Chapter 8 Biology Class 9 Notes
Important Notes of Chapter No.8: Nutrition Chapter 8 Biology Class 9 Notes written by Honorable Sir Adnan Haider Suib. These notes are very helpful in the preparation of Chapter 8 Biology Class 9 Notes for students of the 9th class Biology Urdu Medium and these are according to the paper patterns of all Punjab boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Very Important Multiple Choice Questions (MCQs) of Chapter No.8: Nutrition Urdu Medium.
- The process in which food is obtained or prepared, absorbed and converted into body substances
for growth and energy, is called nutrition. Nutrients are the elements and compounds that an
organism obtains and uses for energy or for the synthesis of new materials.
- We know that autotrophic organisms obtain water, carbon dioxide and minerals from their
environment and prepare their food which is then used for growth and energy. On the other hand
heterotrophic organisms obtain their food from other organisms and use it for growth and energy.
- MINERAL NUTRITION IN PLANTS: Plants have the most efficient mechanisms for autotrophic mode of nutrition. Plants get carbon,
hydrogen and oxygen from carbon dioxide and water. In addition to these elements, plants
also require mineral elements for various activities and structures. The nutrients which are
required in large quantities are called macronutrients e.g. carbon, hydrogen, oxygen, nitrogen,
magnesium, potassium etc. Similarly, the nutrients which are required in small quantities are called
micronutrients e.g. iron, molybdenum, boron, chlorine, zinc etc. If any of these nutrients is not
available to plant, they show abnormalities and do not grow normally. Table 8.1 describes the roles
of important macro and micronutrients in plants.
- Roles of Nitrogen and Magnesium: Plants get nitrogen in the form of nitrates. Nitrogen is a major component of proteins, hormones,
chlorophyll, vitamins and enzymes essential for plant life. Nitrogen metabolism is a major factor in
stem and leaf growth. Too much nitrogen can delay flowering and fruiting. Deficiencies of nitrogen
can reduce yields, cause yellowing of the leaves and stunt growth.
- Magnesium is a structural component of chlorophyll. It is also necessary for the functioning of
plant enzymes to produce carbohydrates, sugars and fats. It is used for fruit and nut formation and
essential for germination of seeds. Deficiency of magnesium causes yellowing and wilting of leaves.
- IMPORTANCE OF FERTILIZERS: As humans cultivated plants, it was learned that addition of certain materials to soil sometimes
resulted in plants with desirable characteristics (e.g., more fruit, faster growth, more attractive
flowers). Such materials were named as fertilizers. Fertilizers are broadly classified as organic or
inorganic.
- Naturally occurring inorganic fertilizers include rock phosphate, elemental sulfur and gypsum. These
are not chemically modified. If nitrogen is the main element, they are called nitrogen fertilizers. Most
inorganic fertilizers dissolve readily in water and are immediately available to plants for uptake.
- Environmental hazards related to fertilizer's use: The massive quantities of inorganic fertilizers affect the soil nutrient-holding capacity. Their high
solubilities also degrade ecosystems through eutrophication (increase in chemical nutrients in
an ecosystem). Storage and application of some nitrogen fertilizers may cause emissions of the
greenhouse gas nitrous oxide. Ammonia gas may be emitted from the inorganic fertilizers. This
extra ammonia can also increase soil acidity. Excessive nitrogen fertilizers can lead to pest problems
by increasing their reproduction rate.
- For these reasons, it is recommended that the nutrient content of the soil and nutrient requirements
of the crop should be calculated before the application of inorganic fertilizers.
Excessive amounts of organic fertilizers cause environmental problems due to nitrate leaching or
run off of soluble organic compounds.
- COMPONENTS OF HUMAN FOOD: The nutritional requirements of human and other animals are relatively complex as compared to
plants. Like other animals, the nutrients used by humans include carbohydrates, lipids, nucleic
acids, proteins, minerals, vitamins. Besides these nutrients, they also require water.