Review of Basic Biological Knowledge in Junior Middle School-Summary of Classification of Knowledge Points 1At present, there are about 1.5 million known animals. These animals can be divided into two categories: one is vertebrates, which have spines in their bodies; the other is invertebrates, which have no spines in their bodies. 2. Biodiversity: 1) diversity of species; 2) diversity of living environment; 3) diversity of sports. 3. The reason why fish can live in water is that two characteristics are essential: 1) they can get food and defend against enemies by swimming; 2) they can breathe in water. 4. Fish can overcome resistance in water: streamlined (shuttle-shaped) body; body surface secretes mucus. 5. When fish swim, they are driven by the left and right swings of the tail on the trunk. They are balanced by the dorsal fin, pectoral fin, pelvic fin and buttock fin, and keep the forward direction by the caudal fin. 6. When it is difficult to do experiments directly with the object of study, sometimes we use models to do experiments, that is, to imitate the object of experiment to make models, or to imitate some conditions of experiments, such experiments are called simulation experiments.7. Fins play an assistant and coordinated role in motion.8. Gill is the respiratory organ of fish. 9. The gills are rich in capillaries, so the gills are bright red. 10. Gill filaments are numerous and thin in order to expand the contact area with water and facilitate gas exchange.Gill is not easy to absorb oxygen in the air. When fish leave the water, gill filaments cover each other, which reduces the area of contact with the air. They can not get enough oxygen from the air, so they die of anoxia.11. The gills of fish are very important for breathing in water: the gills are bright red and rich in capillaries; the gills are many and thin.12. Water flows in from the mouth of the fish and out from the posterior edge of the gill cover. 13. Oxygen decreases and carbon dioxide increases in the water flowing out of gills. 14. Gas Exchange: O 2 in Water - Co 2 in Gill Filament in Capillary of Gill Filament 15. The main characteristics of fish: the body surface is often scaly, breathing with the gill, swimming through the tail swing and the coordinated role of fins. 16The food enters the digestive cavity from the mouth, and the food residue after digestion is still discharged from the mouth. These animals are called coelenterates. 17Animals whose body is soft and protected by shells are called mollusks. 18. Animals with hard armor on their surface are called crustaceans.Crustaceans breathe with gills.19. The coelenterates, mollusks and crustaceans are invertebrates. 20. All kinds of organisms in water are important components of aquatic ecosystem. They form a close and complex relationship through food chain and food web. At the same time, they are affected by the aquatic environment. The change of species and the growth and decline of quantity will affect human life. 21. Compared with the water environment, the terrestrial environment is much more complex.1) relatively dry; 2) large temperature difference between day and night; (3) lack of buoyancy in water; (4) gaseous oxygen; (5) complex and changeable terrestrial environment. 22. The adaptation of animals living on land to the environment: 1) generally have a structure to prevent water loss; 2) not subject to the buoyancy of water, they generally have organs to support the body and movement, which are used for crawling, walking, jumping, running, climbing and other sports to find food and avoid enemies; 3) generally have various respiratory organs that can breathe in the air and locate inside the body, such asTrachea and lungs; 4) Generally developed sensory organs and nervous system, able to respond to the changing environment in a timely manner. 23. Linkages are not mollusks. Linkages are invertebrates. 24. Animals whose bodies are composed of many similar annular segments are called annelids. 25. Earthworms live in moist soil rich in humus, because earthworms are cold-blooded animals, temperature changes little, suitable for earthworms. 26. Segmentation can make the body of earthworms move flexibly. 27. Earthworms move by contraction and relaxation of muscles, support and fixation of bristles. 28. Earthworms have no special respiratory system. Earthworms breathe by

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