Delve into Chapter 9: Physiology from the Class 9th Biology New Syllabus, tailored for Lahore and Punjab Boards. This detailed post covers the human organ systems, their physiological functions, and related concepts, including the nervous system, circulatory system, and respiration. Includes solved MCQs, short questions, and exam tips to ensure success in your exams. A must-read for Class 9 students preparing for Punjab board exams.
1. Which of the following plant nutrients is required in large amounts?
Options:
a) Iron
b) Potassium
c) Phosphorus
d) Boron
Answer: b) Potassium
Explanation: Potassium is a macronutrient essential for plant growth. It regulates water uptake, photosynthesis, and enzyme activation.
Tip: Macronutrients like potassium, nitrogen, and phosphorus are needed in large amounts, while micronutrients like boron and iron are required in smaller amounts.
2. Which element is required by plants for the formation of chlorophyll?
Options:
a) Phosphorus
b) Calcium
c) Magnesium
d) Sulphur
Answer: c) Magnesium
Explanation: Magnesium is a core element in chlorophyll, enabling photosynthesis by capturing sunlight.
Tip: Link magnesium to chlorophyll by remembering that green leafy vegetables are rich in magnesium.
3. The primary function of root hairs is:
Options:
a) Transport of nutrients
b) Storage of food
c) Increase surface area for absorption
d) Synthesis of proteins
Answer: c) Increase surface area for absorption
Explanation: Root hairs increase the surface area, making water and nutrient uptake from the soil more efficient.
Tip: Think of root hairs as “extensions” that maximize absorption.
4. Root hairs absorb salts from soil by:
Options:
a) Diffusion
b) Active transport
c) Filtration
d) Osmosis
Answer: b) Active transport
Explanation: Active transport uses energy (ATP) to move salts and nutrients from lower to higher concentrations in the roots.
Tip: Remember, “active” means energy is required.
5. Water moves from the soil into root cells by:
Options:
a) Osmosis
b) Facilitated diffusion
c) Active transport
d) Bulk flow
Answer: a) Osmosis
Explanation: Osmosis is the movement of water from high to low water potential across a semi-permeable membrane.
Tip: Water = Osmosis; nutrients = Active transport.
6. The transpiration is regulated by:
Options:
a) Mesophyll
b) Guard cells
c) Xylem
d) Phloem
Answer: b) Guard cells
Explanation: Guard cells control the opening and closing of stomata, regulating water loss through transpiration.
Tip: Link “guard” cells with “guarding” the stomata.
7. Under which condition will there be high rate of transpiration?
Options:
a) High humidity
b) Low light intensity
c) Wind
d) Waterlogged soil
Answer: c) Wind
Explanation: Wind removes water vapor around leaves, increasing the rate of transpiration.
Tip: Think of wind as a “dryer” increasing water loss.
8. Which ion plays a role in the opening of stomata?
Options:
a) Sodium (Na⁺)
b) Potassium (K⁺)
c) Calcium (Ca²⁺)
d) Magnesium (Mg²⁺)
Answer: b) Potassium (K⁺)
Explanation: Potassium ions regulate the turgor pressure in guard cells, causing stomata to open or close.
Tip: Associate potassium (K⁺) with “Key” for stomata.
9. In most plants, the food is transported in the form of:
Options:
a) Glucose
b) Sucrose
c) Starch
d) Maltose
Answer: b) Sucrose
Explanation: Sucrose is water-soluble and easily transported through the phloem.
Tip: Glucose is stored, sucrose is transported.
10. What is TRUE according to the pressure flow mechanism of food transport?
Options:
a) Water enters the source, creating pressure.
b) Water is pulled from the sink.
c) Movement of food in phloem is due to gravity.
d) Solutes move from low to high concentration.
Answer: a) Water enters the source, creating pressure.
Explanation: In the source (e.g., leaves), sugar concentration draws water in, creating pressure that pushes food through the phloem to the sink (e.g., roots).
Tip: Think of the source as the “pump” for food transport.
MCQs:
11. Succulent organs are present in:
Options:
a) Xerophytes
b) Hydrophytes
c) Mesophytes
d) Halophytes
Answer: a) Xerophytes
Explanation: Xerophytes are plants adapted to dry environments, and their succulent organs store water to survive droughts.
Tip: “Xero” means dry, so remember xerophytes store water.
Short Answers (3 lines each):
- Define mineral nutrition in plants.
Mineral nutrition involves the uptake of essential nutrients like nitrogen, phosphorus, and potassium from the soil, which plants use for growth and development. - Define macronutrients and micronutrients and give examples.
Macronutrients are needed in large amounts (e.g., nitrogen, phosphorus), while micronutrients are needed in small amounts (e.g., iron, zinc). - State the roles of nitrogen and magnesium in plants.
Nitrogen helps in protein synthesis and plant growth. Magnesium is essential for chlorophyll production and photosynthesis. - Define transpiration and its types.
Transpiration is the loss of water vapor from plant surfaces, mainly through stomata. Types include stomatal, cuticular, and lenticular transpiration. - How is the transpiration pull important in plants?
Transpiration pull helps transport water and minerals from roots to leaves, supporting photosynthesis and maintaining plant structure. - Transpiration is the loss of water from plants. Is it harmful?
Transpiration can be harmful during droughts, but it also cools the plant, supports nutrient transport, and maintains water flow. - Differentiate between Xylem and Phloem:
- Xylem: Transports water and minerals.
- Phloem: Transports food (sucrose).
- How do the plants of rubber and keekar excrete their wastes?
Rubber trees excrete waste as latex, while keekar trees excrete waste through leaf shedding and bark.
Detailed Answers:
1. Describe the events involved in the opening and closing of stomata.
Stomata are tiny openings on the surface of leaves, controlled by guard cells. Their opening and closing depend on water movement and ion concentration:
- Opening of stomata:
- During the day, guard cells actively absorb potassium ions (K⁺) from surrounding cells.
- This increases the solute concentration inside guard cells, causing water to enter by osmosis.
- The guard cells swell and become turgid, bending outward to open the stomatal pore.
- This allows gases like carbon dioxide to enter for photosynthesis and oxygen to exit.
- Closing of stomata:
- At night or in dry conditions, potassium ions leave the guard cells, reducing their solute concentration.
- Water moves out of the guard cells, making them flaccid and closing the stomatal pore.
- This prevents water loss through transpiration.
Importance:
The stomata help regulate water loss, maintain plant hydration, and allow essential gas exchange for photosynthesis and respiration.
2. Explain the internal structure of roots and describe the uptake of salt and water.
Roots are specially adapted for water and mineral uptake. The key parts are:
- Root hairs: Tiny hair-like structures increase surface area for water and nutrient absorption.
- Cortex: A layer of loosely packed cells that allows easy movement of water and nutrients.
- Endodermis: A barrier that ensures selective absorption of minerals.
- Xylem and phloem: Xylem transports water and minerals, while phloem transports food.
Water uptake:
- Water enters the root hairs from the soil by osmosis (movement from high to low water potential).
- It travels through the root cortex to the xylem, either through cell walls (apoplast pathway) or through the cytoplasm (symplast pathway).
Salt uptake:
- Minerals are absorbed by active transport, a process that requires energy in the form of ATP. This allows plants to take up nutrients even when their concentration in the soil is low.
Importance:
This mechanism ensures the plant receives water and nutrients for growth, photosynthesis, and development.
3. Describe temperature, wind, and humidity as factors affecting transpiration.
Transpiration is the loss of water vapor from plant leaves, mainly through stomata. It is influenced by environmental factors:
- Temperature:
- High temperatures increase evaporation of water from leaf surfaces, raising the rate of transpiration.
- At low temperatures, transpiration slows down because evaporation is reduced.
- Wind:
- Wind blows away water vapor around the leaves, creating a low-humidity environment.
- This increases the water concentration gradient between the leaf and the surrounding air, speeding up transpiration.
- Humidity:
- High humidity (moist air) reduces the rate of transpiration because the air already has a high water content.
- Low humidity (dry air) increases transpiration as water vapor diffuses more quickly.
Importance:
These factors affect a plant’s water balance, cooling, and nutrient transport.
4. Describe the mechanism of transport of water and salt in plants.
Plants transport water and salts from the roots to other parts through the xylem:
- Root pressure:
- Minerals actively absorbed by roots create a pressure that pushes water upward in the xylem.
- Capillary action:
- Water rises in the narrow xylem vessels due to adhesion (water sticking to the vessel walls) and cohesion (water molecules sticking to each other).
- Transpiration pull:
- As water evaporates from leaves during transpiration, it creates a negative pressure in the xylem that pulls water upward from the roots.
Salt transport:
Salts are absorbed by active transport and move with water through the xylem. This ensures the plant receives essential nutrients for growth.
5. Explain the mechanism of food translocation by Pressure Flow Mechanism.
Food (mainly sucrose) is transported through the phloem using the pressure flow mechanism:
- At the source (e.g., leaves):
- Sucrose is actively loaded into the phloem sieve tubes.
- This increases solute concentration, causing water from the xylem to enter by osmosis.
- The pressure builds up, pushing the sucrose solution (sap) toward the sink.
- At the sink (e.g., roots or fruits):
- Sucrose is actively unloaded and used for energy or storage.
- Water exits the phloem, reducing pressure and maintaining flow from source to sink.
Importance:
This mechanism efficiently transports food to growing parts, storage organs, and roots.
6. How do the plants excrete extra water and salts from their bodies?
Plants excrete waste through:
- Transpiration: Excess water is lost as vapor through stomata.
- Guttation: In some plants, water droplets are expelled from leaf edges (hydathodes) during the night or early morning.
- Salt excretion: Halophytes excrete salts through special salt glands. Other plants store excess salts in leaves, which are later shed.
Importance:
These processes help plants maintain a balance of water and salts, preventing toxicity and dehydration.
7. Describe the process of gaseous exchange in plants.
Gaseous exchange in plants occurs through stomata and lenticels:
- Daytime:
- Carbon dioxide enters through stomata for photosynthesis.
- Oxygen, a byproduct of photosynthesis, exits through stomata.
- Nighttime:
- Plants take in oxygen for respiration and release carbon dioxide as a waste product.
Importance:
This exchange is crucial for photosynthesis and cellular respiration, providing energy and maintaining life processes.
8. Describe the mechanisms/adaptations in plants for excretion of wastes.
Plants manage waste through:
- Storage in vacuoles: Toxic substances are stored in vacuoles or in old tissues like bark and leaves.
- Excretion through leaves: Some waste products are expelled when leaves shed.
- Salt excretion: Halophytes (e.g., mangroves) excrete salts through specialized salt glands.
Importance:
These mechanisms help plants survive in challenging environments and prevent waste accumulation.
9. Explain osmotic adjustments in hydrophytes, xerophytes, and halophytes.
- Hydrophytes:
- Adapted to water-rich environments.
- Excess water is stored or lost through transpiration.
- Xerophytes:
- Adapted to dry environments.
- Store water in succulent tissues, have thick waxy cuticles, and small leaves to reduce water loss.
- Halophytes:
- Adapted to saline conditions.
- Excrete excess salts through salt glands or store salts in vacuoles.
Importance:
These adjustments allow plants to survive and grow in their specific environments1. Describe the events involved in the opening and closing of stomata.
Stomata are tiny openings on the surface of leaves, controlled by guard cells. Their opening and closing depend on water movement and ion concentration:
- Opening of stomata:
- During the day, guard cells actively absorb potassium ions (K⁺) from surrounding cells.
- This increases the solute concentration inside guard cells, causing water to enter by osmosis.
- The guard cells swell and become turgid, bending outward to open the stomatal pore.
- This allows gases like carbon dioxide to enter for photosynthesis and oxygen to exit.
- Closing of stomata:
- At night or in dry conditions, potassium ions leave the guard cells, reducing their solute concentration.
- Water moves out of the guard cells, making them flaccid and closing the stomatal pore.
- This prevents water loss through transpiration.
Importance:
The stomata help regulate water loss, maintain plant hydration, and allow essential gas exchange for photosynthesis and respiration.
2. Explain the internal structure of roots and describe the uptake of salt and water.
Roots are specially adapted for water and mineral uptake. The key parts are:
- Root hairs: Tiny hair-like structures increase surface area for water and nutrient absorption.
- Cortex: A layer of loosely packed cells that allows easy movement of water and nutrients.
- Endodermis: A barrier that ensures selective absorption of minerals.
- Xylem and phloem: Xylem transports water and minerals, while phloem transports food.
Water uptake:
- Water enters the root hairs from the soil by osmosis (movement from high to low water potential).
- It travels through the root cortex to the xylem, either through cell walls (apoplast pathway) or through the cytoplasm (symplast pathway).
Salt uptake:
- Minerals are absorbed by active transport, a process that requires energy in the form of ATP. This allows plants to take up nutrients even when their concentration in the soil is low.
Importance:
This mechanism ensures the plant receives water and nutrients for growth, photosynthesis, and development.
3. Describe temperature, wind, and humidity as factors affecting transpiration.
Transpiration is the loss of water vapor from plant leaves, mainly through stomata. It is influenced by environmental factors:
- Temperature:
- High temperatures increase evaporation of water from leaf surfaces, raising the rate of transpiration.
- At low temperatures, transpiration slows down because evaporation is reduced.
- Wind:
- Wind blows away water vapor around the leaves, creating a low-humidity environment.
- This increases the water concentration gradient between the leaf and the surrounding air, speeding up transpiration.
- Humidity:
- High humidity (moist air) reduces the rate of transpiration because the air already has a high water content.
- Low humidity (dry air) increases transpiration as water vapor diffuses more quickly.
Importance:
These factors affect a plant’s water balance, cooling, and nutrient transport.
4. Describe the mechanism of transport of water and salt in plants.
Plants transport water and salts from the roots to other parts through the xylem:
- Root pressure:
- Minerals actively absorbed by roots create a pressure that pushes water upward in the xylem.
- Capillary action:
- Water rises in the narrow xylem vessels due to adhesion (water sticking to the vessel walls) and cohesion (water molecules sticking to each other).
- Transpiration pull:
- As water evaporates from leaves during transpiration, it creates a negative pressure in the xylem that pulls water upward from the roots.
Salt transport:
Salts are absorbed by active transport and move with water through the xylem. This ensures the plant receives essential nutrients for growth.
5. Explain the mechanism of food translocation by Pressure Flow Mechanism.
Food (mainly sucrose) is transported through the phloem using the pressure flow mechanism:
- At the source (e.g., leaves):
- Sucrose is actively loaded into the phloem sieve tubes.
- This increases solute concentration, causing water from the xylem to enter by osmosis.
- The pressure builds up, pushing the sucrose solution (sap) toward the sink.
- At the sink (e.g., roots or fruits):
- Sucrose is actively unloaded and used for energy or storage.
- Water exits the phloem, reducing pressure and maintaining flow from source to sink.
Importance:
This mechanism efficiently transports food to growing parts, storage organs, and roots.
6. How do the plants excrete extra water and salts from their bodies?
Plants excrete waste through:
- Transpiration: Excess water is lost as vapor through stomata.
- Guttation: In some plants, water droplets are expelled from leaf edges (hydathodes) during the night or early morning.
- Salt excretion: Halophytes excrete salts through special salt glands. Other plants store excess salts in leaves, which are later shed.
Importance:
These processes help plants maintain a balance of water and salts, preventing toxicity and dehydration.
7. Describe the process of gaseous exchange in plants.
Gaseous exchange in plants occurs through stomata and lenticels:
- Daytime:
- Carbon dioxide enters through stomata for photosynthesis.
- Oxygen, a byproduct of photosynthesis, exits through stomata.
- Nighttime:
- Plants take in oxygen for respiration and release carbon dioxide as a waste product.
Importance:
This exchange is crucial for photosynthesis and cellular respiration, providing energy and maintaining life processes.
8. Describe the mechanisms/adaptations in plants for excretion of wastes.
Plants manage waste through:
- Storage in vacuoles: Toxic substances are stored in vacuoles or in old tissues like bark and leaves.
- Excretion through leaves: Some waste products are expelled when leaves shed.
- Salt excretion: Halophytes (e.g., mangroves) excrete salts through specialized salt glands.
Importance:
These mechanisms help plants survive in challenging environments and prevent waste accumulation.
9. Explain osmotic adjustments in hydrophytes, xerophytes, and halophytes.
- Hydrophytes:
- Adapted to water-rich environments.
- Excess water is stored or lost through transpiration.
- Xerophytes:
- Adapted to dry environments.
- Store water in succulent tissues, have thick waxy cuticles, and small leaves to reduce water loss.
- Halophytes:
- Adapted to saline conditions.
- Excrete excess salts through salt glands or store salts in vacuoles.
Importance:
These adjustments allow plants to survive and grow in their specific environments
