theory of Darwin is particularly décriée because it makes not only of the man an animal, but also the fruit of a evolution by selection process natural of which sexuality.

Linné had defined at the beginning three separate kingdoms themselves in the following groups: Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. This classification little by little will evolve/move with the wire of discovered in Zoologie or Paléontologie. This classification based on the anatomical characters and physiological tends to becoming a phylogenetic Classification, i.e. nearest possible to the genetic tree.

Protection of the animals

Many laws were adopted to protect the animals and their mediums from the action of the human . Some are more specific to the protection of the natural environments and others more specific to protect the animals from the ill will or silly thing of the human ones.

See also: List of international conventions relating to the protection of the animal, European Convention for the protection of the pets, animal Wellbeing

There exist also several types of organizations for animal protection, for example:

Economy

The animal is a source of revenue for the human ones. The uses of the animal go from food to transport, while passing by clothing. Since the Paleolithic , to make sure the presence of animals being able to render service to him, the man has domesticated a certain number of species and created of it breeding S. It knew, by selection of the crossings, to change the characteristics of certain species and has to create Hybride S so that the animals meet its needs more effectively. But it also uses them for its leisures by raising pet , by filming them, by discovering them within the framework of zoological gardens or safari S. These two last activities tend to become more respectful safeguard of the animals in their natural environment by supporting the reproduction of threatened species and the study for the parks. While trying to provide auxiliary incomes to the local populations, these last have consequently, more interests to preserve the animal life for the safaris. Certain human refuse the exploitation of the animals and refuse to eat meat, it is the Végétarisme. Others even refuse to consume the derivative products (egg, milk), it is the Végétalisme.

Symbolism

See also: Cryptozoologie, Thérianthropie

The men, since mists of time, lent to the animals virtues or characteristics either human, or divine. Thus certain animals became symbols, good number of Conte S are anthropomorphic and finally certain species of animals were also déifiées by certain people. The animals in the Univers of fiction are always very abundant.

References

External bonds

Qualitionnaire - legal and normative Definitions - Animal
Course within Organization of the Animal kingdom

Beats-smg: Gīvūnā Simple: Animal Zh-min-nan: Tōng-bu̍t Zh-yue: 動物

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