Snakes are friends of human beings and indispensable animals in the ecological environment. There are many kinds of snakes. There are about 3000 species in the world, and poisonous snakes account for about 1/6. There are 160 kinds of snakes in China, 47 of which are poisonous snakes. Through the study of snake knowledge, children can understand the morphological structure, living habits, the difference between poisonous snakes and non-poisonous snakes, and the role of snakes in the ecological environment, thus arousing people's awareness of environmental protection.
First, the morphological structure of the snake
Snakes walk in various ways, either straight or tortuous, which is determined by the structure of snakes. The snake is divided into three parts: body, trunk and tail. The neck is between the head and trunk, and the boundary is not obvious. The trunk and tail are bounded by anus. Snakes have no limbs and are covered with scales, which can protect the skin. Snakes are divided into poisonous snakes and non-poisonous snakes. The head of a non-venomous snake is generally conical, with a thin front end and a thick back end. There are poisonous snakes that are triangular; The snake's trunk is very long and cylindrical; The tail of a snake is the part behind the anus.
The internal structure of snake is divided into ten parts: skin system, skeleton system, muscle system, respiratory system, digestive system, reproductive system, nervous system, sensory organs and chromosomes.
How can a snake climb without feet In fact, snakes can not only climb, but also climb quite fast.
The snake can crawl because it has a special way of movement: one is bending movement, and all snakes can crawl forward in this way. When crawling, the snake bends horizontally on the ground, making the bent back exert force on the rough ground, and the snake is pushed forward by the reaction of the ground. If the snake is placed on a smooth glass plate, it will not be able to crawl in this way. Of course, there is no need to worry about snakes, because there is no ground as smooth as glass in nature. The second is crawler movement. Snakes have no sternum, and their ribs can move freely back and forth, and there are costal muscles connected between the ribs and the abdominal scales. When the costal muscles contract, the ribs move forward, driving the broad abdominal scales to stand up in turn, that is, slightly inclined. The inclined belly scales are like stepping on the ground, but at this time only the belly scales are moving and the snake body is not moving. Then the costal muscles relax, and the rear edge of the abdominal scales exerts force on the rough ground, and pushes the snake forward by reaction. The effect of this action is to make the snake's body crawl straight forward, just like a tank. The third way is telescopic movement. Lift the front of the snake and stretch as far as possible. When it touches the supported object, the snake's back will shrink forward, then the front of the snake body will be lifted and stretched forward to be supported, and the back will shrink forward again, so that the snake can keep crawling forward. Snakes that crawl slowly on the ground, such as lead-colored water snakes, will expand and contract rapidly when disturbed, speeding up the crawling speed and giving people the feeling of jumping.
Second, the living habits of snakes
Snakes belong to reptiles and snakes, and they are real terrestrial vertebrates. There are poisonous snakes, but as long as you pay attention, it's not that dangerous. Snakes mainly eat mice (frogs, birds, etc. ). Snakes are ugly, with strange shapes and colors, covered with scales, high head and neck, swinging tail, moving fast, courting and swimming, which is really hard to please. Snakes like to live in cool, humid, inaccessible, overgrown with weeds, lush trees, wooden tree holes or piles of rocks, woodpiles, haystacks, ancient ridges, and places rich in bait. These are the places where they live, haunt and breed. Some snakes live in water.
They like to live in grave caves, and thick granular feces can be seen at the entrance, so that we can know whether there are snakes in the caves. Snakes have the habit of hibernating. When they sleep in caves in winter, they sleep for months. They don't eat or drink, and they don't move. When spring blooms, the snake wakes up and begins to go out for food, taking off its original coat. The weight and even the name of a snake can be measured from the diameter and length of its shed fur. Shortly after the snake molts, its activity and foraging amount increase, and its physical condition gradually recovers. As the temperature rises gradually, it enters estrus from late April to mid-May. When looking for a mate, the chirping of male and female snakes is crisp and bright, and "dadada" seems to hit a stone.
The spawning period of snakes is generally from late April to mid-June, which varies from species to species. The laid snake eggs are generally bonded into a large egg mass, and the number of eggs in the egg mass varies from 8 to 15. Snakes are often hungry or semi-hungry. Generally, they prey by "waiting for the rabbit", but sometimes they will take the initiative to attack. The author once witnessed a bamboo snake chasing a frog by the river. Frogs jump into the river, and snakes jump into the river, just like two divers in tandem. I've also seen snakes prey on birds' eggs. It crept up the wall near the eaves, swam to the swallow's nest and kept sticking out its tongue, scaring away the parent birds. When the snake finds its eggs, it attacks and entangles them first, and then opens its mouth to swallow them when it is safe. Don't think its mouth is small. In fact, it can swallow food 8- 10 times larger than its head. After eating enough food, the snake feels very tired and enters a rest state, which is easy to be caught. As for the frequency of feeding snakes, it varies with the variety and size of snakes. Generally, the peak of foraging activities in summer, especially the spawning and breeding period, is once a day or once every other day. If the snake is a little bigger, it is usually eaten once every 3 days to once a week because of its great foraging ability. Snakes also like to bask in the sun, usually around 10- 12 in the morning. When sunbathing, people usually lie on the grass on the ground or wrap or lie on the trunk, and some are half naked outside the hole and curled up outside the stone pile in various postures. The law of snake activity is mostly during the day and comes out at night, which varies from species to species.
Third, there is a difference between poisonous snakes and non-poisonous snakes.
How to distinguish poisonous snakes from non-poisonous snakes? It is not comprehensive enough for ordinary people to distinguish whether the head is triangular or whether the tail is thick or short or whether the color is bright. Although the head of poisonous snakes is obviously triangular, there are also some poisonous snakes whose heads are not triangular; A pseudo-venomous snake with a triangular head. The tails of viper, viper and cobra are really thick, but the tail of welding head is slender; Many brightly colored snakes, such as the Jade Spotted Snake and the Red Chain Snake, are not poisonous snakes, while the color of the Agkistrodon is like mud or shit, which is ugly but poisonous. So the difference between poisonous snakes and non-poisonous snakes is mainly based on the following points:
1, poisonous snakes with poisonous glands, poisonous snakes without poisonous glands. Poisonous glands evolved from salivary glands. Located on both sides of the head and behind the eyes, it is enclosed in the muscles of the jaw and can secrete venom. When a poisonous snake bites something, the muscles around the poisonous glands contract, and the venom is injected into the bitten body through the venom tube and the fangs' tubes or grooves, so that it is poisoned. No poisonous snake has this function.
2. Venom tube is a pipeline for transporting venom, which is connected between poison glands and fangs. Only poisonous snakes are poisonous tubes.
3. The poisonous snake has fangs, which are located in front of or behind the nontoxic teeth of the maxilla and are longer and larger than the nontoxic teeth.
So, which non-poisonous snakes are easily confused with poisonous snakes?
Several kinds of non-poisonous snakes are often mistaken for poisonous snakes. Because of their special appearance, bright spots and fierce temperament, they are often regarded as poisonous snakes by some locals. In fact, this kind of snake is harmless to human body when it bites people. Such as tiger-spotted snake (also known as pheasant-Bozi snake) and red chain snake (also known as red chain).
Non-toxic yellow chain snake (also called Huang Chi chain) is easily confused with poisonous snake in appearance or color spots, and is often mistaken for golden ring snake because of black and yellow stripes on its back; Lycodon ruhstrati with black back, because of the black and white stripes on the snake's back, is also easily mistaken for a silver ring snake; The neck-edge snake (also called pseudo-viper) has a thick body, a short tail, a brown back, two rows of thick dark brown patches, and a slightly triangular head, which is very similar in appearance to viper or viper. Green snake (also called green bamboo label) is often confused with bamboo leaf green because it is green all over.
Fourth, the role of snakes in the ecological environment
We know that wild animals play an extremely important role in maintaining the natural ecological environment. Wild animal species are all important links in the ecosystem, and they are interdependent and mutually restricted through the food chain. Once a link in the food chain goes wrong, the balance of the whole ecosystem will be seriously affected. Grass-grasshopper-frog (mouse)-snake-eagle is a kind of food chain. If humans hunt snakes in the wild without restraint, there will be fewer and fewer snakes, which will lead to more and more rampant rodents in forests, grasslands and farmland. The losses caused by rodents and pests to agriculture, forestry and animal husbandry are immeasurable, and the ecological environment will be seriously damaged.
Conclusion: Snakes are our friends. We should protect snakes, especially some rare snakes, and don't kill them in large quantities, otherwise it will destroy the ecological balance. As the future of the motherland, we have the responsibility to stand up and maintain the ecological balance.