Type of arthropods: general characteristics, classification

Our planet is very replete with various creatures, many diverse animals and plants we have. But in this paper we will analyze in detail the type of arthropods. A general description of these living things will also be presented in the article.

number

This is the largest and richest type in the animal kingdom. Representatives there are about a million species. Their number is one third of all living organisms on our planet, both living at this time and extinct. Before we examine the question "General characteristics of the type of arthropods" (the 7th grade of a comprehensive school is obliged to introduce children to its representatives), it is necessary to know that a large number of creatures still remain unexplored, their actual number can theoretically reach ten or more millions.

They are common everywhere: in the seas, oceans, freshwater springs, on land. Based on which ecosystem a particular species has chosen, evolution and nutritional preferences can be judged. The type of arthropods, the general characteristic of which is our main task, is diverse, we suggest considering classification for systematization.

Protection

We have already mentioned that the type has a large number of creatures, but despite this variety, they all have a relatively similar body structure. Considering the type of arthropods (general characteristic), we note a similar feature - an external rigid skeleton consisting of chitin. Some species have an exoskeleton containing lipids, proteins, and calcium carbonate. This outdoor suit provides them with body protection and support. The walls of the carapace also strengthen the muscles.

It is also important that all representatives are exposed to molting, this process occurs due to the fact that the exoskeleton does not grow, and a larger house is needed during the growth of the animal.

Body

The arthropod type is rich and diverse. A common characteristic also includes such a feature as segmentation. The whole body is divided into segments. Sometimes they grow together, in which case they are called tagmata, and the process is tagmasis. One example is the fused head, chest and abdomen. Arthropods also have processes with joints - that’s where the name comes from, literally translated as “jointed legs”.

Take the earliest and most primitive arthropods, then each segment of their body was associated with only one pair of appendages. However, most species have evolved, and the limbs have changed, other structures have formed, for example:

• oral apparatus;
• antennae;
• reproductive organs and so on.

Arthropods can have either branched or non-branching appendages.

Feelings, gas exchange, blood circulation

Many representatives have well-developed sensory organs (paired faceted eyes), although some do not have this privilege. Their circulatory system is open, has no blood vessels.

Gas exchange occurs in several ways:

• gills;
• trachea;
• lungs.

Most arthropods are dioecious, usually fertilization occurs internally, and eggs are laid.

Type of arthropods: general characteristics, classification

These are symmetrical animals. It is important to mention that they originate from annelids. If you analyze it well, you can notice the similarities in the structure. The only thing in the course of development and evolution, the former have reached a high level of organization. Arthropods (general characteristics of the type, systematics and other questions will be thoroughly dedicated) are divided into the following main classes:

• crustaceans;
• arachnids;
• insects.

In turn, each class is divided into units. For example, among crustaceans distinguish: cladocera, copepods and decapods. Arachnids include: spiders, ticks and scorpions. And insects have a very large number of orders, such as:

• orthoptera;
• dragonflies;
• dipterous;
• coleoptera;
• half-winged;
• hymenoptera;
• winged;
• fleas and many others.

Let's consider each class separately.

Crustaceans

This is a fairly diverse class, numbering about forty thousand species. Basically, they can be found in the seas and freshwater reservoirs, but there are some who have mastered the land.

Although the type of arthropods (the crustacean class, the general characteristics of which are considered in this section) is very rich, a number of similar features can be distinguished, for this we will give a table at the end of the paragraph that helps to systematize the knowledge gained.

They lead a floating, crawling or attached lifestyle. Among them, parasites are even found. As mentioned earlier, arthropods differ in body segmentation; there are ten to fifty of them in this class.

Briefly consider the characteristic of a typical representative of this class, all known crayfish. From the name it is already clear that he lives in fresh water. Its role in nature and for man is very great. Note that it is possible to distinguish even outwardly male and female.

Activity is achieved at night, he eats exclusively plant foods, eating both live and dead prey. The size of a mature individual is from fifteen centimeters or more, they molt once a year, in young animals this process is observed several times a year.

Like other representatives of arthropods, the circulatory system is not open, the heart looks like a five-sided sac and is attached to the back wall of the body. It is also important to know that the head and body are connected. Tactile and olfactory feelings are sharp due to a long mustache. The eyes are complex and attached to the flagella, which compensates for the immobility of the head.

Arthropod type, arachnid class: general characteristic

Like the previous one, it is very rich, has more than thirty thousand species of living creatures, most of which live on land, but there are also representatives of secondary water. Like crustaceans, they have a cephalothorax, in addition to this there is an abdomen. Note that segmentation is subject to change (some ticks do not have a segmented body at all, such as a canine).

The first segment of the body (cephalothorax) attaches six pairs of limbs to itself:

• Two pairs - the jaw.
• Four pairs - tentacles.

There are no limbs on the abdomen, but some representatives of this class retained pulmonary sacs, genital plates, or spider warts.

Another distinguishing feature of arachnids is the outer layer, consisting of lipoprotein, which protects the body from moisture loss. Most have poisonous and spider glands. As a rule, arachnids are predators, but a large group are parasites and herbivores. Breathing is carried out using the lung sacs or trachea, but in spiders using these two organs. The organs of vision, touch, smell and taste are quite well developed, but for some ticks, vision is completely absent.

Fertilization occurs internally, with live births observed in some species of ticks and scorpions. Although this class is quite diverse, such units as:

• Spiders.
• Ticks
• Scorpions.

Insects

Here is a table reflecting the main features of insects.

This is the least studied class, but no less significant compared to the rest, it is poorly studied by science only because it is young.