The main types of animals. Types of animals: classification

According to the theory of evolution, all kinds of living beings on the Earth gradually, long millions of years, developed from their unicellular ancestors. More complex organisms, most likely, arose from colonies of protozoa. This can be traced if we study in more detail the main types of animals. Classification divides all creatures into species, families, orders, classes according to their structure and external characteristics, which were acquired during evolutionary improvement.

New types of animal tissues were formed, organs appeared that were not found in the most ancient ancestors. The initial stage of such progress can be observed at the sponges. The coelenterates already have well expressed endoderm and ectoderm as well as the rudiments of the musculature. Higher types of animals are characterized by a complex structure of the nervous system and other organ systems. To understand evolution, it is necessary to consider in more detail their most important features.

Protozoa

These are microscopic creatures that have a unicellular structure. Scientists know about 15 thousand species of protozoa. The shape of their body is different, from radial-radial to asymmetric. Often form complex colonies, which allows scientists to assume how multicellular types of animals have arisen. They are subdivided into classes, depending on the modes of movement and body structure.

Sponges

The most primitive multicellular organisms. They dwell most often in the sea. They are divided into 3 classes, depending on the composition of the skeleton. They have a way of life attached. Other types of Animal Kingdom are opposed to them, because sponges lack characteristic organs and tissues. There is an external, protecting the body from the surface, and an inner layer consisting of special flagellar collar cells. Between them is a mesogloe - sometimes a very massive group of cells, some of which form a skeleton.

Coelenterates

The bodies of these animals consist of only two layers of cells that surround the body cavity, called the intestinal, with one mouth opening. They have rudiments of nervous and muscle tissue. There is no blood and excretory system . Lifestyle in coelenterates can be sedentary or free-moving. They live, with rare exceptions, in sea water and form extensive colonies. This type includes jellyfish, corals, hydroids and actinia.

Flat worms

Plane creatures that have rudiments of excretory system and brain. There is still no anal opening. Representatives of this type are hermaphrodites. This type includes ciliated worms, or turbellarians, as well as some parasites - ribbons and flukes.

Roundworms

They have oral and anal openings connected by the intestine. The main group is nematodes, among which there are many parasites, but there are also free-living species. This blind branch of evolution, this group did not exert further influence on the development of organisms. This type is also referred to as hairy, rotifers and Acanthocephala, which are often treated as separate groups.

Ringworms

The bodies of such animals consist of separate segments. They have a circulatory system, a high ability to regenerate with the rudiments of primitive limbs and the secondary body cavity. Other, more highly developed types of Animal Kingdom were formed under the influence of these changes. Numerous representatives of a group of arthropods have originated from marine annelids.

Shellfish

Animals whose soft body is usually protected by a shell. They have a highly developed nervous system, a secondary body cavity. There were sensory organs and the heart - a muscle that pumps blood. In bivalve mollusks, one can distinguish between the trunk and the leg, and in the gastropods - the head. They live in marine and fresh water, and on land.

Echinoderms

Inhabitants of the sea depths. The sizes of the largest representatives do not exceed 50 cm. The type includes classes of sea urchins, stars, lilies and others. The way of life is immovable, due to which the five-beam symmetry peculiar only to the echinoderm was developed. Type representatives have a circulatory system, a mesodermic internal skeleton.

Arthropods

The types of animals are very extensive. It is this group that the Arthropods are. This type is the most diverse and rich in species. Characteristic features of the type are the presence of complex sensory organs in the form of isolated appendages of the oral cavity - antennae, a clear division of the body into divisions, limbs consisting of segments, for more efficient movement. The development of arthropods was from extinct trilobites, a primitive group that is ancestral to crustaceans and arachnids, to higher flying insects. Millipedes are considered a transitional link in this type of evolution.

Chord

Type includes species and classes, diverse in appearance, way of life, habitat. Types of the nervous system in animals are united by a tube formed on the dorsal part of the body, which is the center of all the numerous endings, which is protected by a chord, a cartilaginous or bony rod, and a skeleton support. The development of representatives of various classes can be traced from larva-chord and non-cranial (lancelets) to complexly organized primates, characterized by high intelligence.

Fish

There are cartilaginous, loposterous or flesh-bones, and bone. Representatives of the first group have dense skin with a placoid, which is characteristic only of scales. The mouth is located on the lower side of the body, there are no lungs and a swimming bladder, the skeleton consists of cartilages.

Lopasteper fish are divided into lung and lung cysts. The latter are now represented by only one genus living in the Indian Ocean. They are very similar to the ancestors of amphibians and are of particular interest to researchers who advocate the theory of evolution. Larcum-lungs have both gills and lungs.

Bony - this is a large part of the modern representatives of the fish class. They have a swim bladder and a solid skeleton; The skin is mostly covered with scales, but there are numerous exceptions.

Amphibians

As a rule, the larvae of these creatures breathe gills and live in water. The adult has lungs and lives on land. The skin is moisturized and devoid of hair or scales. This class includes frogs, newts, toads, salamanders.

Reptiles

The body is covered with scales, live both on land and in water. In ancient times this class dominated among the rest in numbers, but after the main place was occupied by mammals. They have a variety of sizes, body shape, lifestyle. Crocodiles, lizards, snakes, turtles are representatives of reptiles.

Birds

Anatomically close to reptiles, but they have the ability to independently maintain the temperature of their bodies, regardless of the conditions of the environment. Birds have perfectly formed lungs, a four-chambered heart and wings, which allow most of them to travel through the air.

Mammals

They are called so because of the presence of special glands, the secret of which they feed the cubs. The body is usually covered with hair, they are warm-blooded, limbs are brought under the body and deployed forward. In higher mammals, primates, intelligence develops, which is very conducive to survival.

Types of food animals

All creatures are divided into 3 categories according to the mode of nutrition:

• Herbivores . Eat only vegetative food - seaweed, herbs, leaves or fruits. For example, elk, deer, rabbit.

• Predators . Eat insects or the flesh of other animals. For example, a frog, a tiger, a lynx.

• Omnivore . Depending on the surrounding conditions, they can eat both plant and animal food. For example, a bear, a tit, a wild boar.

Ocean of Life

The ancient ancestors of modern beings gradually emerged from the ocean, which became the cradle of the life of the Earth. This migration could take place in several ways - across the coast to land, into fresh water or into underground caves. In connection with the cardinal change in the habitat, the types of animal tissues that were needed for survival changed and improved. Some groups - whales, reptiles and birds - then returned to the sea after a long evolutionary path.

Now representatives of most classes live in the ocean or next to it. Very many animal species, especially invertebrates, remain unchanged for millions of years and constitute a valuable resource for learning. Other main types of animals are considered relatively young, but their study helped to identify genetic links between seemingly different groups. This has a tremendous impact on the realization of the unity of man with the surrounding nature and the understanding of the great similarity of living beings.