Respiration, Circulation and Excretion Practice Questions
20 free Respiration, Circulation and Excretion practice questions for the Zoology. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.
The primary function of the respiratory system is to:
- A Transport nutrients
- B Exchange gases with the environment
- C Remove nitrogenous wastes from the body
- D Regulate body temperature
Correct answer: Exchange gases with the environment
The respiratory system enables exchange of oxygen and carbon dioxide. Oxygen is taken in for cellular respiration, while carbon dioxide is expelled as a waste gas.
In humans, gas exchange occurs mainly in the:
- A Bronchi
- B The trachea (windpipe)
- C Alveoli
- D Larynx
Correct answer: Alveoli
Alveoli are thin-walled air sacs surrounded by capillaries. Their large surface area facilitates efficient gas exchange.
Hemoglobin is primarily responsible for transporting:
- A Carbon dioxide
- B Oxygen
- C Nitrogen
- D Urea
Correct answer: Oxygen
Hemoglobin in red blood cells binds oxygen reversibly. This allows efficient transport of oxygen from lungs to tissues.
Which blood vessel carries oxygenated blood from the lungs to the heart?
- A Pulmonary artery
- B Pulmonary vein
- C Aorta
- D Vena cava
Correct answer: Pulmonary vein
The pulmonary vein carries oxygen-rich blood from the lungs to the left atrium of the heart. It is unique among veins in carrying oxygenated blood.
The main pumping chamber of the human heart is the:
- A Right atrium
- B Left atrium
- C Right ventricle
- D Left ventricle
Correct answer: Left ventricle
The left ventricle pumps oxygenated blood to the entire body. It has the thickest muscular wall to generate high pressure.
Which component of blood is involved in clotting?
- A Red blood cells
- B White blood cells
- C Platelets
- D Plasma proteins only
Correct answer: Platelets
Platelets play a crucial role in blood clotting. They aggregate at injury sites and release clotting factors.
The circulatory system primarily helps in:
- A Digestion of food
- B Transport of substances
- C Excretion of urine
- D Exchange of gases directly
Correct answer: Transport of substances
The circulatory system transports gases, nutrients, hormones, and wastes. It connects all body systems through blood flow.
Which structure prevents backflow of blood in the heart?
- A Septum
- B Valves
- C Chordae tendineae
- D Papillary muscles
Correct answer: Valves
Heart valves ensure one-way flow of blood. They prevent backflow during contraction and relaxation of chambers.
Carbon dioxide is mainly transported in blood as:
- A Dissolved gas
- B Carbaminohemoglobin
- C Bicarbonate ions
- D Carbonic acid
Correct answer: Bicarbonate ions
Most carbon dioxide is transported as bicarbonate ions in plasma. This form allows efficient carriage of large amounts of CO₂.
The basic functional unit of the kidney is the:
- A Neuron
- B Nephron
- C Alveolus
- D Glomerulus
Correct answer: Nephron
Nephrons are the structural and functional units of kidneys. Each nephron filters blood and forms urine.
Which process occurs in the glomerulus of the nephron?
- A Selective reabsorption
- B Tubular secretion
- C Ultrafiltration
- D Urine storage
Correct answer: Ultrafiltration
Ultrafiltration occurs in the glomerulus due to high blood pressure. It filters plasma into the Bowman’s capsule.
The main nitrogenous waste excreted in humans is:
- A Ammonia
- B Uric acid
- C Urea
- D Creatinine
Correct answer: Urea
Humans are ureotelic and excrete urea as the main nitrogenous waste. Urea is less toxic than ammonia.
Which hormone regulates water reabsorption in kidneys?
- A Insulin
- B Aldosterone steroid hormone
- C Antidiuretic hormone
- D Thyroxine
Correct answer: Antidiuretic hormone
Antidiuretic hormone increases water reabsorption in collecting ducts. It helps maintain fluid balance.
Which blood vessel carries deoxygenated blood from body tissues to the heart?
- A Aorta
- B Pulmonary vein
- C Vena cava
- D Pulmonary artery
Correct answer: Vena cava
The vena cava returns deoxygenated blood from the body to the right atrium. It includes superior and inferior vena cava.
Breathing is controlled by the respiratory center located in the:
- A Cerebrum
- B Cerebellum
- C Medulla oblongata
- D Hypothalamus region
Correct answer: Medulla oblongata
The medulla oblongata contains respiratory centers that regulate breathing rhythm. It responds to CO₂ levels in blood.
Which component of blood provides immunity?
- A Red blood cells
- B White blood cells
- C Platelets
- D Plasma proteins only
Correct answer: White blood cells
White blood cells protect the body against pathogens. They are key components of the immune system.
Selective reabsorption of glucose mainly occurs in the:
- A The Bowman’s capsule region
- B Loop of Henle
- C Proximal convoluted tubule
- D Collecting duct
Correct answer: Proximal convoluted tubule
The proximal convoluted tubule reabsorbs most glucose, amino acids, and ions. This conserves essential nutrients.
Which structure separates the right and left sides of the heart?
- A Valve
- B Chordae tendineae
- C Septum
- D Pericardium
Correct answer: Septum
The septum divides the heart into right and left halves. It prevents mixing of oxygenated and deoxygenated blood.
The primary role of the loop of Henle is to:
- A Filter the blood
- B Reabsorb plasma proteins
- C Concentrate urine
- D Store urine
Correct answer: Concentrate urine
The loop of Henle creates a concentration gradient in the medulla. This enables formation of concentrated urine.
Which gas is the main stimulus for breathing in humans?
- A Oxygen
- B Nitrogen
- C Carbon dioxide
- D Carbon monoxide
Correct answer: Carbon dioxide
Elevated carbon dioxide levels stimulate the respiratory center. This increases breathing rate to expel excess CO₂.