Who knows the origin of human beings
1. The origin of life: 4.6 billion years ago, the newly formed earth was a lifeless world. At that time, the red sun was scorching in the sky, lightning was thundering, and volcanoes were erupting on the ground, with lava overflowing. Gases such as methane, ammonia, hydrogen, and water vapor ejected from volcanoes surrounded the earth's surface, forming the primitive atmosphere. The composition of the original atmosphere was completely different from the current atmosphere. There was no oxygen and no ozone layer. The ultraviolet rays of the sun penetrated directly to the ground. Under the long-term influence of huge natural conditions such as ultraviolet rays, cosmic rays, lightning, and high temperatures, various components in the primitive atmosphere continued to undergo synthesis or decomposition reactions, forming a variety of simple organic compounds, which created the materials for the emergence of primitive life. condition.
Later (about 3.9 billion years ago), the temperature of the earth gradually dropped, but volcanic eruptions were still frequent, and the earth's crust also changed. Some places rose up to form plateaus and mountains, and some places fell down to form depressions. and valley. At the same time, water vapor in the atmosphere continues to increase. When the water vapor reaches a saturated state and cools, it falls to the ground as rainwater and merges into the depression to form a primitive ocean. Simple organic matter in the primitive atmosphere also entered the primitive ocean with rain. In the primitive ocean, these simple organic matter continued to react under certain conditions, and over an extremely long period of time, primitive life gradually formed. Therefore, the primitive ocean is the cradle of primitive life.
Summary: It can be seen from this that primitive life was gradually formed from non-living matter over an extremely long period of time under primitive earth conditions.
Scientists have also conducted a large number of scientific experiments to study the origin of life. In 1965, Chinese biologists for the first time artificially synthesized a simple protein molecule, crystallized bovine insulin. In 1953, American scholar Miller simulated the original atmospheric composition for the first time and synthesized simple organic matter. These experiments are of great significance to people's understanding of the process of the origin of life. Although people still don’t know much about the detailed process of the origin of life, with the development of science and technology and the improvement of research methods, humans will one day reveal all the secrets of the origin of life.
2. The process of biological evolution:
The emergence of primitive life has opened a new era of biological evolution and development. After the emergence of primitive life, due to different nutritional methods, some primitive life evolved into primitive algae that had chlorophyll and lived an autotrophic life; some primitive life evolved into primitive single-cell animals without chlorophyll and relied on the intake of ready-made organic matter. These primitive algae and primitive single-celled animals then evolved into various plants and animals.
This is a tree of animal evolution. From the base of the trunk to the top of the tree shows the evolution of plants and animals. The closer the plants or animals are to the base of the tree trunk, the farther and lower they appear from now; the closer the plants or animals are to the treetops, the closer and higher they appear to be. There are two large branches on the trunk. The one on the left represents the evolution of animals, and the one on the right represents the evolution of plants. On each branch there are many smaller branches, which in turn indicate the evolutionary order and evolutionary status of each group of animals and plants.
1 The process of plant evolution: There are four main groups of plants in nature: algae, bryophytes, ferns and seed plants. Seed plants include gymnosperms and angiosperms.
(1) Most algae plants live in water. They are single-celled and multi-celled. Their structures are relatively simple and there is no differentiation of roots, stems, leaves and other organs.
Question: The characteristics of each biological group reflect their position in the evolutionary process. Based on the characteristics of algae, where should we place it in the biological evolutionary tree?
Answer: The characteristics of algae indicate that the macroscopic world is a lower plant group, so it should be located on the lowest branch of the evolutionary tree.
(2) Bryophytes generally have stems and leaves, but there is no conductive tissue in the stems and leaves. The fertilization process is inseparable from water, and they are suitable for living in a humid environment.
(3) Ferns have real roots, stems and leaves, and have conductive tissue and relatively developed mechanical tissue in the roots, stems and leaves. The plants are taller and cannot be fertilized without water. Most of them Living in a damp environment.
Bryophytes and ferns both evolved from primitive algae over a long period of time. However, judging from the characteristics of the two, ferns are better adapted to terrestrial life than bryophytes. Therefore, ferns are higher than bryophytes.
Due to the structural and reproductive characteristics of bryophytes, the further development of bryophytes into terrestrial life is restricted. However, because ferns can better adapt to terrestrial life, some primitive ferns gradually evolved. Become a seed plant.
Question: Seed plants include gymnosperms and angiosperms. Which of these two categories of plants is more advanced and why?
Angiosperms are more advanced. Because the seeds are coated with a pericarp, which helps protect the seeds, reproduce offspring, and better adapt to life on land, angiosperms are the highest group of plants in the plant world.
Summary: From this, we can summarize the laws of plant evolution. The body changes from single cells to multi-cells, the structure changes from simple to complex, the status changes from low to high, and the living environment gradually transitions from water to land.
2 The process of animal evolution:
Question: How many major groups can animals be divided into?
Answer: Invertebrates and vertebrates.
(1) Let’s first look at the purchase process of invertebrates. Ask students to recall, what are the main phyla of invertebrates?
From a structural point of view, the lowest and most primitive invertebrates are protozoa, which evolved from single-cell protozoa to multi-cell coelenterates; from diblast coelenterates to three-cell coelenterates. Platyhelminthes in the germ layer; anus appeared in linear animals; true body cavity appeared in annelids; arthropods are invertebrates that have truly adapted to land life. In this process, the structure of animals became more and more complex, tissue differentiation gradually appeared, organs and systems appeared, and the living environment gradually changed from water to land.
(2) Among invertebrates, there is a class of animals called echinoderms. Starfish, sea cucumbers, and sea urchins are all in this class of animals. Evolved from primitive echinoderms into primitive vertebrates.
Question: How many classes of vertebrates have we studied?
Vertebrates are higher animals, and the earliest vertebrates that appeared on the earth were ancient fish. Ancient fish lived in water. Later, due to changes in the earth's climate, lakes and ponds dried up. Among the ancient fish, the lobe-finned fish evolved into primitive amphibians over a long period of time.
Amphibians are the first vertebrates to land on land. However, amphibians have not completely escaped the shackles of water. They must lay eggs, hatch and survive the larval stage in water.
Primitive amphibians gradually evolved into primitive reptiles. Reptiles lay eggs and hatch on land, completely getting rid of the constraints of water and becoming true terrestrial animals. The complex and changeable terrestrial living environment provides new ecological environments and adaptive directions for the evolution of animals. Primitive reptiles differentiated and developed in various directions, evolving into primitive birds and mammals respectively.
Summary: From this point of view, like the evolutionary process of plants, animals also evolved from single cells to multi-cells, from simple to complex, from low to high, and from aquatic to terrestrial.
3 From this we can summarize the evolutionary rules of living things: from simple to complex, from low to high, from aquatic to terrestrial.
The emergence of three human beings: In the process of biological evolution, human beings are the product of biological evolution to a higher stage. So what kind of ancient creatures did human beings evolve from?
Like all mammals, the human body also has the basic characteristics of mammals such as homeostasis, viviparity, and lactation. This shows that humans and mammals are closely related. In biological classification, humans belong to the phylum Vertebrates, class Mammalia, order Primates, family Hominidae, genus Homo, and species. In the order of primates, in addition to the Hominidae, there are also the Monidae, Gibbonidae, Anthropoididae, etc.