CBSE Class 9 Science Notes: Improvement in Food Resources

🌾 Plant Breeding and Selection for Better Yield

Plant breeding is the art and science of improving the genetic makeup of plants to produce desired traits. The goal is to enhance crop productivity, nutritional value, and resistance to environmental stresses. Selection involves choosing the best performing plants and using them to produce the next generation.

Core Concepts:

• Selection: Choosing plants with desirable traits (e.g., higher yield, disease resistance).
• Hybridization: Cross-breeding different varieties or species to combine desirable traits.
• Genetically Modified Crops (GMOs): Plants with DNA altered for enhanced features (e.g., pest resistance).

Steps Involved:

1. Collection of Variability: Gathering diverse plant varieties.
2. Evaluation and Selection of Parents: Identifying plants with desired traits.
3. Cross-Hybridization: Combining traits through cross-pollination.
4. Selection and Testing: Selecting superior offspring.
5. Release and Commercialization: Making improved varieties available to farmers.

Examples:

• High-Yielding Varieties: Improved wheat and rice varieties.
• Disease-Resistant Crops: Crops bred to resist specific pathogens.
• Nutritionally Enhanced Crops: Varieties with increased vitamin or protein content (e.g., golden rice).

🐄 Animal Breeding for Quality Improvement

Animal breeding focuses on improving the quality and productivity of livestock, poultry, and other animals. This involves selecting animals with desirable traits and breeding them to improve the characteristics of the offspring.

Core Principles:

• Selection: Choosing animals with desirable traits (e.g., high milk yield, meat quality).
• Cross-breeding: Breeding different breeds to combine beneficial traits.
• Artificial Insemination: Introducing semen without natural mating, enhancing genetic improvement.

Types of Breeding:

• Inbreeding: Breeding between closely related individuals (can lead to uniformity but also increase the risk of genetic defects).
• Outbreeding: Breeding between unrelated individuals (improves vigour and genetic diversity).
• Cross-breeding: Breeding between different breeds (combines desirable traits of each breed).
• Outcrossing: Breeding between animals of the same breed but not closely related.

Examples:

• Improved Dairy Cattle: High-yielding breeds like Holstein Friesian.
• Enhanced Poultry: Breeds for increased egg production or meat quality.
• Better Meat Animals: Breeds of sheep, goats, and pigs for improved meat characteristics.

🌿 Use of Manures and Fertilizers

Manures and fertilizers are essential for enriching the soil and providing nutrients needed for plant growth. They replenish the soil, increase yields, and ensure healthy crops.

Definitions:

• Manures: Organic substances derived from the decomposition of plant and animal waste.
• Fertilizers: Inorganic substances containing essential plant nutrients.

Types of Manures:

• Compost: Prepared by decaying plant and animal residues.
• Vermicompost: Compost made with the aid of earthworms.
• Green manure: Using plants to produce manure before sowing of the main crop.

Types of Fertilizers:

• Nitrogenous Fertilizers: Provide nitrogen (e.g., urea).
• Phosphatic Fertilizers: Provide phosphorus (e.g., superphosphate).
• Potassic Fertilizers: Provide potassium (e.g., potassium chloride).
• NPK Fertilizers: Contain a mixture of nitrogen, phosphorus, and potassium.

Important Note: Excessive use of chemical fertilizers can pollute soil and water.

🛡️ Protection from Pests and Diseases

Protecting crops from pests and diseases is vital for maximizing yields and minimizing economic losses. This includes prevention, identification, and control methods.

Methods of Control:

• Crop Rotation: Changing the crops grown in a field to disrupt pest and disease cycles.
• Use of Resistant Varieties: Planting crop varieties that are naturally resistant to pests and diseases.
• Pest Control: Use of pesticides to kill or control pests and herbicides to kill weeds.
• Biological Control: Using natural enemies of pests (e.g., predators, parasites).

Examples:

• Pesticides: Insecticides, herbicides, and fungicides.
• Biological Control Agents: Use of ladybugs to control aphids.
• Integrated Pest Management (IPM): Combining multiple control methods.

🌱 Introduction to Organic Farming

Organic farming is a sustainable agricultural system that avoids the use of synthetic fertilizers, pesticides, and genetically modified organisms (GMOs). It focuses on ecological balance and soil health.

Core Principles:

• Soil Health: Improving soil fertility through composting, green manuring, and crop rotation.
• Biodiversity: Promoting diverse ecosystems to control pests and diseases.
• Natural Pest Control: Using biological control agents and other natural methods.
• No Synthetic Chemicals: Avoiding synthetic fertilizers and pesticides.

Advantages:

• Environmentally Friendly: Reduces pollution and promotes sustainability.
• Healthy Food: Produces food free from synthetic chemicals.
• Improved Soil Health: Enhances soil fertility and structure.
• Reduced Risk: Minimizes exposure to harmful chemicals for farmers.

Disadvantages:

• Lower Yields: Often lower yields compared to conventional farming.
• Higher Costs: Organic farming can be more labor-intensive and expensive.
• Pest and Disease Control: Can be more difficult to control pests and diseases.