Class 09 Biology - Tissues in Action

Activities

Activity 3.1: Growth of Roots in Onion Bulbs

Aim/Objective: To observe the growth of roots in onion bulbs and demonstrate that growth occurs primarily at the tips (apical meristems).

Materials Required:

• Two glass jars
• Two onion bulbs
• Water
• Scissors/Knife
• Ruler

Procedure:

1. Fill two glass jars with water.
2. Place one onion bulb on each jar so that the base of the bulb touches the water.
3. Observe the growth of roots for three days and measure their lengths.
4. On day 3, cut the root tips of the onion bulb in Jar B by about 1 cm.
5. Continue observing and measuring the roots in both jars for four more days.

Observation:

• Roots in Jar A continue to grow in length daily.
• Roots in Jar B stop growing after their tips are removed.

Explanation:

• Growth in plants is restricted to specific regions containing actively dividing cells called meristematic tissues.
• The apical meristem is located at the tips of roots and shoots. It is responsible for the increase in length (primary growth).
• When the root tips in Jar B were cut, the apical meristematic tissue was removed. Since the source of new cell production was gone, the roots could no longer increase in length.

Conclusion:

• Plant growth in length occurs at the root and shoot tips due to the presence of apical meristems.

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Activity 3.2: Daily Life Observations of Blood and Infection

Aim/Objective: To correlate everyday physiological experiences with the functions of blood components.

Materials Required:

• Personal observations/Daily life experiences

Procedure:

1. Recall the experience of getting a small cut on the skin.
2. Recall what happens when a skin area gets infected (redness, swelling, pus).
3. Observe physical changes after vigorous exercise (faster breathing, red face).
4. Analyze the biological reasons for these events.

Observation:

• Cuts stop bleeding after some time (clotting).
• Infected areas become red, swollen, and may form pus.
• Exercise leads to increased heart rate and facial flushing.

Explanation:

• Clotting: Triggered by platelets which release factors to form a fibrin mesh, preventing excessive blood loss.
• Infection: Redness and swelling (inflammation) are caused by increased blood flow and the accumulation of White Blood Cells (WBCs) at the site to fight pathogens. Pus consists of dead WBCs and bacteria.
• Exercise: Increased oxygen demand by muscles causes the heart to pump blood faster. The red flush is due to the dilation of blood capillaries near the skin surface to dissipate heat and transport oxygen.

Conclusion:

• Blood is a vital connective tissue that handles transport, protection, and temperature regulation in the body.

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Activity 3.3: Identification of Connective Tissues through Action

Aim/Objective: To identify various connective tissues based on their physical properties and locations in the human body.

Materials Required:

• Own body joints and muscles

Procedure:

1. Touch your elbow and feel the hard structure.
2. Press and fold your ear or the tip of your nose.
3. Wiggle your fingers while touching your forearm muscles.
4. Sit and move your leg upwards at the knee until it stops.

Observation:

• The elbow feels hard and rigid (Bone).
• The ear/nose feels soft, flexible, and regains shape (Cartilage).
• Movement is felt in the forearm when fingers move (Tendon).
• The knee joint has a limited range of motion (Ligament).

Explanation:

• Bone: Has a rigid matrix of calcium and phosphorus; provide the structural framework.
• Cartilage: Has a flexible, jelly-like matrix; cushions joints and maintains shape of flexible organs.
• Tendons: Tough, non-flexible cords that connect muscle to bone, allowing the muscle's contraction to move the skeleton.
• Ligaments: Strong, elastic tissues that connect bone to bone, providing stability and preventing dislocation.

Conclusion:

• Different types of connective tissues are specialized for structural support, flexibility, and movement.

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Activity 3.4: Estimating Bone and Muscle Mass

Aim/Objective: To estimate the percentage of total body weight contributed by bones and muscles.

Materials Required:

• Weighing scale
• Reference data for body composition

Procedure:

1. Measure and record your total body weight.
2. Use standard physiological averages: Muscles (approx. 40-50% for males, 30-40% for females) and Bones (approx. 12-15% for adults).
3. Calculate the estimated weight of your bones and muscles.

Observation:

• Muscles account for nearly half of the body weight, while the skeleton, despite its strength, is relatively light.

Explanation:

• Muscles are dense and constitute a large portion of the body to facilitate movement and maintain posture.
• Bones are engineered to be extremely strong yet lightweight (often hollow or porous inside) to allow for efficient locomotion without requiring excessive energy to move the frame.

Conclusion:

• The distribution of body mass reflects the functional needs for both structural support and active movement.

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Activity 3.5: Observing Range of Motion in Joints

Aim/Objective: To categorize different types of skeletal joints based on the movement they allow.

Materials Required:

• Own body joints

Procedure:

1. Rotate your shoulder in a full circle.
2. Try to bend and straighten your elbow.
3. Turn your neck from side to side.
4. Attempt to move the bones of your skull (cranium).

Observation:

• Shoulder: Moves in all directions (Ball and Socket Joint).
• Elbow: Moves in one plane only (Hinge Joint).
• Neck: Side-to-side rotation (Pivot Joint).
• Skull: No movement possible (Fixed Joint).

Explanation:

• Joints are junctions where bones meet. Their structure determines the degree of freedom.
• Ball and socket joints (shoulder/hip) allow maximum mobility. Hinge joints (elbow/knee) provide stability and strength in one direction. Pivot joints (neck) allow rotation. Fixed joints (skull) provide maximum protection to delicate organs like the brain.

Conclusion:

• The variety of joints in the skeletal system balances the need for mobility with the requirements for stability and protection.