Chapter 5 -
The sea and the ocean
1. Answer the following questions:
(a) What are the causes of ocean currents?
Answer: Ocean currents are caused by the Earth's rotation, constant winds, water temperature, salinity and pressure, and the size of the coastline.
(b) What is meant by hot water flow?
Answer: The water in the cold regions becomes cold, compact and heavy. Therefore, warm and thin seawater flows upwards from the tropics to the cold as surface currents. This is the flow of hot water.
(c) How many types of marine life are there? On what basis are they classified?
Answer: There are three types of marine organisms: plankton, benthos and nectons. Marine organisms have been divided into classes based on their movement patterns and habitats.
(d) In what areas of the sea are fisheries usually established?
Answer: Fisheries are formed in areas of the sea where plankton plants are abundant.
2. 2. Give reasons—
(a) Scarcity tides are not as strong as spring tides.
Answer: On full moons and new moons, the Moon, Earth, and Sun fall almost in the same line. During these two days, the spring tides rise higher due to the attraction of both the Moon and the Sun. As a result, it becomes stronger.
(b) Nowadays, seafood can be bought everywhere in the world.
Answer: Marine fish are in demand everywhere in the world. They are stored in tins and after identification are shipped to various distant countries with refrigeration. So nowadays, seafood is available to purchase everywhere in the world.
(c) Tsunamis occur frequently in Japan.
Answer: Japan is located in the Pacific volcanic belt. This belt is the most prone to earthquakes in the world. So Japan has frequent earthquakes that trigger tsunamis.
(d) Despite its large size, the Sun has low tidal power.
Answer: The Sun is 27 million times larger than the Moon; The distance from the Earth to the Moon is 3,844,400 km. The Sun is at a distance of 149,600,000 km from the Earth. Therefore, the creative energy of the Sun's movement is low.
(e) Shipping is excellent for foreign trade.
Answer: Shipping is the most reliable means of foreign trade. Because it is free and even all around, waterways do not have some of the obstacles that exist on land.
3. 3. In the correct answer ☑ With Chin-
(1) Cooling water currents usually originate from—
(a) In the polar region (b) In the equatorial region (c) None.
Answer: In the polar regions.
(2) Sea level fluctuations twice a day –
(a) Ocean currents (b) Tides (c) Waves.
Answer: The tides.
(3) The term tsunami means—
(a) Earthquakes (b) Sea waves (c) Harbor waves.
Answer: The waves of the harbor.
(4) Marine animals that can swim—
(a) Necton (b) Benthose (c) Plankton
Answer: Benth's.
(4) Matching right with left-
Answer:
