Hello students, in this blog you can find important summary notes from the Chapter 1, Science , NCERT Book of Class 8. These notes can be used for preparation of various school Competitive Exams, Olympiads and also developing strong Fundamentals.
1. Energy from the food is utilised by organisms for carrying out their various body functions, such as digestion, respiration and excretion.
2. In order to provide food for a large population – regular production, proper management and distribution is necessary.
3. Crop : When plants of the same kind are cultivated at one place on a large scale, it is called a crop.
4. Crops are classified on the basis of the season in which they grow.
5. Different types of crops :
6. Two broad cropping patterns :
– Kharif Crops :
The crops which are sown in the rainy season (June to September) are called kharif crops.
Examples : paddy, maize, soyabean, groundnut and cotton.
– Rabi Crops : The crops grown in the winter season (October to March) are called rabi crops.
Examples : wheat, gram, pea, mustard and linseed.
– Crops like pulses and vegetables are grown during summer at many places.
7. Paddy requires a lot of water, therefore, it is grown only in the rainy season.
8. Agricultural practices :
– Preparation of soil
– Adding manure and fertilisers
– Protecting from weeds
9. Turning and loosening of soil is very important for cultivation of crops because :
– this allows the roots to penetrate deep into the soil.
– helps in the growth of earthworms and microbes present in the soil, which further loosen the soil and add humus to it.
– to absorb various nutrients from the dead organisms that are released back into the soil
– it brings the nutrient-rich soil to the top, so that plants can use these nutrients.
10. Tilling or Ploughing : The process of loosening and turning of the soil is called tilling or ploughing.
11. Crumbs : The ploughed field may have big clumps of soil called crumbs.
12. The main tools for breaking crumbs are : plough, hoe and cultivator.
13. Plough benefits by :
– adding fertilisers to the crop,
– removing the weeds and
– turning the soil.
14. Ploughshare : The plough contains a strong triangular iron strip called ploughshare.
15. Ploughshaft : The main part of the plough is a long log of wood which is called a ploughshaft.
16. Hoe : It is a simple tool which is used for removing weeds and for loosening the soil.
17. Cultivator : Nowadays ploughing is done by tractor-driven cultivator.
18. Damaged seeds become hollow and are thus lighter and hence, they float on water.
19. Seed drill : Nowadays the seed drill is used for sowing with the help of tractors.
20. Advantages of seed drill :
– it sows the seeds uniformly at equal distance and depth. – it ensures that seeds get covered by the soil after sowing, thus
protecting from being eaten by birds
– it saves time and labour.
21. Seeds of a few plants such as paddy are first grown in a nursery and later when they grow into seedlings, they are transplanted to the field.
22. Appropriate distance between the seeds is necessary to avoid overcrowding of plants.
23. Manure and Fertilisers : The substances which are added to the soil in the form of nutrients for the healthy growth of plants are called manure and fertilisers.
24. The continuous cultivation of crops makes the soil poor in nutrients.
25. Manuring : Farmers have to add manure to the fields to replenish the soil with nutrients, this process is called as manuring.
26. Manure is an organic substance obtained from the decomposition of plant or animal wastes.
27. Fertilisers : They are chemicals which are rich in a particular nutrient, and produced in factories.
Examples : urea, ammonium sulphate, super phosphate, potash, NPK (Nitrogen, Phosphorus, Potassium).
28. To maintain fertility of soil we have to :
– substitute fertilisers with organic manure
– leave the field uncultivated (fallow) in between two crops.
29. Methods to replenish soil with nutrients :
– use of manure, because this improves soil texture as well as its water retaining capacity
– through crop rotation, that can be done by growing different crops alternately
30. Rhizobium bacteria, present in the nodules of roots of leguminous plants fix atmospheric nitrogen.
31. Advantages of manure over fertilizers :
– it enhances the water holding capacity of the soil.
– it makes the soil porous due to which exchange of gases becomes easy. – it increases the number of friendly microbes.
– it improves the texture of the soil.
32. Plants contain nearly 90% water.
33. Irrigation : The supply of water to crops at regular intervals is called irrigation.
34. Water is essential for plants because :
– germination of seeds does not take place under dry conditions
– nutrients dissolved in water are transported to each part of the plant.
– water protects the crop from both frost and hot air currents.
– to maintain the moisture of the soil for healthy crop growth, fields have to be watered regularly.
35. In summer, the frequency of watering is higher, because of the increased rate of evaporation of water from the soil and the leaves.
36. Sources of irrigation :
37. Traditional Methods of Irrigation
– moat (pulley -system)
– chain pump
– rahat (Lever system)
38. Modern Methods of Irrigation :
– Sprinkler System
– Drip system
39. Sprinkler System :
– It is more useful on the uneven land where sufficient water is not available.
– Here water is allowed to flow through the main pipe under pressure with the help of a pump, where it escapes from the rotating
nozzles on perpendicular pipes.
– Water gets sprinkled on the crop as if it is raining.
– Sprinkler is very useful for lawns, coffee plantation and several other crops.
40. Drip system :
– In this system, the water falls drop by drop directly near the roots, hence called drip system.
– It is the best technique for watering fruit plants, gardens and trees.
– Water is not wasted at all, hence it is a boon in regions where availability of water is poor.
41. Weeds : In a field many other undesirable plants may grow naturally along with the crop. These undesirable plants are called weeds.
42. The removal of weeds is called weeding.
43. Weeding is necessary since :
– Weeds compete with the crop plants for water, nutrients, space and light thus they affect the growth of the crop
– Some weeds interfere even in harvesting and may be poisonous for animals and human beings.
44. Tilling before sowing of crops helps in uprooting and killing of weeds.
45. Weedicides : Weeds are also controlled by using certain chemicals, called weedicides,
46. Harvesting : The cutting of crop after it is mature is called harvesting.
47. Harvester : Harvesting is either done manually by sickle or by a machine called harvester.
48. Threshing : In the harvested crop, the grain seeds need to be separated from the chaff. This process is called threshing.
49. Combine : Threshing is carried out with the help of a machine called combine which is in fact a harvester as well as a thresher.
50. Winnowing : Farmers with small holdings of land do the separation of grain and chaff by winnowing.
51. Special festivals associated with the harvest season are Pongal , Baisakhi, Holi, Diwali, Nabanya and Bihu.
52. Before storing the grains are properly dried in the sun because:
– Harvested grains have more moisture.
– If freshly harvested grains (seeds) are stored without drying, they may get spoilt or attacked by organisms, making them unfit for
use or for germination.
– This prevents the attack by insect pests, bacteria and fungi.
53. Large scale storage of grains is done in silos and granaries to protect them from pests like rats and insects.
54. Animal Husbandry : Animals reared at home or in farms, have to be provided with proper food, shelter and care. When this is done on
a large scale, it is called animal husbandry.
55. We get cod liver oil from fish which is rich in vitamin D.