Journal 2 Geography, Biology

I am a second-year junior high school student, and I would like to give you some information:

Section 1: The Origin of Life

Regarding the issue of the origin of life, there has been a long time ago Various explanations. In recent decades, people have conducted comprehensive research on the origin of life based on new achievements in modern natural science and have made great progress.

According to scientific calculations, the earth has a history of approximately 4.6 billion years from its birth to the present. The early earth was hot, and all elements on the earth were in a gaseous state. There was absolutely no life at that time. The first life evolved step by step from non-living substances through extremely complex chemical processes over an extremely long period of time after the earth's temperature dropped. At present, this statement that the origin of life is through the process of chemical evolution has been recognized by most scholars, and it is believed that this chemical evolution process can be divided into the following four stages.

Generating organic small molecule substances from inorganic small molecule substances. According to speculation, the chemical evolution process of the origin of life began under primitive earth conditions. At that time, the surface temperature of the earth had dropped, but the internal temperature was still very high. Volcanic activity was extremely frequent. The gases ejected from the interior of the volcano formed the primitive atmosphere (Figure 76). It is generally believed that the main components of the original atmosphere are methane (CH4), ammonia (NH3), water vapor (H2O), hydrogen (H2), in addition to hydrogen sulfide (H2S) and hydrogen cyanide (HCN). Under the action of cosmic rays, ultraviolet rays, lightning, etc. that are constantly produced by nature, these gases can naturally synthesize a series of relatively simple organic small molecule substances such as amino acids, nucleotides, and monosaccharides. Later, as the earth's temperature further dropped, these small organic molecules flowed through lakes and rivers with rainwater, and finally collected in the primitive ocean.

The speculation in this regard has been confirmed by scientific experiments. In 1953, American scholar Miller and others designed a closed device (Figure 77). They extracted the air from the device, then simulated the atmospheric composition of the original Earth, introduced gases such as methane, ammonia, hydrogen, water vapor, etc., and simulated lightning under the conditions of the original Earth, continuously performing spark discharges. Finally, the production of amino acids was detected in the U-shaped tube. Amino acids are the basic units that make up proteins, so it is of great significance to explore the production of amino acids on earth.

In addition, some scholars simulated the atmospheric composition of the primitive earth and produced other organic compounds in the laboratory, such as purines, pyrimidines, ribose, deoxyribose, fatty acids, etc. These studies show that in the origin of life, the chemical process of synthesizing organic matter from inorganic matter is entirely possible.

Formation of organic polymer substances from organic small molecule substances. How were organic polymer substances such as proteins and nucleic acids formed under primitive earth conditions? Some scholars believe that in the primitive ocean, small organic molecules such as amino acids and nucleotides accumulated and interacted with each other over a long period of time. Under appropriate conditions (such as adsorption on clay), primitive substances were formed through condensation or polymerization. protein molecules and nucleic acid molecules.

Now, some people have simulated the conditions of the primitive earth and created substances similar to proteins and nucleic acids. Although these substances are still somewhat different from today's proteins and nucleic acids, and it is not yet certain whether the formation process of proteins and nucleic acids on the primitive earth was like this, it has provided some clues for people to study the origin of life. Under primitive earth conditions, it was possible to produce these organic polymers.

Composition of multi-molecular systems from organic polymer substances. According to speculation, organic polymer substances such as proteins and nucleic acids accumulate more and more in the ocean, and their concentrations continue to increase. Due to various reasons (such as evaporation of water, The adsorption of clay), these organic polymer substances are separated after concentration, they interact and condense into small droplets. These small droplets float in the primitive ocean, covered with the most primitive boundary membrane, separated from the surrounding primitive ocean environment, thus forming an independent system, that is, a multi-molecular system. This multi-molecular system has been able to carry out primitive material exchange activities with the external environment.

Evolution from multi-molecular system to primitive life. The evolution from multi-molecular system to primitive life is the most complex and decisive stage in the origin of life. It is directly related to the occurrence of primitive life. Currently, this process cannot be verified in the laboratory. However, we can speculate that some multi-molecular systems have evolved over a long period of time, especially due to the interaction of the two main components of proteins and nucleic acids, and finally formed primitive life with primitive metabolism and reproduction. From now on, we will move from the chemical evolution stage of the origin of life to the biological evolution stage after the emergence of life.

Although a large number of simulation experiments have been conducted regarding the study of the chemical evolution process of the origin of life, most of the experiments only focused on the first stage, and some stages were limited to hypotheses and speculations. Therefore, the issue of the origin of life must continue to be studied and discussed.

Proteins and nucleic acids are the most important substances in living organisms. Without proteins and nucleic acids, there would be no life. In 1965, Chinese scientists artificially synthesized crystalline bovine insulin (a protein containing 51 amino acids).

In 1981, Chinese scientists used artificial methods to synthesize yeast alanine transporting ribonucleic acid (a type of ribonucleic acid). These works reflect our country's major achievements in exploring the origin of life.

Classification system of living things Within 1 billion years after the formation of the earth, primitive life appeared on the earth. After a long period of time, the primitive life gradually evolved into the extremely rich and diverse biological world it is now. Biologists have scientifically classified various organisms based on their basic structural characteristics and from the perspective of biological evolution. With the development of natural science, the classification system of organisms is constantly undergoing new changes. Now briefly described as follows.

Initially, biologists divided life on earth into two kingdoms: plants and animals. Later, some scholars proposed a new classification system based on the two-sphere system. For example, some scholars have proposed a five-kingdom system, namely Prokaryotes, Protista (some species extracted from animals and plants, including Euglena, Chrysophyta, Dinoflagellates, Myxomycetes, Flagellates, Ciliates, Sarcopodia, etc.), plant kingdom, fungi kingdom and animal kingdom. Others advocate adding the virus world to the five world system to form a six world system.

However, for a long time, people have divided the biological world into the plant kingdom and the animal kingdom. This classification method has been used for more than 200 years and is still widely used today.

Section 2: The Evolution of Biology

How did the various creatures on the earth come from? There has been debate about this issue since ancient times. Creationists believe that all living things on earth today were created by God. According to the theory of special creation, there are only as many kinds of creatures as there were originally created, and these creatures were all created at once, and there is no genetic relationship between various creatures. Evolutionists believe that the various living creatures on the earth today were not created by God, but evolved gradually from the same ancestors over a long period of time. Therefore, various living creatures have distant or close kinship relationships with each other. Because evolutionists cite a large number of facts when demonstrating biological evolution, the once-popular creationism is increasingly disbelieved by people, while the theory of evolution is recognized by more and more people.

1 Evidence of biological evolution

There is a lot of evidence of biological evolution. Here we only introduce evidence from three aspects: paleontology, embryology and comparative anatomy.

Paleontological evidence Paleontology is the science that studies the occurrence, development, classification, evolution, distribution and other laws of organisms in geological historical periods. Its research objects are the remains of ancient organisms preserved in the strata. Relics or relics - Fossils.

In the process of studying fossils, paleontologists have discovered that the appearance of fossils of various types of organisms in the strata has a certain order, that is: in the strata formed earlier, the organisms that become fossils are more likely to be fossilized. The simpler, the lower the level; in the later strata formed, the fossilized organisms are more complex, the higher the level. This not only confirms that various modern organisms evolved gradually over a long period of geological time, but also reveals the evolutionary sequence of organisms from simple to complex, from low to high, and from aquatic to terrestrial. The fact that fossils of various types of organisms appear in a certain order in the strata is one of the most reliable evidences of biological evolution.

Through the study of horse fossils, we learned about the evolution of horses. This is an outstanding example of biological evolution in paleontology.

The distant ancestor of modern horses is called Eohorse (Figure 78). It is estimated based on the strata where the Archaeopteryx fossils are buried that it lived in warm, moist grasses and shrubs 50 million years ago. It was as big as a modern fox, with a curved back, a flexible body, and well-developed four toes on its forelimbs. .

In more recent strata, fossils of the horse's more recent ancestor, the three-toed horse, were discovered. The three-toed horse lived in the vast grasslands. Its body was larger than that of Eohorse, and its limbs were also lengthened. The front limbs only had three toes, and the middle toe was developed and became the only toe that touched the ground.

Horse fossils after the three-toed horse prove that the horse's body gradually became taller, the toe end of the middle toe formed a hard hoof, and the toes on both sides degenerated into remains. This kind of horse is suitable for running on the vast grassland. This series of horse fossils vividly illustrates that modern horses gradually evolved from the smaller Eohorse over a long period of geological time.

In paleontological research, some intermediate transitional animal fossils and plant fossils have also been discovered. These fossils also provide strong evidence for the theory of biological evolution. For example, the fossils of Archaeopteryx are important evidence that birds evolved from ancient reptiles; the fossils of seed ferns prove the evolutionary relationship between seed plants and ferns.

Geological time Geological time refers to the time and sequence in the formation process of rocks of different ages on the earth's crust. According to the method of paleontology, the geological era can be divided into the Archean Era, the Proterozoic Era, the Paleozoic Era, the Mesozoic Era and the Cenozoic Era, and then each era can be divided into several eras. The order in which various types of organisms appear in geological time is shown in the geological time table on the next page (the number of years in the table is an estimate).

Evidence from Embryology Embryology is the science that studies the embryonic formation and development of animals and plants. It also provides important evidence for the theory of biological evolution.

People have long noticed that the embryonic development of all higher organisms (such as vertebrates and seed plants) begins with a fertilized egg. This situation can illustrate that higher organisms originated from single-celled organisms.

Let's compare seven vertebrate species and human embryos. As can be seen from Figure 79, the embryos of these seven animals and humans are very similar in the early stages of development, that is, they all have gill slits and tails. By the late stage of development, except for fish, the gill slits of other animals and humans have disappeared. , the human tail also disappeared. Now I have to ask: The shapes of these animals and humans are very different when they are adults. Why are they so similar in the early stages of embryonic development? Gills are organs suitable for water breathing. Why do terrestrial vertebrates and humans also have gill slits in the early stages of embryonic development? Since humans are tailless, why do humans also have tails during embryonic development?

These all show that higher vertebrates evolved from some lower vertebrates in ancient times. In other words, both vertebrates and humans evolved from the same ancient primitive ancestor, so their embryos are very similar in the early stages of development. The same primitive ancestors of ancient vertebrates lived in water, so gill slits appeared during embryonic development of terrestrial vertebrates and humans. Humans evolved from animals with tails, so a very obvious tail will appear during embryonic development.

Evidence from Comparative Anatomy Comparative anatomy is the science of dissecting and comparing the organs and systems of various vertebrate animals. The most important evidence that comparative anatomy provides for the theory of biological evolution is that of homologous organs.

Homologous organs refer to organs that have the same origin, similar structure and parts, but different shapes and functions. For example, bird wings, bat chiropterans, whale fins, horse forelimbs and human upper limbs are very different in appearance and function, but when comparing their internal structures, they are basically the same. That is, they are all composed of humerus, radius, ulna, carpus, metacarpal and phalanges, and are arranged in basically the same way (Figure 80), and they are all homologous organs. The existence of homologous organs proves that all organisms with homologous organs evolved from the same primitive ancestor. However, in the process of evolution, due to their different living environments, homologous organs adapted to different living environments, and gradually appeared morphological and functional differences. Therefore, the same forelimbs, the wings of birds and the chiropterans of bats, become suitable for flying, the fins of whales become suitable for swimming in the water, the forelimbs of horses become suitable for running, and the upper limbs of humans become suitable for doing things. All kinds of complex actions.

Section 1 The relationship between organisms and the environment

1 The impact of the environment on organisms

The living environments of organisms are diverse. From the top of the mountains to the depths of the ocean, from vast deserts to dense forests, from cities to rural areas, there are living things everywhere. In different environments, the types of organisms vary greatly (Figures 82, 83, 84, and 85).

The concept of ecological factors No matter what environment living creatures live in, they are affected by various factors in the environment. Taking wheat as an example, its growth and development is not only affected by abiotic factors such as sunlight, temperature, and water, but also by biotic factors such as wheat aphids, locusts, and mice. Factors in the environment that affect the morphology, physiology, and distribution of organisms are called ecological factors.

Abiotic factors There are many kinds of abiotic factors. The following only describes the effects of three abiotic factors on living things: sunlight, temperature and water.

Sunlight Without sunlight, plants cannot carry out photosynthesis and cannot survive. Therefore, sunlight plays a decisive role in plant physiology and distribution. On land, some plants can only grow well under strong light, such as pine, fir, willow, locust, wheat, corn, etc. During the wheat filling period, continuous rainy weather will cause a reduction in wheat production. Some plants can only grow well in the shade of the lower layer of dense forests, such as medicinal plants ginseng and Panax notoginseng. In the ocean, as depth increases, the light gradually weakens, and the types of plants distributed also vary. When someone investigated a certain bay, they found that there were a lot of green algae growing in the shallow water, a lot of brown algae growing in the deeper water, and a lot of red algae growing in the deeper water. The limit that sunlight can reach is 200 meters below the sea surface. Therefore, it is difficult for plants to survive in waters below 200 meters. In addition, the length of sunlight also affects the flowering period of plants. Some plants require a longer period of sunlight to bloom, and these plants only bloom in late spring and early summer, such as alfalfa, iris, spinach, etc.; some plants require a shorter period of sunlight to bloom, and these plants bloom in autumn, such as Asteraceae. plant. There are also some plants that are not strict about the length of sunlight and can bloom in different seasons.

The impact of sunlight on animals is also obvious. Sunlight can affect an animal's body color. For example, the back of a fish's body is darker in color, but its belly is white, which is related to the influence of sunlight. Sunlight can affect an animal's vision. Some animals can hardly see anything at night, such as chickens; some animals have very good vision at night, such as owls. The length of daylight hours has an impact on the reproductive activities of animals. Trout often spawn in December because their reproductive organs need the stimulation of short days to mature. Sunlight can also affect the growth and development of animals.

Someone has done such an experiment: when aphids are cultured under conditions of continuous light or continuous no light, most of the individuals produced have no wings; when aphids are cultured under conditions of alternating light and dark, most of the individuals produced have wings. In terms of living habits, some animals have phototaxis, such as moths. Moths are very sensitive to ultraviolet light, so people often use black lights at night to trap and kill these agricultural pests.

Temperature The temperature in the universe changes greatly, and the temperature range in which living things can survive is very narrow. Overheating or overcooling will prevent the normal metabolism of living organisms, and even cause the death of living organisms. Taking animals as an example, most animals live in a temperature range of about -2 to 50°C. If the ambient temperature exceeds this range, many animals will have difficulty surviving.

Temperature has an important influence on the distribution of plants. In forests in cold zones, there are more coniferous forests; in forests in warm zones, there are more broadleaf forests. Fruit trees such as apples and pears are not suitable for planting in tropical areas, and citrus trees are not suitable for planting in the north. These are due to temperature restrictions.

Temperature can affect the morphology of animals. Some people have found that individuals of the same type of mammals living in cold areas are larger in size, but have shorter tails, ears, noses, etc. This can reduce the surface area of ??the body and thereby minimize heat loss. For example, foxes that live in the Arctic have much smaller ears than big-eared foxes that live in the deserts of Africa (Figure 86).

Temperature also has a significant impact on the living habits of animals. In the hot summer, birds are mainly active in the cooler hours of morning and evening, and become dormant at noon. Some animals hibernate in caves during the summer, such as snails. When the temperature drops below 24°C, grasshoppers (commonly known as cicadas) stop chirping. When winter comes, many cold-blooded animals will enter hibernation, such as snakes, lizards, etc.

Water We know that all living things cannot live without water. Among the various chemical components in living organisms, most are water. Therefore, water is also an important ecological factor affecting the survival of organisms.

For animals, lack of water has more serious consequences than lack of food. Animals can survive longer without food than without water.

The total amount of precipitation in a year and the distribution of rainy seasons are important factors that limit the distribution of terrestrial organisms. In arid desert areas, only a few drought-tolerant animals and plants survive; while in tropical rainforest areas with abundant rainfall (such as Hainan Island in southern my country), there are dense forests and a wide variety of animals and plants.

Biological factors Every living thing in nature is affected by many living things around it. Among these creatures, there are both the same species and different species. Therefore, biological factors can be divided into two types: intraspecific relationships and interspecific relationships.

Intra-specific relationships: In intra-specific relationships, there are both intra-specific mutual aid and intra-specific struggles.

Intraspecific mutual aid is common. For example, many kinds of animals often gather in groups during their lives and live a gregarious life. There are two main types of this kind of gregarious lifestyle: one type is the gregarious life lived by social insects such as ants and bees. There is a clear division of labor between individuals and they work together to maintain the group. survival. It is often seen that many ants attack a large insect together and carry it to the nest. When a bee stings an enemy, it releases a pheromone that prompts other bees to attack the enemy together. Another type, unlike social insects, has no clear division of labor among members of the swarm. This type of swarming can often be seen in some insects (such as migratory locusts), fish, birds and mammals. They gather in groups, roam in a certain area and along a certain path, looking for food together. At the same time, this kind of group life is also beneficial to hunting or defending against enemies. In terms of predation, packs of wolves can prey on animals that are larger than themselves. As far as defense is concerned, groups of musk oxen can effectively deal with wolf attacks. When musk oxen live alone, they are often hunted by wolves. However, when they gather in a group, if they encounter a wolf pack, the male cows will form a circle with their heads facing outward, surrounding the female cows and calves. In this way, it will be difficult for the hunting wolves to succeed.

In terms of intraspecific struggle, the phenomenon of struggle between individuals of the same species due to conflicts over food, shelter, finding mates or other living conditions also exists. For example, in some bodies of water, if there are no other fish except bass, the adult bass will feed on the juveniles of the species. Frog tadpoles can excrete a toxic substance from their intestines. In a pond with a high tadpole density, if this toxic substance increases, it will inhibit the growth and development of tadpoles and increase the mortality of young tadpoles. Male individuals of some animals often fight with males of the same species during the breeding period for females. The above-mentioned intraspecific struggle is harmful to the failed individual and may even cause death. However, it is beneficial to the survival of the species. It can enable the surviving individuals within the same species to obtain relatively sufficient living conditions, or enable the offspring to survive. The offspring can be better.

Interspecies relationship refers to the relationship between organisms of different species, including parasites, parasitism, competition, predation, etc.

Biology: Two organisms live together, depend on each other, and benefit each other; if they are separated from each other, both or one of them cannot survive independently. This kind of sexual and living relationship between two organisms is called sexual intercourse. A classic example of a lichen is a lichen. Lichens are organisms of fungi and algae (Figure 87).

Lichen is a plant, but it is not a simple plant, but is composed of fungi and algae. Algae contain chlorophyll, which enables photosynthesis and provides organic matter for fungi. Fungi absorb water and inorganic salts to supply the needs of algae. In lichens, the relationship between fungi and algae is mutually beneficial and interdependent.

Parasitism: An organism lives in or on the body of another organism and absorbs nutrients from there to maintain life. This phenomenon is called parasitism. The phenomenon of parasitism is very common in the biological world. For example, roundworms, tapeworms, and schistosomiasis are parasitic in the bodies of other animals. Lice and fleas are parasitic on the bodies of other animals. Cuscuta is parasitic on leguminous plants (Figure 88). Bacteriophages are parasitic on bacteria. Interior, etc.

Competition: The phenomenon in which two organisms live together and fight for resources, space, etc. is called competition. The result of competition is often unfavorable to one party, or even eliminated. For example, someone once conducted an experiment: when two species of Paramecium, the large and the small, were cultured separately, they both grew normally. However, when the two were cultured together, after 16 days, one of them was completely dies, while the other continues to grow normally.

Predation: A predatory relationship occurs when one organism feeds on another. For example, herbivorous rabbits feed on certain plants, carnivorous wolves feed on rabbits, and so on.

In summary, organisms are affected by many ecological factors, and these ecological factors together constitute the living environment of organisms. Living things can only survive if they adapt to their environment.

Section 2 Populations and Biomes

In nature, every living thing does not exist alone, but lives together with other living things. Among these biological individuals, there are both those of the same species and those of different species, and there is a relationship between them that is both interdependent and mutually restrictive.

The concept of population The sum of individuals of the same species in a certain space and time is called a population. For example, all the carp in a lake are a population, which is composed of fry, small fish, and large fish; all the cotton aphids in a cotton field are a population, which is composed of young aphids, winged and wingless mature aphids. All the beech trees in a forest are also a population, which is composed of beech trees of different ages.

Characteristics of a population A population is not a simple sum of many individuals of the same species, but an organic unit. It has characteristics such as population density, age composition, sex ratio, birth rate and death rate. These characteristics are individually biological individuals do not possess.

Population density Population density refers to the number of individuals of a certain group in unit space. For example, the number of African crucian carp per cubic meter of water in a fish pond; the number of Apoderma agrarian rats per square kilometer of farmland, etc.

Population densities of different species tend to vary widely. For example, in one place in my country, there are less than two wild ass per 100 square kilometers, while there are hundreds of thousands of gray hamsters in the same area.

The population density of the same species also varies under different environmental conditions. For example, the population density of East Asian migratory locusts in a farmland is high in summer and decreases in late autumn when the weather is colder.

Age composition The age composition of a population refers to the proportion of the number of individuals of each age group in a population. The age composition of the population can be roughly divided into three types (Figure 93): (1) Growth type: There are many young individuals in the population and few old individuals. Such a population is in a period of development, and the population density will become larger and larger. (2) Stable type: The proportion of individuals of each age group in the population is moderate. Such a population is in a stable period, and the population density will remain stable for a period of time. (3) Decline type: There are fewer young individuals in the population, but more adult and old individuals. Such a population is in a period of decline, and the population density will become smaller and smaller.

Sex ratio The sex ratio of a population refers to the proportion of male and female individuals in the population. Populations of different species have different sex ratios, which can be roughly divided into three types: (1) Males and females are equal, which is more common in higher animals, such as chimpanzees, orangutans, etc. (2) There are more females than males, and they are more common in artificially controlled populations, such as chickens, ducks, sheep, etc. Some wild animals also have more females than males during the breeding period, such as elephant seals. (3) There are more males than females, and they are more common in insects that live a social life, such as termites. Sex ratio affects population density to a certain extent. For example, the use of synthetic sex attractants to lure male pest-killing individuals destroys the normal sex ratio of the pest population, causing many female individuals to be unable to complete mating, thus significantly reducing the population density of the pest.

Birth rate and death rate Birth rate refers to the number of new individuals produced per unit time in a population. For example, one peacebird population has a birth rate of 7.8 chicks per female per year. Mortality rate refers to the number of individuals that die per unit amount of time in a population.

For example, in a certain argali population, for every 1,000 individuals who lived to be 6 years old, the mortality rate during the age interval of 6 to 7 years was 69.9. Birth and death rates are also important factors in determining population size and population density.

The concept of biological community is the sum of various biological populations living in a certain natural area and having direct or indirect relationships with each other. It is called biological community, or community for short. For example, on a grassland, there are plants such as grass and weeds, animals such as insects, birds, mice, and microorganisms such as bacteria and fungi. All these organisms live together and are closely related to each other. , thus forming a community.

The structure of a biological community The structure of a biological community refers to the spatial configuration of various organisms in the community, including vertical structure and horizontal structure.

Vertical structure In the vertical direction, the community has obvious stratification. For example, in a forest, tall trees occupy the upper layer of the forest, followed by the shrub layer and herbaceous layer below (Figure 94). There is a similar stratification phenomenon in the vertical distribution of animals in communities. For example, in the valley forest of Mount Everest in my country, there is a kind of bird that always moves in groups in the upper levels of the forest and eats the seeds of tall trees. Birds such as the Coal Tit, Yellow-rumped Warbler and Orange-Red Flycatcher always nest in the middle levels of the forest. Blood Pheasant and Brown-tailed Pheasant are typical forest bottom birds, eating moss and insects on the ground.

Horizontal structure In the horizontal direction, due to the influence of terrain fluctuations, light intensity, humidity and other factors, the biological species in different areas are often different. For example, in a forest, at the base of trees and other places covered by the canopy, the light is darker, suitable for mosses and shade-loving plants to survive, while in the gaps in the canopy or other places with sufficient light, there are more Shrubs and grass.

In summary, for organisms in a certain area, individuals of the same species form populations, and different populations form communities. Characteristics such as population density and community structure are closely related to various ecological factors in the environment.