According to the theory of evolution, all the species of living beings on Earth gradually, many millions of years, evolved from their unicellular ancestors.More complex organisms is likely to have arisen from the colonies of protozoa.It can be traced if further explore the basic types of animals.The classification divides all creatures into species, families, orders, classes according to their structure and external characteristics that were acquired during the evolutionary improvement.
form new types of animal tissues, there were bodies that were not the ancient ancestors.The initial stage of this progress can be observed in sponges.Cnidarians have already expressed great endoderm and ectoderm, and 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 the evolution of the need to consider the details of their most important features.
Protozoa are microscopic creatures that have single-cell structure.Scientists know of about 15 thousand species of protozoa.The shape of their body different from radial to radiant asymmetry.Often form complex colonies that allows scientists to predict how any type of multicellular animals.They are divided into classes, depending on the methods of movement and body structure.
Sponges
most primitive multicellular organisms.They live mostly in the ocean.They are divided into three classes, depending on the composition of the skeleton.Lifestyle them attached.Other types of the animal kingdom they opposed because sponges are no specific organs and tissues.There is an external, protects the body from the surface, and an inner layer composed of a special for collar flagellated cells.Between them is mesoglea - sometimes quite massive group of cells, a part of which forms the skeleton.
Coelenterates
The bodies of these animals are composed of only two layers of cells that surround the body cavity, called intestinal, with one mouth opening.Possess the rudiments of the nervous and muscular tissue.Circulatory and excretory system does not.Lifestyle coelenterates is sedentary or svobodnopodvizhnym.Live, with few exceptions, in seawater and form vast colonies.This type includes jellyfish, corals and sea anemones hydroid polyps.
Flatworms
Ploskotelye creatures that have the beginnings of the excretory system and brain.Anus still missing.Representatives of this type - hermaphrodites.To this type belong Turbellaria or turbellarians and some parasites - lentochniki and flukes.
Roundworms
Have the mouth and anus joined intestine.The core group - nematodes, many of whom are parasites, but there are free-living species.This blind branch of evolution, further impact on the development of organisms, this group did not have.This type includes more hair-worm, rotifers and parasites, which are often treated as separate groups.
Annelida
The bodies of these animals are composed of individual segments.Enjoy the circulatory system, a high ability to regenerate limbs and primitive beginnings of the secondary body cavity.Other, more highly developed types of the animal kingdom have been formed under the influence of these changes.From marine annelid worms there were numerous representatives of the group of arthropods.
Shellfish
Animals, soft body which is usually protected by the sink.Have highly developed nervous system, the secondary body cavity.There the senses and the heart - a muscle that pumps blood.In bivalves can distinguish the trunk and leg in gastropod - head.They live in both salt and fresh water and on land.
Echinoderms
inhabitants of the deep sea.Dimensions of the largest representatives do not exceed 50 cm. Type of classes includes sea urchins, stars, roses and others.Lifestyle motionless, so developed a unique to echinoderms five-way symmetry.The representatives of the types of circulatory system mezodermichesky internal skeleton.
Arthropods
types of animals are very extensive.It is this group are arthropods.This type - the most diverse and rich in species.Characteristic features are the presence of the type of complex sensory organs in the form of isolated appendages mouth - scape, a clear division of the body into sections, limb, consisting of segments for more efficient movement.Development held by arthropods trilobites extinct, primitive group, which is the parent for the crustaceans and arachnids, to the highest flying insects.Millipedes are considered to be a transitional link the evolution of this type.
chordal
type includes types and classes, different in appearance, lifestyle, environment.The types of the nervous system in animals united formed on the dorsal part of the body tube, is the center of all the many endings, which protects the notochord, cartilage or bone rod support skeleton.Development of the representatives of the various classes can be tracked by lichinkohordovyh and bescherepnyh (Amphioxus) to highly primates, highly intelligent.
Fish
There cartilage, or lopasteperye myasistolopastnye, bone.Representatives of the first group have a thick skin placoid peculiar to their scales.The mouth is located on the lower side of the body, there is no easy and swim bladder skeleton consists of cartilage.
Lopasteperyh fish are divided into lungfish and Crossopterygii.The latter are represented today by only one genus, living in the Indian Ocean.They are very similar to the ancestors of amphibians, and are of particular interest of researchers in the theory of evolution.Lungfish have both gills and lungs.
Bone - is a big part of the modern representatives of the fish class.Have a swim bladder and the solid skeleton;Skin is mostly covered with scales, but there are numerous exceptions.
Amphibians
Usually, the larvae of these creatures breathe with gills and live in the water.The adult is light and live on land.The skin moisturized and devoid of hair or scales.This class includes frogs, newts, toads, salamanders.
Reptiles
body is covered with scales, and live on land and in water.In ancient times, this class has dominated among the rest of the number, but after the main place was occupied by mammals.They have a variety of sizes, body shape, lifestyle.Crocodiles, lizards, snakes, turtles are members of reptiles.
Birds
anatomically similar to reptiles, but they had the ability to independently maintain their body temperature regardless of environmental conditions.Birds perfectly formed light, four-chambered heart and wings, which enable most of them to move through the air.
Mammals
so named because of the presence of special glands, the secret of which they feed their young.The body usually covered with hair, they are warm-blooded, limbs subsumed under body and deployed forward.In higher mammals, primates, develop intelligence, which is very conducive to survival.
types of animal nutrition
All beings are divided into 3 categories according to the method of supply:
• Herbivores .Drink only vegetarian food - algae, grass, leaves or fruit.For example, elk, deer, rabbit.
• Predators .They eat insects, or the flesh of other animals.For example, a frog, tiger, lynx.
• Omnivore .Depending on the environmental conditions, can eat both plant and animal food.For example, bear, bird, wild boar.
Ocean Life
ancient ancestors of the creatures is gradually emerging from the ocean, which became the cradle of life of the Earth.This migration could occur in several ways - through the coast of the land, in fresh water or in underground caves.Due to the radical changes of habitat changed and improved types of animal tissues, it was necessary for survival.Some groups - whales, reptiles and birds - and then returned to the sea after a long evolutionary path.
Now representatives of most classes are found in the ocean or beside him.Very many species of animals, especially invertebrates, remain unchanged for millions of years and are a valuable resource for learning.Other major types of animals are considered to be relatively young, but the study helped identify genetic links between seemingly different groups.This has a huge impact on the awareness of the unity of man with nature and understanding of the enormous similarity of living creatures.
