General Science Solutions Solutions for Class 7 Science Chapter 16 - Natural Resources

Answer:

• prevent soil erosion
• control floods
• reduce the rate of evaporation
• maintain balance of atmospheric gases
• protect wildlife
• help percolation of water into the ground
• reduce the velocity of wind
• provide food and shelter to various kinds of animals
• provide us with wood, essential oils, gums, fruits etc.

c. Ocean resources: Oceans are also important resources and this can be understood by the fact that they cover greater part of earth's surface than land itself. The resources which can be obtained from oceans can be of two types- 

Mineral resources- Most of the minerals are obtained from oceans, for example, thorium (used in atomic energy production), magnesium (used in flash bulb of camera), sodium (used in production of cloth and paper. 

Bio resources- Examples of bio resources from oceans include fishes, shells, fungi, shark and cod fish, sea cucumbers etc.

Answer:

a. Fuel that is obtained from fossils such as dead sea organisms, dead plants and animals, etc is known as fossil fuel. The different types of fossil fuels are:

• Coal- Also known as black gold, it is black in colour. It is as hard as stone and on burning, it releases a lot of energy. 
• Petroleum: Also known as mineral oil, it is used in obtaining various other substances like gasoline, diesel, kerosene etc.
• Natural gas: Found in association with petroleum and is ued in the forms of CNG and LNG.

b. Components which can be obtained from mineral oil are:

• petroleum
• aviation petrol
• gasoline
• diesel
• kerosene
• naptha
• lubricating oil
• tar
• also used in the production of dyes, pesticides etc.

c. Forests provide numerous products to man.

• The fruits and tubers from the forests are a source of nutritive food.
• The timber is used in various industries and in everyday human use like furniture.
• Herbs from forests are used as medicine.
• The leaves of certain trees are used in making disposable plates.
• The raisin from the trees is used for manufacturing gum.

d.  Oceans are also important resources and this can be understood by the fact that they cover greater part of earth's surface than land itself. The resources which can be obtained from oceans can be of two types- 


e. Coal and petroleum were formed from the degradation of biomass millions of years ago. The reserves of these resources are limited and they take a very long time to form. If these are not used judiciously, they will soon get exhausted.


f. The diversity of plants and animals is declining in the forests because of several reasons. These reasons can be summed up in the following factors:
 

• Habitat loss and fragmentation: This is the major cause for loss of biodiversity. Habitat destruction is caused by human activities such as deforestation and increasing pollution, leading to the loss of many plants and animals. Habitat fragmentation is the breaking up of habitat of a particular species into fragments.

• Over-exploitation: Humans, because of their greed and increased exploitation of natural resources, have contributed to the endangerment of commercially important species of plants and animals. Species such as the Steller’s sea cow and passenger pigeons have become extinct as a result of over-exploitation by humans.

• Alien-species invasion: The unintentional or deliberate introduction of alien species causes a decline in the number of indigenous species. Alien species prove invasive and affect the survival of native species in a grave manner. Also, sometimes they compete with native species that eventually leads to their destruction. For example, the Nile perch, introduced in Lake Victoria, led to the extinction of more than 200 species of cichlid fish in the lake.

• Co-extinction: When plants or animals become extinct, other plants or animals that are dependant on it in an obligatory way also become extinct.

g. Minerals are naturally occurring solid substances that have a characteristic internal structure and properties. They are formed through geological processes that take millions of years. Examples of minerals are:

1. Iron ore: farming implements, rails of railway track
2. Manganese: medicines, electrical appliances
3. Bauxite: aeroplanes, transport vehicles, electric wires
4. Copper: radios, telephones, vehicles, kitchen utensils, statues
5. Mica: ayurvedic medicines, dyes, electric machines and equipments, wireless communication equipments.


h. The two important stages in the process of obtaining metals from ore are extraction and concentration.

Answer:

The following steps are taken/can be taken to conserve natural resources like:

Conservation of minerals:

• Improving the technology to allow use of low grade ores at low costs.
• Recycling of metals.
• Using scrap metals and other substitutes.
• Using the available minerals in a planned manner.

Conservation of forests:

Answer:

Answer:

The economic condition of a nation depends on its natural resources and it can be explained from the following example of coal and petroleum. Natural resources such as coal, petroleum and natural gas are engines of growth of a country. All the industrial projects are undertaken on the basis of the energy provided by these natural resources. They provide electricity to industrial establishments and households in the country. They are the only source of fuel for propelling vehicles, railways and air transport. They are used as fuel for cooking food. A country’s survival and development largely depends on these natural resources. 

Answer:

The following medicinal plants can be grown in the school as they are easily available, easy to maintain and have various health benefits:​

• Cinchona − Quinine, a drug used in the treatment of malaria, is obtained from the bark of the Cinchona tree.
• Eucalyptus − The leaves of eucalyptus are used for extracting on oil which is used in the treatment of blocked nose and throat infections. It is also used as a mosquito repellent.
• Neem - The leaves and stems can be used in the treatment of fever, cold or for oral hygiene.
• Cinnamon - It can be used in the treatment of diarrhoea and nausea.