Evolution of animals is a process of their consecutive and continuous historical development. Driving force of evolution is natural selection – survival of the most adapted types.
Instruction
1. According to abiogenous hypotheses of origin of life on Earth, synthesis of organic biopolymers became the first step on the way of origin live on the planet. By chemical evolution, biopolymers passed to the first living organisms which developed further already by the principles of biological evolution. During this historical development and complication the set of life forms appeared.
2. The history of Earth is subdivided into long periods of time – an era: Hadean, Archean, Proterozoic, Paleozoic, Mesozoic and Cenozoic. The paleontology – science about ancient organisms of last geological eras helps to obtain data on development live on Earth the scientist. On fossils – sinks of mollusks, teeth and scales of fishes, a shell of eggs, skeletons and other firm parts – the organisms living on the planet dozens, hundreds millions years ago are studied.
3. It is considered that during an archaean ("most ancient") era on the planet bacteria which result of activity was a marble, graphite, limestone, etc. dominated. Also the remains of the cyanobacteria capable to oxygen-free photosynthesis are found in deposits of the Archean. At the end of the most ancient era the living organisms, under the assumptions, were divided on prokariot and eukariot.
4. In the Proterozoic – an era of early life – living organisms continued to become complicated, and their ways of food and a reproduction – to be improved. All life was concentrated in the water environment and on coast of reservoirs. Among animals a big variety of coelenterates and sponges appeared. Towards the end of a Proterozoic era there were all types of invertebrate animals and the first chordates – acranial. Find in deposits also the remains of worms, mollusks and arthropods. The only descendant of an era of early life who remained still consider a lancelet.
5. The Paleozoic is an era of "ancient life". In it allocate the cambrian, ordovician, Silurian, Devonian, coal and Perm periods. At the beginning of the Paleozoic, the Cambrian, there were invertebrate animals covered with the firm skeleton constructed of chitin, a carbonate and phosphate of calcium, silicon dioxide. The fauna was mainly presented by ground organisms – coral polyps, sponges, worms, arkhetsiata, erinaceouses and arthropods. Trilobita – the most ancient arthropods – reached the greatest blossoming.
6. The Ordovician is characterized by the strongest flooding of Earth and emergence of a set of swamps. During this period arthropods and cephalopod mollusks became especially popular, but also the first beschelyustny vertebrata appeared.
7. In a silura the animals and plants came out of the water. And the myriapods who came, apparently, from trilobitoobrazny became the first land animals arachnoid. In the Devonian Period there were primitive chelyustnoroty fishes having a cartilaginous skeleton and covered with an armor. From them there were sharks and kistepery fishes, and from the kistepery fishes capable already to breathe atmospheric air, – the first amphibians (ikhtiosteg, stegotsefala).
8. In the Carboniferous Period, the period of swamps and extensive marsh forests, Amphibia reached blossoming and the first insects – cockroaches, dragonflies, coleoptera appeared. There were also primitive reptiles occupying drier places. In Perm there was a climate to the land more cool that led to extinction of trilobit, large mollusks, large fishes, large insects and arachnoid. Reptiles became the most numerous at this time. There were ancestors of mammals – a terapsida.
9. In the Mesozoic distinguish the Triassic, Jurassic and cretaceous periods. In the Triassic there was a set of reptiles (turtles, ichthyosauruses, crocodiles, dinosaurs, plesiosauri) and insects. At the end of the period the first representatives of warm-blooded appeared. In the Jurassic Period dinosaurs reached development peak, the first birds similar to reptiles appeared.
10. In the Cretaceous there were marsupials and placentary mammals. At the end of chalk there was a mass extinction of many animal species – dinosaurs, large presmyskayushchikhsya, etc. Scientists connect it with climate change and the general cold snap. Advantages in fight for survival were got by warm-blooded animals – birds and mammals which blossoming fell on the Cenozoic – the era of new life consisting of the periods of the Paleogene, Neogene and anthropogene.