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Q1. Nutrients are Essential Components of Food
Description
The correct answer is Nutrients. Nutrients are the useful substances present in food that help our body grow, stay healthy, and get energy. Without nutrients, the body cannot perform important functions properly.
Different nutrients perform different jobs in the body. Some nutrients provide energy, some help in body building, and others protect us from diseases.
Main Types of Nutrients
- Carbohydrates
- Proteins
- Fats
- Vitamins
- Minerals
- Water
- Roughage
Easy Explanation
Just like a vehicle needs fuel to run properly, the human body needs nutrients to work efficiently. Nutrients help us walk, think, play, grow, and remain healthy.
Functions of Important Nutrients
- Carbohydrates
Provide energy to the body. - Proteins
Help in growth and repair of body tissues. - Fats
Store energy and keep the body warm. - Vitamins
Protect the body from diseases. - Minerals
Help in bone formation and proper body functioning.
Step-by-Step Understanding
Step 1: We eat food daily.
Step 2: Food contains useful substances.
Step 3: These substances are called nutrients.
Step 4: Nutrients help in growth and energy production.
Step 5: The body uses nutrients for healthy functioning.
Examples
- Rice and bread provide carbohydrates.
- Milk and pulses provide proteins.
Key Points
- Nutrients are essential for life.
- They provide energy and growth.
- Vitamins and minerals protect health.
- Balanced diet contains all nutrients.
- Lack of nutrients causes diseases.
Q2. Leaves are the Food Factory of Plants
Description
The correct answer is Leaves. Leaves are called the food factory of plants because they prepare food through the process of photosynthesis.
Plants make their own food using sunlight, water, carbon dioxide, and chlorophyll. This process mainly takes place in the leaves.
Photosynthesis Process
Carbon dioxide + Water + Sunlight → Glucose + Oxygen
Why Leaves are Called Food Factory
Leaves contain chlorophyll, a green pigment that traps sunlight. Tiny pores called stomata help in gas exchange. Water absorbed by roots reaches the leaves, and food is prepared there.
Easy Explanation
Plants cannot move around to search for food like animals. Therefore, they prepare food by themselves using sunlight. Leaves perform this important work, so they are known as the food factory of plants.
Step-by-Step Understanding
Step 1: Roots absorb water from soil.
Step 2: Leaves take carbon dioxide from air.
Step 3: Chlorophyll captures sunlight.
Step 4: Photosynthesis takes place.
Step 5: Food is prepared and stored.
Importance of Photosynthesis
- Produces oxygen.
- Provides food for plants.
- Supports life on Earth.
- Maintains balance of gases.
Examples
- Green leaves of mango tree.
- Spinach leaves preparing food.
Key Points
- Leaves perform photosynthesis.
- Chlorophyll helps trap sunlight.
- Plants prepare their own food.
- Oxygen is released during photosynthesis.
- Leaves are called food factories.
Q3. Lichen is a Symbiotic Relationship Between Algae and Fungus
Description
The correct answer is Algae and Fungus. Lichen is an example of symbiosis, where two organisms live together and help each other.
In lichen:
- Algae prepare food by photosynthesis.
- Fungus provides water, minerals, and protection.
Both organisms benefit from each other, so this relationship is called mutual symbiosis.
Easy Explanation
Algae can make food but cannot store enough water. Fungus can absorb water but cannot make food. Together they support each other and survive in difficult conditions.
Step-by-Step Understanding
Step 1: Algae perform photosynthesis.
Step 2: Food is prepared for both organisms.
Step 3: Fungus absorbs water and minerals.
Step 4: Fungus protects algae from drying.
Step 5: Both organisms survive together.
Importance of Lichen
- Grow on rocks and tree bark.
- Help in soil formation.
- Indicators of air pollution.
Why Lichens are Pollution Indicators
Lichens are sensitive to polluted air. They grow well only in clean environments. Their absence often indicates air pollution.
Examples
- Lichens on tree bark.
- Lichens growing on rocks in hilly areas.
Key Points
- Lichen = Algae + Fungus.
- Example of symbiosis.
- Algae prepare food.
- Fungus provides protection and water.
- Sensitive to air pollution.
Q4. Sun is the Ultimate Source of Energy
Description
The correct answer is Solar energy/Sun. The Sun is the ultimate source of energy for almost all living organisms on Earth.
Plants use sunlight to prepare food through photosynthesis. Animals depend directly or indirectly on plants for food. Therefore, most forms of energy on Earth originate from the Sun.
Easy Explanation
Without sunlight, plants cannot make food. Without plants, animals and humans cannot survive. This is why the Sun is considered the main source of energy for life.
How Energy Flows in Nature
Sun → Plants → Animals → Humans
Step-by-Step Understanding
Step 1: Sun provides light and heat.
Step 2: Plants absorb sunlight.
Step 3: Plants prepare food through photosynthesis.
Step 4: Animals eat plants.
Step 5: Humans get energy from plants and animals.
Other Energy Sources Linked to Sun
- Wind Energy
Caused by uneven heating of Earth by Sun. - Water Energy
Water cycle depends on solar heat. - Fossil Fuels
Formed from ancient plants and organisms that depended on sunlight.
Importance of Sun
- Supports photosynthesis.
- Maintains temperature of Earth.
- Helps water cycle.
- Essential for survival of life.
Examples
- Plants using sunlight to make food.
- Solar panels producing electricity.
Key Points
- Sun is the main energy source.
- Plants depend on sunlight.
- Animals depend on plants.
- Wind and water energy are indirectly solar-based.
- Life on Earth depends on Sun.
Q5. Rhizobium Bacteria Provide Nitrogen to Plants
Description
The correct answer is Nitrogen. Rhizobium is a useful bacterium that lives in the root nodules of leguminous plants such as pea, gram, and beans.
Rhizobium converts atmospheric nitrogen into usable forms for plants. This process is called nitrogen fixation.
Why Nitrogen is Important
Nitrogen is necessary for:
- Plant growth
- Protein formation
- Healthy leaves
- Crop production
Plants cannot directly use nitrogen gas from the atmosphere. Rhizobium helps convert it into compounds plants can absorb.
Easy Explanation
The atmosphere contains a large amount of nitrogen gas, but plants cannot use it directly. Rhizobium bacteria change this nitrogen into useful substances and provide them to plants.
Step-by-Step Understanding
Step 1: Rhizobium lives in root nodules.
Step 2: It absorbs atmospheric nitrogen.
Step 3: Nitrogen is converted into useful compounds.
Step 4: Plants absorb these compounds.
Step 5: Plants grow healthier and greener.
Symbiotic Relationship
Plants provide food and shelter to Rhizobium.
Rhizobium provides nitrogen to plants.
Both benefit from each other.
Examples
- Rhizobium in pea plants.
- Rhizobium in bean roots.
Key Points
- Rhizobium fixes atmospheric nitrogen.
- Lives in root nodules of leguminous plants.
- Helps plant growth.
- Example of symbiosis.
- Improves soil fertility.
Quick Revision Notes
Nutrients
- Essential components of food.
- Help in growth and energy.
- Include proteins, carbohydrates, vitamins, and minerals.
Leaves
- Called food factory of plants.
- Perform photosynthesis.
- Release oxygen.
Lichen
- Combination of algae and fungus.
- Example of symbiosis.
- Indicates clean air.
Sun
- Ultimate source of energy.
- Supports life on Earth.
- Helps plants prepare food.
Rhizobium
- Nitrogen-fixing bacteria.
- Lives in root nodules.
- Improves plant growth and soil fertility.