After the children drank water one after another, everyone's noise slowly subsided, Bei Bei clapped his hands at the right time and said with a smile: "Students, everyone did a great job today, are you tired?" ”

"Tired !!" The 54 students of the 19th class of Yangfan Primary School naively shouted in unison.

"Teacher, my hands are blistered." The little girl Roman stood up and said squeamishly.

"Teacher, my shoulder hurts." The little boy Zhang Xiaoyu stood up with his shoulders and reported.

"Hehe, you've worked hard, let the teacher see." Bei Bei was about to stand up, Lei Ping had already rushed to the front with an emergency medicine box, turned around and said, "I'll deal with it, Teacher Yang, take a rest." ”

Bei Bei smiled and nodded her head and sat down again, she didn't notice that Zhang Lu and Kong Wenjia were also sitting behind her not far from her, looking at her quietly.

Bei Bei glanced at the students again, and everyone was sitting upright, so she looked up at the sky and felt that it was time to show the theme of today's project to the children. At this time, Bei Bei suddenly remembered that she had an appointment with Zhang Lu at night, and she estimated that Zhang Lu should almost return to Changshan.

"Okay, students, now I want to ask you a question." Bei Bei took a sip of water, then closed the lid, shook the bottle in his hand and said to his classmates.

"We worked all afternoon today, and it made us feel tired, because we used up a lot of energy, right?"

"Yes." The children shouted in unison.

"So, do you know where our physical strength comes from?" Bei Bei then asked.

The children were suddenly silent, and suddenly Zhang Xiaoyu, who was being treated by Teacher Lei, said: "Teacher, I think physical fitness comes from the food we eat. ”

Bei Bei's eyes lit up when he heard Zhang Xiaoyu's answer, and then he smiled: "That's right, Zhang Xiaoyu is awesome." ”

When the other children heard the teacher praise Zhang Xiaoyu, some looked at him enviously, some showed unconvinced expressions, and some were still thinking about other answers.

Bei Bei was like a big child at this time, and she continued to say in a lively voice: "We humans have had the instinct to eat milk since newborn babies, which means that eating is the most important subject that accompanies human beings throughout their lives, and we need to consume enough food and water every day in order to get energy so that we can survive, right?" ”

"Yes!" The students replied.

"So, why do we get energy?" Bei Bei asked.

Li Zitong, the youngest in the class, stood up: "I think it's because human beings need energy to work, so that we can build our home on earth and make her more beautiful." ”

Bei Bei smiled and nodded at her: "Well, this classmate is right. We humans need to eat reasonably, replenish water, and obtain energy from food every day, which we collectively call bioenergy. Human beings not only need energy for labor, but in fact all human activities need to consume energy, such as walking, talking, studying, thinking, smiling, driving, holding hands with others, as well as all kinds of sports and work labor, and even missing a person, blinking eyes, and breathing all need to consume energy. ”

"So, we have to eat regularly every day so that we can replenish enough energy so that we can survive, do you understand?"

The children were listening attentively to Teacher Beibei's vivid speech, and everyone nodded honestly at the same time, expecting the teacher to continue speaking.

Although Zhang Lu and Kong Wenjia behind Bei Bei couldn't see Bei Bei's expression, they were infected by Bei Bei's emotional and subdued speech, and they looked at each other and smiled at each other, and also looked forward to Bei Bei continuing her next speech.

"In addition to satisfying the needs of various human activities, the purpose of human energy replenishment is also an important task, that is, to supply nutrients so that human beings can grow. Therefore, from an infant to an adult, human beings need to supplement enough balanced nutrition from food every day, which is very important at this stage of human beings from infancy to adulthood. So students, you have to eat on time every day, and you must not be picky eaters, so that you can grow up healthily, you know? ”

"Got it." The childish voices of the children are interspersed with absolute obedience.

"In fact, not only us human beings, but all living creatures on the earth we live in, whether plants or animals, must absorb energy from the outside world according to certain laws. As long as this life exists, then its process of obtaining energy from the outside world will not stop. Therefore, the prerequisite for the continuation of life is whether it has the ability to obtain energy, and once the life ends, then it means that it has stopped exchanging energy with the outside world. ”

"The reason why all the flowers and trees on the earth, we humans and all other animals can thrive here is because they are constantly replacing their energy with the outside world. In this sense, the essence of life is actually the embodiment of a unique and complex transformation of energy. Therefore, the students remembered that one of the most fundamental prerequisites for people to live is to eat on time every day. Similarly, all other animals and plants must be fed regularly in order to keep them alive. ”

Bei Bei found that her language was a bit abstract for children, so she ended with a layman's sentence.

"Teacher, do plants have to eat too?" Wang Yating, who sat in the last row, asked.

"Well, that's right, plants also need to eat, and most plants get not only water and nutrients from the soil, but also energy from sunlight, which can be understood as eating. It's just that the main way we humans get our energy is by eating, so we might think it's strange how other creatures eat, you know? Bei Bei patiently explained.

Wang Yating nodded when she heard this, and the other children could also understand Beibei's words, and everyone looked at the teacher, serious and curious.

Looking at the serious appearance of the children, Bei Bei continued with satisfaction: "So, all life on the earth is a carrier of energy transfer, they constantly obtain energy from the outside world, and then release the energy in various ways, which is the way life reflects its value. It is conceivable that if there is no energy from the outside world for the life on Earth to consume, then they will die. ”

"In fact, all matter in the universe is a carrier of energy, not only living beings are carriers of energy, but living organisms as a very complex energy management system, can survive in the ordinary environment of the earth, and release energy much faster than other inanimate carriers such as stones, iron ore and other substances. However, an important difference between living things and inanimate matter is that living things can not only release energy, they can also absorb energy from the outside world on their own and repeat the cycle, while inanimate matter can only passively absorb a little heat energy around them under certain conditions, and the speed at which they release their own energy is very, very slow, almost close to a stationary state. ”

Therefore, the nature of the universe can be summed up in this way. The sum of the energy possessed by all matter in the universe, including countless dark matter, black holes, nebulae, stars, planets, moons, flowers and plants on planets, and other animals. The way in which the universe exists is that its own established energy is transferred to each other between different substances within the universe within the maximum expansion of the universe, which is the essential way of the existence of the universe, which does not increase or decrease. ”

Bei Bei looked at her classmates after speaking, all of them looked a little dazed, she realized that she was too involved, so she added: "I'm sorry, classmates, I just mentioned this, it doesn't matter if you can understand it or not, I will tell you about this knowledge in the future." ”

After Bei Bei finished speaking, he looked at Lei Ping and found that he looked at himself as if he was thinking, so there was a trace of shyness on his face, and he turned his face and asked his classmates: "So, please think about it, where does the energy obtained by us humans and all other creatures come from?" ”

The children looked at each other and shook their heads. Zhang Lu and Kong Wenjia, who were behind Beibei, listened to Beibei's speech, but they didn't expect Beibei to be so focused, serious, and organized in class, and Beibei's appearance in class was lively and cute, and they saw Beibei's erudite side as a natural science teacher for the first time.

"Students can think about whether there were plants or animals in this world?" Bei Bei faced the children's confusion and reminded everyone.

"I think it was the plants that came first. Because plants are easy to grow. ”

"I think there should be animals on this earth, animals are more powerful than plants, and they can move freely."

"No, they should have been there at the same time, because ...... Because...... There are so many plants and animals in the sea and on land that it makes more sense to appear together. ”

The children discussed everything you said to me, and some students were thinking about reservations for the time being.