Marine popular science knowledge materials

How did the ocean form? Where does the sea water come from?

At present, science cannot give the final answer to this question, because they are related to another common and equally unsolved problem of the origin of the solar system.

Current research proves that some large and small nebulae separated from the solar nebula about 5 billion years ago. They revolve around the sun while rotating. In the process of movement, they collided with each other, and some lumps combined with each other, from small to large, and gradually became the original earth. During the collision of nebula clusters, they shrink sharply under the action of gravity, and the radioactive elements in them degenerate, which makes the primitive earth heat up continuously. When the internal temperature reaches high enough, underground substances, including iron and nickel, begin to melt. Under the action of gravity, the weight sinks and tends to concentrate in the center of the earth, forming the core; Lighter ones float to form the crust and mantle. At high temperature, the water inside evaporates, rushes out with the gas and rises into the air. But because of gravity, they will not run away, but will only turn around the earth and become a circle of air and water.

In the process of cooling and condensation, the crust on the earth's surface is constantly impacted and squeezed by the violent movement inside the earth, so it becomes uneven and sometimes crushed, forming earthquakes and volcanic eruptions, spewing magma and hot gas. At first, this kind of situation often happens, and then it gradually decreases and tends to be stable. This division of light and heavy substances led to great turmoil and reorganization, which was completed about 4.5 billion years ago.

After the crust is cooled and shaped, the earth is like an apple that has been dried for a long time, and its surface is wrinkled and uneven. There are mountains, plains, river beds and basins.

For a long time, the water vapor in the sky coexisted with the atmosphere. Thick clouds are gathering. It's dark. With the gradual cooling of the earth's crust, the temperature of the atmosphere is also slowly decreasing. Water vapor takes dust and volcanic ash as condensation nuclei and becomes water droplets, which accumulate more and more. Due to uneven cooling and strong air convection, thunderstorms and turbidity currents were formed, and it rained harder and harder for a long time. Surging floods, through thousands of rivers and valleys, converge into a huge water body, which is the primitive ocean.

In the primitive ocean, seawater is not salty, but acidic and anoxic. Water is constantly evaporating, and clouds repeatedly cause rainfall, and then fall back to the ground, dissolving the salt in the rocks on the land and under the sea, and continuously collecting it into the seawater. After hundreds of millions of years of accumulation and integration, it has become a generally uniform salt water. At the same time, because there was no oxygen and ozone layer in the atmosphere at that time, ultraviolet rays could reach the ground directly. With the protection of seawater, life was first born in the ocean. About 3.8 billion years ago, organic matter was produced in the ocean, and lower single-celled organisms first appeared. In the Paleozoic era 600 million years ago, there were algae that photosynthesized in the sun to produce oxygen, which gradually accumulated and formed the ozone layer. At this time, creatures began to land.

In a word, after the gradual increase of water quantity and salinity and the vicissitudes of geological history, the primitive ocean gradually evolved into today's ocean.

Generation of ocean currents

The water in the sea always flows in a regular and clear form, which is called ocean current. One of the most famous is the Gulf Stream, which is 50 miles wide at its narrowest point and has a velocity of 4 miles per hour. It goes north along the North American coast, crosses the North Atlantic, and regulates the climate in northern Europe. The North Pacific Ocean current is a similar warm current, which flows from the tropics to the north, raising the temperature on the west coast of North America.

The prevailing wind is the main force to keep the water moving. The different density of seawater is also one of the reasons for ocean currents. The density of cold water is higher than that of warm water, so cold water sinks and warm water rises. Based on the same principle, the cold water near the poles will also sink and flow to the equator below the sea surface. When it reaches the equator, the current rises, replacing the warm water flowing to the poles with surface current.

The coast and mainland of the island also have an influence on the current, either turning the current or dividing it into tributaries. Generally speaking, however, major ocean currents circulate around ocean basins. Due to the influence of the earth's rotation, the current in the northern hemisphere flows clockwise, while in the southern hemisphere it is the opposite.

Seawater salinity

The salt content of seawater varies from place to place, averaging around 3.5%. Among these inorganic salts dissolved in seawater, the most common one is sodium chloride, that is, daily salt.

Some salt comes from volcanoes under the sea, but most of it comes from rocks in the earth's crust. Rock is decomposed by weathering, releasing salt, which is carried to the sea by river water. In the circulation process of seawater evaporation and then condensation into water, after seawater evaporation, salt remains and gradually accumulates to the existing concentration.

The ocean contains so much salt that it can spread a salt layer about 500 feet thick on the global land.

wave

The waves keep rolling on the sea, sometimes as flat as a mirror, and sometimes the waves are huge. Except those caused by earthquakes or volcanic eruptions, waves are mostly caused by winds blowing through the ocean. Waves aroused by storms in the distance may travel hundreds of miles to the coast.

The height between the waves from the peak to the bottom of the trough is mostly less than 10 foot. But in a storm, the waves may be surprisingly high; 1933, the waves recorded in the Pacific Ocean were as high as 1 12 feet.

continental shelf

Some land, such as volcanic islands, will fall steeply into the sea. But around the mainland, most of them are frame landmasses covered by shallow sea, which is an extension of the mainland and is called the continental shelf. The continental shelf usually dips down to about 650 feet below sea level, and then drops sharply to the bottom of the sea. The steep side of the continental shelf is called continental slope. Most continental shelves extend about 50 miles offshore; Some are much narrower; However, the continental shelf on the northern shore of Siberia is 800 miles wide and extends to the Arctic Ocean. Most of the world's catches come from the rich waters on the continental shelf; Countries even claim sovereignty over the continental shelf off their coast, taking oil, mineral deposits and other commodity sources as their own.

Island (in the sea)

An old navigator once said, "The islands in the ocean are like the stars in the sky, and no one can count them." This sentence describes the number of islands in the world. So far, it is difficult to tell the exact number of islands in the world's oceans. Some people say that it is around 200,000, and some people say that it is around 65,438+10,000. Which statement is closer? It depends on what method and standard you use to calculate.

In the ocean, some places show a few square meters of rocks on the water; Coral reefs in some places are like strings of pearls, scattered on the sea. When the tide receded, rows of coral reefs were exposed. When the sea level rises, shellfish are submerged. If these rocks and beaches exposed to the sea are counted as islands, it may be reasonable to say that there are more than 200 thousand islands in the world.

According to the statistics of the number of islands published in the atlas published by various countries in the world, there are about 654.38+million islands in the world, which is well-founded. However, the standards and methods of statistical calculation in the world are not exactly the same: some regard reefs with 10 square meter or 100 square meter as islands; Some regard a small piece of land in the ocean of 500 square meters or even 1 square kilometer as an island. Obviously, the number of statistics by different standard methods is different. Take Indonesia, which has the largest number of islands in the world, as an example. According to the statistics of relevant departments of the Indonesian government, it is more than13,000, and according to the statistics of the Indonesian navy, it is17,000. The number of islands counted by different departments in a country differs by about 4000.

The area of islands in the world is about 9.77 million square kilometers, accounting for115 of the total land area.

adventure on unknown seas

The science that studies the ocean is oceanography.

As early as prehistoric times, human beings have been traveling on the ocean, fishing from the ocean, making a living from the ocean and exploring the ocean. Before the development of aviation, navigation was the main mode of intercontinental transportation and travel.

The exploration of the deep seabed didn't really begin until the middle of the 20th century. Although people know little about diving balls and submarines in the deep sea today.

The relationship between ocean and climate

The ocean is one of the most important factors that determine the development of the earth's climate. The ocean itself is a heat storage body on the earth's surface. Ocean current is a heat energy conveyor belt on the earth's surface. The gas exchange between the ocean and the air (the most important of which is water vapor, carbon dioxide and methane) has great influence on climate change and development.

marine ecology

The ocean is the living environment for many animals and plants. Green algae in the ocean is one of the main producers of atmospheric oxygen. Tropical coral reefs are the most species-rich ecosystems on earth (even richer than tropical rainforests). Humans still know little about deep-sea creatures.

There are many animals and plants in the ocean that are not found on land, and there are more species than on land.

Abundant marine biological resources

With the increase of population and the development of industry, the per capita cultivated land area is gradually shrinking. The whole world is concerned about how the earth can feed human beings. The focus of attention should not be limited to further developing agriculture and animal husbandry on land, but also actively developing and utilizing the vast ocean. There are abundant biological resources in the ocean, which can not only be used to build mariculture farms, but also have many uses to be developed.

Offshore farming and animal husbandry factories have been paid attention to by all countries since 1980s. Japan first proposed to build offshore farms, and from 65438 to 0980, it began to implement a nine-year "ocean take-off plan" to vigorously develop marine aquaculture. By the end of 1980s, the output of aquaculture had exceeded 2 million tons, ranking first in the world. In the 1980s, the United States also invested more than $654.38 billion to build 654.38 million mu of marine farms. Although the former Soviet Union gave priority to offshore fishing, it did not relax its mariculture, throwing sturgeon larvae in the Caspian Sea and the Azov Sea, catching them when they grew up, and establishing oyster and scallop farms along the far east coast. During this period, other countries also set off an upsurge of developing mariculture. Recently, China has also paid attention to the implementation of mariculture, becoming a big shrimp farming country in the world.

Since 1980s, the world mariculture output has increased at the rate of 10% per year, and by the end of 1980s, the mariculture output was estimated to have exceeded 8 million tons. But from the whole marine fishery, the proportion of mariculture in the world is still relatively small, less than 10%, so there is still great potential to be developed.

Many high technologies are being used to improve fish species. For example, using genetic engineering technology to cultivate and improve the fry and larvae of fish, shrimp and shellfish to make them grow fast, have strong vitality and have good meat quality.

1984, the breeding yield of shellfish and abalone in the United States increased by 25% through gene recombination technology. According to the reasons for the discovery of growth hormone in several fish, the gene isolation and transfer experiments were carried out. 1986 successfully transferred the growth hormone gene of rainbow trout into catfish, which shortened the breeding cycle of catfish by more than half. The antifreeze gene was isolated from Antarctic fish and transferred to Atlantic salmon, which increased the cold resistance of salmon and expanded its breeding area. It is of great significance to study the sex control of fish by cell engineering and cultivate all-female salmon, prawns and all-male tilapia. At present, it is being studied to make some swimming fish respond to sound waves and light by controlling genetic genes, so as to manage it scientifically.

In addition to variety improvement, high technology is also used to build seawater farms. The establishment of artificial reefs is an example. It is to build a comfortable home for fish and attract more fish to live and multiply here. Artificial reef is to pile stones, cement blocks, waste vehicles, waste tires and so on on the seabed in various ways, thus creating an environment that marine life likes, and tiny marine life and seaweed will attach to it, providing rich bait for fish. In addition, the artificial reef protruding from the seabed will make seawater flow from the bottom to the upper layer, bring up the nutrient-rich seawater on the seabed, increase its fertility, and thus attract fish.

It is estimated that the ocean can provide 3 billion tons of aquatic products for human beings every year without disturbing the balance. Based on the global population reaching 6.3 billion in 2000, each person can get an average of 476 kilograms per year and 39 kilograms per month. Judging from the output of protein alone, the ocean can produce about 400 million tons of protein every year, which is about seven times the current demand for protein. It can be seen that the ocean can play a great role in solving the problem of human eating. Of course, this goal cannot be achieved overnight.

Scientific and interesting classification of fish

There are more than 20 thousand kinds of fish on the earth. How to distinguish their different categories is not only a rigorous work including the science of biological taxonomy, but also a fascinating topic.

As we know, modern taxonomy (including the classification of fish) mainly includes phylum, class, order, family, genus and species, and some grades can be added when necessary, such as subphylum, superclass, suborder, suborder, subfamily and subgenera. As a species, organisms are real, not artificially classified. There are all kinds of creatures in nature. In most cases, there are clear boundaries between species. Species exist in the form of populations, and there is reproductive isolation between different species.

Generally speaking, there are three specific ways of biological evolution: one is to differentiate from one group into two groups with little difference; Second, specializing in a specific direction of an individual leads to great changes in some aspects of morphological structure; Third, from low to high, from simple to complex, the so-called "complex evolution". In particular, the evolution of organisms is intertwined, including specialization and degradation. Therefore, the first approach is usually represented by subspecies, species and genera, while some genera, families and orders are consistent with the second approach, while some orders, classes and phyla are consistent with the third approach. According to natural conditions. Arrange the realistic natural system.

Fish can be classified in two ways. One is to take one or several characteristics of fish's external morphology and habits as the classification standard, which does not involve kinship and does not consider the basic structure and evolutionary relationship of fish. This classification depends on people's subjective opinions. The other is based on the knowledge of fish morphology, ecology, physiology, genetics and fossil evolution, which is a natural classification. With the development of science and technology, some new methods have appeared in taxonomy. Such as cell classification, chemical classification and molecular classification.

In 1844, Miao Lei listed fish as a class of vertebrates for the first time, which was divided into 6 subclasses, 14 orders. Since then, Reagan, goodrich and Joan Dan have used their own methods to classify fish. 1955, in his book Taxonomy of Modern and Fossil Fishes, Berger classified the existing and ancient fishes into 12 class and19 order, each class, order and family has its own characteristics. In 1966, Greenwood, Rosen, etc. In 197 1, Lars divides fish into cartilaginous fish and bony fish. 1994, Nelson made a more systematic classification of fish. In his book Fish in the World, he completely classified fish according to the principles of orthopedics, phylogeny, embryology, morphology, comparative anatomy, paleontology and comparative biochemistry.

At present, marine fish in the world are divided into cephalopods and spinal propulsion. The fish of Cephalopoda, the notochord and neural tube run through the whole body, and remain unchanged for life, headless and spineless. Without cartilage and hard bones, the heart is a beating abdominal blood vessel. Erythrocyte: hepatic diverticulum, sarcomere: epidermis is composed of monolayer cells. There are many branchial pores, which open in the peribranchial cavity. The original renal ducts are arranged in sections, with the same ducts and openings respectively. They have an inner column and no real brain, but they have two pairs of lobes and nerves, and the upper and lower branches of the spinal nerve are not connected. The gonads are arranged in sections, and there is no fossil record yet. Fish with these characteristics can be named Cephalotaxuinae sequence.

Currently, only amphioxus belongs to this subfamily. Vertebrate fish are divided into: Ankylidae, Blind Eel, Cephalopoda; There are jaws, cartilaginous fishes, cephalopods, animal kingdom, Carnivora, coelacanth, foraminifera and lung fishes, kiwifruit, chondroscleroderma, neofin fishes, etc. The characteristic of legless fish is that they have no jaws. There are 84 species belonging to 2 families 12 genera in the world. Jagnatha marine fish first appeared in the early Silurian spiny fish. It also includes cartilaginous fishes (divided into 2 subclasses, 13 orders, 45 species, 170 genus, about 846 species), fleshy fishes and radial fishes (2 subclasses, 4 subclasses, 9 orders, 42 orders, 43 1 family, 4075 genera).

When you find a species that has no record in history, you can designate it as a new species, but before you designate it as a new species, you should consult the zoological records. Find out the literary topics of a certain group from this book, and then check the original text and identify it. When determining the new species, we should also choose the type specimen, that is, the specimen determined according to the description of the new species. This type specimen generally includes normal mode, sub-mode, combined mode, selected mode and new mode. When you report the discovery of new species, be sure to indicate the location where the type specimens are kept and the type of model used for verification. When naming a new species, sp.nov or n.sp should be appended to the species name to indicate the new species.

Breeders follow the priority rule, and whoever is founded first will use his name. If carp is recognized by Linnaeus, it will be marked as Cyprinus Carpio Linnaeus. If the discoverer of the name of a new species mistakenly lists a new species as another genus, or a genus is later divided into several genera, or even the species is moved to another genus, then the name of the original species will still be retained, but the name of the original species should be placed in brackets. For example, the barracuda Ugil Haematocheila Temmink et schlegel was changed to a lizard (Temmink et schlegel). When writing, the first letters of doors, classes, orders, families and genera are capitalized, and the first letters of species are lowercase. The first letter of the breeder should be capitalized. If two people agree on a species, write an et or&; It means "harmony".

The world's four oceans

The land on the earth is widely distributed and separated from each other, while the sea water extends in all directions and is integrated. This continuous body of water constitutes the world's oceans. The world's oceans are dominated by oceans and are composed of the surrounding seas. There are four oceans in the world: the Pacific Ocean, the Atlantic Ocean, the Indian Ocean and the Arctic Ocean. There are as many as 54 major sea areas, such as Mediterranean Sea, Caribbean Sea, Baltic Sea, Red Sea and South China Sea. Now, let's travel around the world!

Pacific Ocean

The Pacific Ocean is the ocean with the widest area, the deepest depth and the most marginal seas and islands in the world. According to more data, it was first discovered and named by Spanish explorer Pascal, and the word "Taiping" means "peace". /kloc-in the 6th century, Spanish navigator Magellan entered the Pacific Ocean from the Atlantic Ocean via strait of magellan and arrived in the Philippines. During his voyage, the weather was clear and calm, so he named this sea area "Pacific Ocean" in unison. The Pacific Ocean lies between Asia, Oceania, America and Antarctica. The Bering Strait at the northern end is connected with the Arctic Ocean, south to Antarctica, and connected with the Atlantic Ocean and the Indian Ocean to enter the waters around the Antarctic continent. The Pacific Ocean is about 15900 km long from north to south and about 109900 km wide from east to west. The total area is 6.5438+0.7868 million square kilometers, accounting for one third of the earth's surface area and half of the world's ocean area. The average depth is 3957m, and the depth is11034m. There are 6 trenches over 10,000 meters in the world, all of which are concentrated in the Pacific Ocean. The seawater capacity of the Pacific Ocean is 70765438+ million cubic kilometers, ranking first in the world. The Pacific Ocean is rich in resources, especially fishery, aquatic products and mineral resources. Its catch, reserves and grade of polymetallic nodules rank first in the world's oceans.

the Atlantic

The Atlantic Ocean is the second largest ocean in the world. It is located between North and South America, Europe, Africa and Antarctica, and it is an S-shaped ocean belt running north and south. It is about1.5000 km long from north to south, narrow from east to west and 2800 km wide. The total area is about 9 1.66 million square kilometers, slightly more than half of the Pacific Ocean. The average depth is 3626 meters, and the deepest point is 92 19 meters, which is located in the Puerto Rico trench. Marine resources are abundant, rich in fish, and the catch accounts for about one-fifth of the world. Shipping in the Atlantic is particularly developed. East and west communicate with the Indian Ocean and the Pacific Ocean through Suez Canal and Panama Canal respectively, and their freight volume accounts for more than two-thirds of the world's total freight volume.

the Indian Ocean

The Indian Ocean is the third ocean in the world. Located between Asia, Oceania, Africa and Antarctica. It covers an area of about 76 1.7 million square kilometers, with an average depth of 3,397 meters and a depth of 7,450 meters in the Java trench. In the middle of the seabed, there is a ridge that runs roughly north-south. Most of them are located in the tropics with an average water temperature of 20℃-27℃. Its marginal sea, the Red Sea, has the highest salt content in the world.

Oil is the most abundant marine resources, and the Persian Gulf is the world's undersea oil producing area. The Indian Ocean is the earliest navigation center in the world, and its waterway is the earliest discovered and developed in the world, which is an important channel connecting Africa, Asia and Oceania. Marine freight volume accounts for more than 10% of the world, among which oil transportation ranks first.

Arctic Ocean

The Arctic Ocean is located in the northernmost part of the earth, roughly centered on this North Pole, between Asia, Europe and the north shore of North America. It is the smallest and shallowest of the four oceans. The area is about 6.5438+0.479 million square kilometers, accounting for only 3.6% of the world's ocean area; The volume is16.98 million cubic kilometers, accounting for only1.2% of the world ocean volume; The average depth1300m is only one third of the average depth of the world's oceans, and the depth is only 5449m. The Arctic Ocean is also the coldest ocean among the four oceans, with snow all year round and ice thousands of miles thick. The solid ice layer covering the ocean surface is 3 ~ 4 meters thick. Whenever the seawater here flows south into the Atlantic Ocean, clusters of huge icebergs can be seen everywhere, drifting away, just like some terrible monsters, posing a certain threat to the human shipping industry. In addition, there are two wonders in the Arctic Ocean. The first wonder: almost half of the year, continuous darkness, like a long night to see the sun; The other half of the day, mostly sunny, only daytime, no night. Because of this, a day and a night in the Arctic Ocean seems to be a day instead of a year. In addition, in the ocean, you can often see the aurora phenomenon in the Arctic sky, which is erratic, changeable, colorful and very gorgeous. This is the second wonder of the Arctic Ocean.