The World Ocean and its parts. Ecological zones of the world ocean and inland waters Deep zones of the world ocean

• to form knowledge about the World Ocean, its parts, boundaries, deep zones;
• to promote independent identification by students of the features of the deep zones of the ocean;

During the classes

Organizing time.

Learning new material.

Staged" Brief information about the oceans"

What is the World Ocean?

What parts does it consist of?

(From 4 oceans: Pacific, Atlantic, Indian and Arctic)

Today these oceans are our guests. (Students who are familiar with the "Oceans at a Glance" table on page 81 act as the oceans. They show the number plates and maximum depths on a physical map of the world.)

Student: -I - Pacific Ocean. My area is 180 million km, the average depth is

4028 m, and the maximum 11022 - the Mariana Trench).

(Similar to other oceans)

Student: - And all together we form the World Ocean (hold hands), the "Southern Ocean" runs up to them with the words: "I am the Southern Ocean, I am also part of the World Ocean."

Teacher: - Guys, how many oceans are there?

(Some scientists distinguish the Southern Ocean, but so far this controversial issue. So it counts as four for the time being.)

The teacher's story about the boundaries between oceans and seas using fig. 46 and maps of the oceans.

The boundaries between oceans are land masses.

Conditional boundaries.

The seas are marginal, inland and interisland.

(Students complete the activity on page 82)

Independent reading by students of the paragraph "Deep Zones of the World Ocean" and writing out in a notebook the definitions of concepts in bold.

Checking the completion of the task and showing bottom relief forms on the map of the oceans.

Anchoring

1) To consolidate, we use the headings "Let's check the knowledge", "And now more complex questions" on page 85

Name the oceans of the Earth.

(Pacific, Atlantic, Indian and Arctic)

Which ocean is the largest and which is the smallest?

(The Pacific Ocean is the largest and the Arctic Ocean is the smallest)

What is the sea?

(The sea is a part of the ocean, more or less isolated from it by land or elevations of underwater relief)

What are the boundaries between oceans?

(Where there is land between the oceans, this is an array of land, and where it is not, the boundaries are conventionally drawn along the meridians).

Name the deepest zones of the oceans.

(These are the continental shelf, the continental slope, the ocean floor and the deep-water trench).

What are the features of the layers of water at the bottom of the ocean?

(At the bottom of the ocean - ice water. The average temperature is about + 2 C)

Why is 80% of fish caught in the shelf zone?

(The water here is well warmed by the sun, there is a lot of oxygen, a large amount of organic matter serving as fish food)

Why are there no deep sea trenches in the Arctic Ocean?

(There are no zones of compression of the earth's crust as in other oceans).

2) Task on the contour map.

Mark the maximum depths of the oceans.

Homework: paragraph 10, assignment of the "Let's work with the map" section on page 85.

Behind the pages of a geography textbook.

Brief information from the history of ocean exploration.

There are several periods in the history of ocean exploration.

First period (7th-1st century BC - 5th century AD)

Reports are presented about the discoveries of the ancient Egyptians, Phoenicians, Romans and Greeks, who sailed the Mediterranean and Red Seas, went to the Atlantic and Indian Oceans.

Second period (5th-17th centuries)

In the early Middle Ages, some contribution to the study of the oceans was made by the Arabs, who sailed the Indian Ocean from the coast of East Africa to the Sunda Islands. In the 10-11 centuries. Scandinavians (Vikings) were the first Europeans to cross the Atlantic Ocean, discovering Greenland and the shores of Labrador. In the 15-16 centuries. Russian coast-dwellers mastered navigation on White Sea, went out to the Barents and Kara Seas, reached the mouth of the Ob. But sea voyages developed especially widely in the 15th-17th centuries. - during the period of great geographical discoveries. The voyages of the Portuguese (Bartolomeu Dias, Vasco da Gama), the Spaniards (Christopher Columbus, Ferdinand Magellan), the Dutch (Abel Tasman, etc.) important information about the ocean. The first information about the depths, about the currents of the World Ocean appeared on the maps. Information about the nature of the Arctic Ocean was accumulated as a result of searches for sea routes along the northern coasts of Eurasia and North America to East Asia. They were led by expeditions by Willem Barents, Henry Hudson, John Cabot, Semyon Dezhnev and others. In the middle of the 17th century, the accumulated information about individual parts of the World Ocean was systematized, and four oceans were identified.

Third period (18th-19th centuries)

Growing scientific interest in the nature of the oceans. In Russia, the participants of the Great Northern Expedition (1733-1742) studied the coastal parts of the Arctic Ocean.

The second half of the 18th century is the time of round-the-world expeditions. The most important was the voyage of James Cook and the Russian round-the-world expeditions, which only at the beginning of the 19th century. more than 40 were made. Expeditions led by I.F. Kruzenshtern and Yu.F. Lisyansky, F.F. Bellingshausen and M.P. Lazareva, V.I. Golovnina, S.O. Makarova and others collected extensive material on the nature of the World Ocean.

English expedition on the ship "Challenger" in 1872-1876. made a circumnavigation, collected material on the physical properties of ocean water, deep sediments at the bottom of the ocean, ocean currents.

The Arctic Ocean was explored by members of the Swedish-Russian expedition of A. Nordenskiöld on board the ship "Vega". F. Nansen's voyage was made on the Fram, which discovered a deep-water depression in the center of the Arctic Ocean. collected towards the end of the 19th century. the data made it possible to compile the first maps of the distribution of temperature and density of water at different depths, a scheme of water circulation, and bottom topography.

Fourth period (early 20th century)

Creation of specialized scientific maritime institutions that organized expeditionary oceanographic work. During this period, deep-sea trenches were discovered. Russian expeditions G.Ya. worked in the Arctic Ocean. Sedova, V.A. Rusanova, S.O. Makarov.

A special floating maritime institute was created in our country. First they explored the Arctic Ocean and its seas. In 1937, the first drifting station "North Pole" was organized (I.D. Papanin, E.E. Fedorov and others). In 1933-1940. the icebreaker "Sedov" was drifting near the Pole. A lot of new data on the nature of the central part of the Arctic Ocean has been obtained. The expedition on the icebreaking ship "Sibiryakov" in 1932 proved the possibility of sailing along the Northern Sea Route in one navigation.

New period (started in 50s)

In 1957-1959. The International Geophysical Year was held. Dozens of countries of the world participated in his work on the study of the nature of the Earth. Our country carried out research in the Pacific Ocean on board the Vityaz ship, expeditions worked in other oceans on the ships Akademik Kurchatov, Okean, Ob, and others. natural physical and geographical zonality of the World Ocean, the principles of its zoning have been developed. Much attention is paid to the study of the influence of the oceans on the formation of weather and its forecasting. The nature of tropical cyclones, the influence greenhouse effect to the change in the level of the Ocean, the quality aquatic environment and the factors influencing it. are being studied biological resources and the reasons that determine their productivity, forecasts of changes in the oceans are made in connection with the influence of human economic activity. Seabed surveys are underway.

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Environmental areas world ocean, ecological zones of the World Ocean, - areas (zones) of the oceans, where the systematic composition and distribution of morphological and physiological characteristics marine organisms are closely related to their environmental conditions: food resources, temperature, salt, light and gas regime of water masses, their other physical and chemical properties, physical and chemical properties of marine soils and, finally, with other organisms that inhabit the oceans and form biogeocenotic systems with them. All of these properties experience significant changes from surface layers to depths, from coasts to central parts ocean. In accordance with the indicated abiotic and biotic environmental factors, ecological zones are distinguished in the ocean, and organisms are divided into ecological groups.

All living organisms of the ocean as a whole are divided into benthos, plankton and nekton . The first group includes organisms living on the bottom in an attached or free-moving state. These are mostly large organisms, on the one hand, multicellular algae (phytobenthos), and on the other hand, various animals: mollusks, worms, crustaceans, echinoderms, sponges, coelenterates, etc. (zoobenthos). Plankton consists in most of the small plant (phytoplankton) and animal (zooplankton) organisms that are in suspension in the water and rush along with it, their organs of movement are weak. Nekton is a collection of animal organisms, usually large in size, with strong organs movement, - marine mammals, fish, cephalopods, squids. Besides these three environmental groups, we can distinguish pleuston and hyponeuston.

Playston- a set of organisms that exist in the very surface film of water, part of their body is immersed in water, and part is exposed above the surface of the water and acts as a sail. hyponeuston- organisms of the surface of the water layer of several centimeters, Each life form is characterized by certain form bodies and some adnexal formations. Nektonic organisms are characterized by a torpedo-shaped body shape, while planktonic organisms have adaptations for hovering (thorns and processes, as well as gas bubbles or drops of fat that reduce body weight), protective formations in the form of shells, skeletons, shells, etc.

The most important factor in the distribution of marine organisms is the distribution of food resources, both coming from the coast and created in the reservoir itself. According to the method of feeding, marine organisms can be divided into predators, herbivores, filter feeders - seston feeders (seston are small organisms suspended in water, organic detritus and mineral suspension), detritophages and soil eaters.

As in any other body of water, the living organisms of the ocean can be divided into producers, consumers (consumers) and decomposers (returners). The main mass of new organic matter is created by photosynthetic producers that can exist only in the upper zone, which is sufficiently well illuminated by sunlight and does not extend deeper than 200 m, but the main mass of plants is confined to the upper layer of water several tens of meters. Near the coasts, these are multicellular algae: macrophytes (green, brown and red), growing in a state attached to the bottom (fucus, kelp, alaria, sargasso, phyllophora, ulva, and many others), and some flowering plants (zostera phyllospadix, etc. .). Another mass of producers (unicellular planktonic algae, mainly diatoms and peridiniums) inhabits the surface layers of the sea in abundance. Consumers exist at the expense of ready-made organic substances created by producers. This is the whole mass of animals that inhabit the seas and oceans. Decomposers are the world of microorganisms that decompose organic compounds to the very simple shapes and again creating from these latter more complex compounds necessary for plant organisms for their vital activity. To some extent, microorganisms are also chemosynthetics - they produce organic matter by converting one chemical compound into another. This is how the cyclic processes of organic matter and life in sea waters take place.

According to the physical and chemical characteristics of the water mass of the ocean and the topography of the bottom, it is divided into several vertical zones, which are characterized by a certain composition and ecological features plant and animal population (see diagram). In the ocean and its constituent seas, two ecological areas are primarily distinguished: the water column - pelagial and the bottom benthal. Depending on the depth benthal divided by sublittoral zone - an area of ​​​​smooth decrease in land to a depth of about 200 m, bathyal– steep slope area and abyssal zone- the area of ​​the ocean floor with medium depth 3–6 km. Even deeper areas of the benthal, corresponding to the depressions of the ocean floor, are called ultraabyssal. The edge of the coast that is flooded at high tide is called littoral. Above the level of the tides, the part of the coast moistened by the splashes of the surf is called supralittoral.

Benthos lives in the uppermost horizon - in the littoral. Marine life and fauna abundantly populate the littoral zone and, in connection with this, develop a number of ecological adaptations to survive periodic drying. Some animals tightly close their houses and shells, others burrow into the ground, others hide under stones and algae or squeeze tightly into a ball and secrete mucus on the surface preventing drying. Some organisms get even higher than the uppermost line of the tide and are content with splashing waves that irrigate them. sea ​​water. This is the supralittoral zone. The littoral fauna includes almost all large groups animals: sponges, hydroids, worms, bryozoans, molluscs, crustaceans, echinoderms and even fish, some algae and crustaceans are selected in the supralittoral. Below the lowest ebb limit (to a depth of about 200 m), the sublittoral, or continental shelf, extends. In terms of the abundance of life, the littoral and sublittoral are in the first place, especially in temperate zone- huge thickets of macrophytes (fucuses and kelp), accumulations of mollusks, worms, crustaceans and echinoderms serve as abundant food for fish. The density of life in the littoral and sublittoral reaches several kilograms, and sometimes tens of kilograms, mainly due to algae, mollusks and worms. The sublittoral is the main area of ​​human use of the raw materials of the sea - algae, invertebrates and fish. Below the sublittoral there is a bathyal, or continental slope, passing at a depth of 2500-3000 m (according to other sources 2000 m) into the ocean floor, or abyssal, in turn, subdivided into upper abyssal (up to 3500 m) and lower abyssal (up to 6000 m) subzones . Within the bathyal, the density of life drops sharply to tens of grams and several grams per 1 m3, and in the abyssal to several hundred and even tens of mg per 1 l3. The largest part of the ocean floor is occupied by depths of 4000-6000 m. Deep-sea basins with their greatest depths up to 11000 m occupy only about 1% of the bottom area; this is the ultraabyssal zone. From the coasts to the greatest depths of the ocean, not only the density of life decreases, but also its diversity: many tens of thousands of species of plants and animals live in the surface zone of the ocean, and only a few dozen species of animals are known for the ultra-abyssal.

Pelagial also divided into vertical zones, corresponding in depth to benthal zones: epipelagial, bathypelagial, abyssopelagial. The lower boundary of the epipelagic zone (no more than 200 m) is determined by the penetration sunlight enough for photosynthesis. Organisms that live in the water column, or pelagial, are pelagos. Like benthic fauna, plankton density also experiences quantitative changes from coasts to the center, parts of the oceans, and from the surface to the depths. Along the coasts, the density of plankton is determined by hundreds of mg per liter, sometimes several grams, and in the middle parts of the oceans, by several tens of grams. In the depths of the ocean, it drops to a few mg or fractions of a mg per 1 m3. The flora and fauna of the ocean undergoes regular changes with increasing depth. Plants live only in the upper 200-meter water column. Coastal macrophytes, in their adaptation to the nature of lighting, experience a change in composition: the uppermost horizons are occupied mainly by green algae, then brown algae come in and red algae penetrate the deepest. This is due to the fact that in water the red rays of the spectrum decay the fastest, and blue and violet rays go deepest. Plants are painted in a complementary color, which provides best conditions photosynthesis. The same color change is observed in benthic animals: in the littoral and sublittoral they are predominantly gray and brown, and with depth, red color is more and more apparent, but the expediency of this color change in this case is different: coloring in an additional color makes them invisible and protects them from enemies. In pelagic organisms and in the epipelagic and deeper there is a loss of pigmentation, some animals, especially coelenterates, become transparent, like glass. In the most superficial layer of the sea, transparency facilitates the passage of sunlight through their body without harmful effects on their organs and tissues (especially in the tropics). In addition, the transparency of the body makes them invisible and saves them from enemies. Along with this, with depth, some planktonic organisms, especially crustaceans, acquire a red color, which makes them invisible in low light. Deep-sea fish do not obey this rule, most of them are painted black, although among them there are depigmented forms.

The earth's crust is continental and oceanic. The mainland is land and there are mountains, plains and lowlands on it - you can see them and you can always walk on them. But what is the oceanic crust like, we learn from the topic “Bottom of the oceans” (grade 6).

Exploring the ocean floor

The first who began to study the oceans were the British. On the warship "Challenger" under the command of George Nayes, they passed the entire water area of ​​the world and collected a lot of useful information, which scientists systematized for another 20 years. They measured the temperature of water, animals, but most importantly, they were the first to determine the structure of the ocean floor.

The device used to measure depth is called an echo sounder. It is located at the bottom of the ship and periodically sends out a signal so strong that it can reach the bottom, reflect and return to the surface. According to the laws of physics, sound in water moves at a speed of 1500 meters per second. Thus, if the sound returned in 4 seconds, then it reached the bottom already on the 2nd, and the depth in this place is 3000 m.

What does the earth look like underwater?

Scientists identify the main parts of the ocean floor:

• Underwater margin of the continents;
• transition zone;
• Ocean bed.

Rice. 1. Relief of the ocean floor

The mainland always partially goes under water, so the underwater margin is divided into the continental shelf and the continental slope. The phrase "go out to sea" means to leave the border of the continental shelf and the slope.

The continental shelf (shelf) is a part of the land submerged under water to a depth of 200 m. On the map, it is highlighted in pale blue or white. The largest shelf is in northern seas and in the Arctic Ocean. The smallest is in North and South America.

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The continental shelf warms up well, so this is the main area for resorts, farms for the extraction and cultivation of seafood. Oil is produced in this part of the ocean

The continental slope forms the boundaries of the oceans. The continental slope is considered from the edge of the shelf to a depth of 2 kilometers. If the slope were on land, then it would be a high cliff with very steep, almost straight slopes. But besides their steepness, there is another danger lurking in them - oceanic trenches. These are narrow gorges that go under water for thousands of meters. The largest and most famous trench is the Mariana Trench.

Ocean bed

Where the continental ledge ends, the ocean bed begins. This is its main part, where there are deep-water basins (4 - 7 thousand meters) and hills. The ocean bed is located at a depth of 2 to 6 km. Animal world it is very poorly represented, since in this part there is practically no light and it is very cold.

Rice. 2. Image of the ocean floor

The most important place is occupied by the mid-ocean ridges. They are a large mountain system, like on land, only under water, stretching along the entire ocean. The total length of the ranges is about 70,000 km. They have their own complex structure: gorges and deep slopes.

Ridges form at the junctions of lithospheric plates and are sources of volcanoes and earthquakes. Some islands are very interesting origin. In those places where volcanic rock accumulated and eventually came to the surface, the island of Iceland was formed. That is why there are many geysers and hot springs, and the country itself is a unique nature reserve.

Rice. 3. Relief of the Atlantic Ocean

ocean floor

The soil of the ocean is marine sediment. They are of two types: continental and oceanic. The first ones formed from land: pebbles, sand, other particles from the shore. The second is bottom sediments formed by the ocean. These are leftovers marine life, volcanic ash.

What have we learned?

The structure of the ocean floor is very uneven. There are three main parts of it: the continental margin (divided into the continental shelf and slope), the transition zone and the ocean floor. It was in its central part that an amazing relief was formed - a mid-ocean ridge, representing a single mountain system encircling almost the entire Earth.

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