Unit Test (Solutions): Transport in Animals and Plants | Science Class 7 PDF Download

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Time: 1 hour
Maximum Marks: 30
Attempt all questions.

• Question numbers 1 to 5 carry 1 mark each.
• Question numbers 6 to 8 carry 2 marks each.
• Question numbers 9 to 11 carry 3 marks each.
• Question numbers 12 & 13 carry 5 marks each.

Q1: Which component of blood is responsible for transporting oxygen?  (1 Mark)
(a) White blood cells
(b) Red blood cells
(c) Platelets
(d) Plasma
Ans: (b) Red blood cells
RBCs contain hemoglobin, which binds with oxygen and carries it throughout the body.

Q2: What is the function of platelets in blood?  (1 Mark)
Ans: Platelets help in blood clotting and prevent excessive bleeding when there is an injury.

Q3: Name the blood vessel that carries oxygenated blood from the lungs to the heart.  (1 Mark)
Ans: Pulmonary vein

Q4: Which plant vascular tissue is responsible for transporting food?  (1 Mark)
(a) Xylem
(b) Phloem
(c) Stomata
(d) Root hairs
Ans: (b) Phloem
Phloem transports food produced in the leaves to all parts of the plant.

Q5: What is the function of the kidneys in the excretory system?  (1 Mark)
Ans: The kidneys filter waste products like urea from the blood and remove them in the form of urine.

Q6: Differentiate between arteries and veins.  (2 Marks)
Ans:

• Arteries carry oxygen-rich blood away from the heart and have thick, elastic walls to handle high pressure.
• Veins carry oxygen-poor blood toward the heart and have thin walls with valves to prevent backflow.

Q7: What is transpiration, and how does it help plants?  (2 Marks)
Ans: Transpiration is the process where plants lose water vapor through stomata. It helps in:

1. Cooling the plant.
2. Creating a suction force (transpiration pull) that helps transport water and minerals from roots to leaves.

Q8: How does sweating help in cooling the human body?  (2 Marks)
Ans: Sweating releases water and salts from the body. As sweat evaporates from the skin, it absorbs heat, cooling the body.

Q9: Explain the role of hemoglobin in the transport of gases in the body.  (3 Marks)
Ans:

• Hemoglobin, a protein in red blood cells, binds with oxygen in the lungs.
• It transports oxygen through blood and releases it into body cells.
• Hemoglobin also carries carbon dioxide from cells back to the lungs for exhalation.

Q10: Describe how the structure of the heart prevents the mixing of oxygen-rich and oxygen-poor blood.  (3 Marks)
Ans:

• The heart has four chambers: two atria and two ventricles.
• A septum (wall) separates the left and right sides of the heart.
• The left side receives oxygen-rich blood and pumps it to the body, while the right side receives oxygen-poor blood and sends it to the lungs.
• This structure ensures no mixing of oxygenated and deoxygenated blood.

Q11: How do aquatic and terrestrial animals excrete waste differently?  (3 Marks)
Ans:

• Aquatic animals (e.g., fish) excrete ammonia directly into water as it dissolves easily.
• Terrestrial animals (e.g., humans, birds, lizards) conserve water by excreting urea (humans) or uric acid (birds and reptiles), which requires less water for elimination.

Q12: Explain the process of urine formation in humans.  (5 Marks)
Ans:

1. Filtration: Blood is filtered in the kidneys through tiny capillaries. Harmful substances like urea and extra salts are removed.
2. Reabsorption: Useful substances like water and nutrients are reabsorbed into the blood.
3. Urine Formation: The remaining waste combines with water to form urine.
4. Transport Through Ureters: Urine travels from kidneys to the urinary bladder via ureters.
5. Storage and Elimination: Urine is temporarily stored in the bladder and excreted through the urethra.

Urine consists of 95% water, 2.5% urea, and 2.5% other waste products.

Q13: How does the circulatory system work in coordination with the respiratory system to transport oxygen in the body? (5 Marks)
Ans:

1. Oxygen intake (Respiratory System): Lungs absorb oxygen from inhaled air.
2. Transport via Blood (Circulatory System): Oxygen binds with hemoglobin in RBCs and is transported by arteries.
3. Delivery to Cells: Oxygen is released into body cells for energy production.
4. Carbon Dioxide Removal: Blood collects carbon dioxide waste from cells and carries it back to the lungs through veins.
5. Exhalation (Respiratory System): Lungs expel carbon dioxide when we breathe out.

This coordination ensures continuous oxygen supply and waste removal for survival.