Class 10 Biology - Control and Coordination

Activities

Activity 6.1: Interdependence of Taste and Smell

Aim/Objective: To quantify the contribution of retro-nasal olfaction to the perception of food flavor.

Materials Required:

5.0g Crystalline Sucrose (table sugar)
A 2cm x 2cm slice of raw onion or a peeled apple
1 Nose clip or fingers
100 mL Distilled water (for palate cleansing)
Stopwatch

Procedure:

Rinse your mouth with distilled water. Place 2.0g of sugar on the tongue and record the perceived taste (sweetness) on a scale of 1–10.
Repeat the process while wearing a nose clip. Note any change in intensity.
Flavour Test: While wearing the nose clip, chew a piece of raw onion for 15 seconds. Note the perceived "flavor."
Remove the nose clip mid-chew (at the 15-second mark) and immediately observe the change in sensory input.
Record the time taken (in seconds) for the full "aroma" to be perceived after the nasal passage is opened.

Scientific Note While gustatory receptors (taste buds) on the tongue detect five basic non-volatile molecules (sweet, sour, salty, bitter, umami), olfactory receptors in the nasal epithelium detect thousands of volatile aromatic compounds. During chewing, these volatiles travel from the oropharynx to the nasal cavity—a process called retro-nasal olfaction.

Observation:

Pure sugar (Sucrose) intensity remains constant at ~8/10 regardless of nasal obstruction.
The onion piece feels like a generic "crunchy texture" with mild sweetness while the nose is clipped, but explodes into a pungent "onion flavor" the moment the clip is removed.

Explanation:

Flavor is a multi-modal construct. When the nasal passage is blocked, the brain receives only the "taste" component. Removing the clip allows volatile sulfur compounds from the onion to reach the olfactory bulb, completing the "flavor" profile.

Conclusion:

Olfactory input is the primary driver of flavor complexity, whereas gustatory input is limited to basic chemical detection.

Activity 6.2: Phototropism in Growing Plants

Aim/Objective: To observe and measure the differential growth rates in bean shoots in response to unidirectional light stimuli.

Materials Required:

250 mL Conical flask filled with 200 mL water
Galvanized wire mesh (2mm grid)
5 Freshly germinated Bean (Phaseolus vulgaris) seeds (hypocotyl length ~2cm)
30cm x 30cm x 30cm Cardboard box, painted matte black inside, with a 5cm x 5cm aperture on one side.
Protractor (to measure bending angle)
60W LED lamp (as a controlled light source)

Procedure:

Suspend the germinated seeds on the wire mesh so that the roots are in constant contact with the water in the flask.
Place the flask inside the cardboard box. Align the aperture so it faces the light source.
Maintain the setup at 25°C for 72 hours. Measure the angle of the shoot relative to the vertical axis every 24 hours.
On Day 3, rotate the flask 180° so the shoots face the dark side of the box.
Observe for another 48 hours and measure the "correction angle."

Lab Best Practice Ensure the interior of the box is matte black to prevent internal reflections (stray light), which can lead to "noisy" data and inconsistent bending angles.

Scientific Note Phototropism is mediated by Auxin (Indole-3-acetic acid). Under unidirectional light, auxin is actively transported to the shaded side of the shoot. Higher auxin concentration in the shaded cells stimulates proton pumps, lowering the pH and activating expansins that loosen the cell wall, leading to asymmetric elongation.

Observation:

Shoots exhibit a positive phototropic curvature of approx. 30°–45° towards the aperture within 48 hours. Roots show a distinct, though less pronounced, negative curvature (negative phototropism).

Explanation:

The shoot bends because the side further from the light grows faster than the side closer to the light. This ensures the primary photosynthetic organs (leaves) are positioned for maximum light interception (irradiance).

Conclusion:

Plants utilize hormonal gradients to execute precise directional movements (tropisms) for environmental optimization.

Activity 6.3: Identifying Human Endocrine Glands

Aim/Objective: To map the spatial distribution and anatomical coordinates of the human endocrine system.

Materials Required:

3D Human Anatomical Model or high-resolution endocrine chart
Magnifying lens
Colored markers (Red for master glands, Blue for metabolic glands)

Procedure:

Locate the Pituitary Gland at the base of the brain, housed within the Sella turcica of the sphenoid bone.
Identify the Thyroid Gland—a butterfly-shaped structure anterior to the trachea in the neck region.
Locate the Adrenal Glands (Suprarenal glands) positioned superior to each kidney at the T12-L1 vertebral level.
Find the Pancreas in the retroperitoneal space, posterior to the stomach.
Identify the Gonads (Testes in the scrotal sac; Ovaries in the pelvic cavity).

Scientific Note The Hypothalamus acts as the neuro-endocrine bridge. It synthesizes releasing and inhibiting hormones that travel through the hypophyseal portal system to control the anterior pituitary, earning the pituitary its title as the "Master Gland."

Observation:

Endocrine glands are widely dispersed but interconnected via the vascular system. Most are highly vascularized to ensure rapid hormone delivery.

Explanation:

Unlike exocrine glands (like sweat glands), endocrine glands are ductless. They secrete hormones into the interstitial fluid, which then diffuses into the capillaries for systemic transport.

Conclusion:

The endocrine system is a decentralized but highly integrated network that regulates long-term physiological changes.

Activity 6.4: Hormones and their Functions

Aim/Objective: To analyze the physiological impact and feedback regulation of major human hormones.

Materials Required:

Endocrine disorder case studies (e.g., Diabetes, Gigantism)
Standard reference table of hormone concentrations (pmol/L or ng/dL)

Procedure:

Review the "Feedback Mechanism" using Insulin as a model.
Analyze the "Fight or Flight" response triggered by Adrenaline.
Study the metabolic regulation by Thyroxin and the requirement of Iodine for its synthesis.

Critical Data Summary:

Hormone	Source	Primary Mechanism / Function
Growth Hormone (GH)	Anterior Pituitary	Stimulates protein synthesis and cell division in chondrocytes and osteoblasts.
Thyroxin (T4)	Thyroid Gland	Increases Basal Metabolic Rate (BMR) and regulates thermogenesis. Requires Iodine.
Insulin	Pancreas (Beta cells)	Facilitates glucose uptake into cells via GLUT4 transporters; lowers blood glucose.
Adrenaline	Adrenal Medulla	Increases glycogenolysis, heart rate, and bronchodilation during acute stress.
Testosterone	Testes (Leydig cells)	Regulates spermatogenesis and anabolic growth of muscle/bone.

Safety First Thyroxin deficiency (Hypothyroidism) during pregnancy can lead to Cretinism (severe mental and physical growth retardation) in the offspring. Ensure adequate dietary intake of Iodized salt (approx. 150 µg/day for adults).

Explanation:

Hormone levels are maintained by Negative Feedback Loops. For example, high blood glucose triggers insulin release; as glucose levels drop, insulin secretion is inhibited. This maintains Homeostasis.

Conclusion:

Hormones are potent biochemical regulators; even picomolar deviations in their concentration can lead to significant systemic pathologies.

Class 10 Biology - Control and Coordination

Activities

Activity 6.1: Interdependence of Taste and Smell

Aim/Objective: To quantify the contribution of retro-nasal olfaction to the perception of food flavor.

Materials Required:

5.0g Crystalline Sucrose (table sugar)
A 2cm x 2cm slice of raw onion or a peeled apple
1 Nose clip or fingers
100 mL Distilled water (for palate cleansing)
Stopwatch

Procedure:

Rinse your mouth with distilled water. Place 2.0g of sugar on the tongue and record the perceived taste (sweetness) on a scale of 1–10.
Repeat the process while wearing a nose clip. Note any change in intensity.
Flavour Test: While wearing the nose clip, chew a piece of raw onion for 15 seconds. Note the perceived "flavor."
Remove the nose clip mid-chew (at the 15-second mark) and immediately observe the change in sensory input.
Record the time taken (in seconds) for the full "aroma" to be perceived after the nasal passage is opened.

Observation:

Pure sugar (Sucrose) intensity remains constant at ~8/10 regardless of nasal obstruction.
The onion piece feels like a generic "crunchy texture" with mild sweetness while the nose is clipped, but explodes into a pungent "onion flavor" the moment the clip is removed.

Explanation:

Flavor is a multi-modal construct. When the nasal passage is blocked, the brain receives only the "taste" component. Removing the clip allows volatile sulfur compounds from the onion to reach the olfactory bulb, completing the "flavor" profile.

Conclusion:

Olfactory input is the primary driver of flavor complexity, whereas gustatory input is limited to basic chemical detection.

Activity 6.2: Phototropism in Growing Plants

Aim/Objective: To observe and measure the differential growth rates in bean shoots in response to unidirectional light stimuli.

Materials Required:

250 mL Conical flask filled with 200 mL water
Galvanized wire mesh (2mm grid)
5 Freshly germinated Bean (Phaseolus vulgaris) seeds (hypocotyl length ~2cm)
30cm x 30cm x 30cm Cardboard box, painted matte black inside, with a 5cm x 5cm aperture on one side.
Protractor (to measure bending angle)
60W LED lamp (as a controlled light source)

Procedure:

Suspend the germinated seeds on the wire mesh so that the roots are in constant contact with the water in the flask.
Place the flask inside the cardboard box. Align the aperture so it faces the light source.
Maintain the setup at 25°C for 72 hours. Measure the angle of the shoot relative to the vertical axis every 24 hours.
On Day 3, rotate the flask 180° so the shoots face the dark side of the box.
Observe for another 48 hours and measure the "correction angle."

Lab Best Practice Ensure the interior of the box is matte black to prevent internal reflections (stray light), which can lead to "noisy" data and inconsistent bending angles.

Observation:

Shoots exhibit a positive phototropic curvature of approx. 30°–45° towards the aperture within 48 hours. Roots show a distinct, though less pronounced, negative curvature (negative phototropism).

Explanation:

The shoot bends because the side further from the light grows faster than the side closer to the light. This ensures the primary photosynthetic organs (leaves) are positioned for maximum light interception (irradiance).

Conclusion:

Plants utilize hormonal gradients to execute precise directional movements (tropisms) for environmental optimization.

Activity 6.3: Identifying Human Endocrine Glands

Aim/Objective: To map the spatial distribution and anatomical coordinates of the human endocrine system.

Materials Required:

3D Human Anatomical Model or high-resolution endocrine chart
Magnifying lens
Colored markers (Red for master glands, Blue for metabolic glands)

Procedure:

Locate the Pituitary Gland at the base of the brain, housed within the Sella turcica of the sphenoid bone.
Identify the Thyroid Gland—a butterfly-shaped structure anterior to the trachea in the neck region.
Locate the Adrenal Glands (Suprarenal glands) positioned superior to each kidney at the T12-L1 vertebral level.
Find the Pancreas in the retroperitoneal space, posterior to the stomach.
Identify the Gonads (Testes in the scrotal sac; Ovaries in the pelvic cavity).

Observation:

Endocrine glands are widely dispersed but interconnected via the vascular system. Most are highly vascularized to ensure rapid hormone delivery.

Explanation:

Unlike exocrine glands (like sweat glands), endocrine glands are ductless. They secrete hormones into the interstitial fluid, which then diffuses into the capillaries for systemic transport.

Conclusion:

The endocrine system is a decentralized but highly integrated network that regulates long-term physiological changes.

Activity 6.4: Hormones and their Functions

Aim/Objective: To analyze the physiological impact and feedback regulation of major human hormones.

Materials Required:

Endocrine disorder case studies (e.g., Diabetes, Gigantism)
Standard reference table of hormone concentrations (pmol/L or ng/dL)

Procedure:

Review the "Feedback Mechanism" using Insulin as a model.
Analyze the "Fight or Flight" response triggered by Adrenaline.
Study the metabolic regulation by Thyroxin and the requirement of Iodine for its synthesis.

Critical Data Summary:

Hormone	Source	Primary Mechanism / Function
Growth Hormone (GH)	Anterior Pituitary	Stimulates protein synthesis and cell division in chondrocytes and osteoblasts.
Thyroxin (T4)	Thyroid Gland	Increases Basal Metabolic Rate (BMR) and regulates thermogenesis. Requires Iodine.
Insulin	Pancreas (Beta cells)	Facilitates glucose uptake into cells via GLUT4 transporters; lowers blood glucose.
Adrenaline	Adrenal Medulla	Increases glycogenolysis, heart rate, and bronchodilation during acute stress.
Testosterone	Testes (Leydig cells)	Regulates spermatogenesis and anabolic growth of muscle/bone.

Explanation:

Hormone levels are maintained by Negative Feedback Loops. For example, high blood glucose triggers insulin release; as glucose levels drop, insulin secretion is inhibited. This maintains Homeostasis.

Conclusion:

Hormones are potent biochemical regulators; even picomolar deviations in their concentration can lead to significant systemic pathologies.

Class 10 Biology - Control and Coordination

Class 10 Biology - Control and Coordination

Activities

Activity 6.1: Interdependence of Taste and Smell

Activity 6.2: Phototropism in Growing Plants

Activity 6.3: Identifying Human Endocrine Glands

Activity 6.4: Hormones and their Functions

On this page

Class 10 Biology - Control and Coordination

Class 10 Biology - Control and Coordination

Activities

Activity 6.1: Interdependence of Taste and Smell

Activity 6.2: Phototropism in Growing Plants

Activity 6.3: Identifying Human Endocrine Glands

Activity 6.4: Hormones and their Functions

On this page