CBSE Class 10 Biology Life Processes MCQs Set 21

Answer: (b) excretion

Explanation:
1. Excretion removes metabolic nitrogenous wastes such as urea.
2. Egestion is removal of undigested food through the anus and secretion is release of useful substances by cells.

Teacher's Note:
1. Nitrogenous wastes come from breakdown of proteins and nucleic acids.
2. Egestion is not a part of excretion.

Answer: (a) proteins and nucleic acids

Explanation:
1. Only proteins and nucleic acids contain nitrogen.
2. Carbohydrates and fats contain carbon, hydrogen and oxygen only.

Teacher's Note:
1. Ammonia, urea and uric acid are the nitrogenous wastes.
2. They become toxic if allowed to accumulate.

Answer: (d) ammonotelic

Explanation:
1. Ammonotelic animals such as bony fishes and tadpoles excrete ammonia.
2. Ammonia is very toxic but dissolves in plenty of water and can be removed quickly.

Teacher's Note:
1. Ureotelic animals include mammals, frogs and sharks.
2. Uricotelic animals include birds, reptiles and insects.

Answer: (c) uric acid

Explanation:
1. Uric acid is almost insoluble and is passed with little water, which saves water.
2. This is suitable for animals living on land with limited water.

Teacher's Note:
1. They are called uricotelic.
2. Insects also excrete uric acid.

Answer: (b) urea

Explanation:
1. Urea is made in the liver from ammonia by the ornithine cycle.
2. Humans are ureotelic.

Teacher's Note:
1. It is carried by blood to the kidneys.
2. Normal urine is mainly water and urea.

Answer: (a) nephridia

Explanation:
1. Earthworms have nephridia in the body segments.
2. Malpighian tubules are in insects and flame cells in flatworms.

Teacher's Note:
1. Match the animals with their excretory structures.
2. Amoeba excretes through the cell surface.

Answer: (c) kidney

Explanation:
1. Kidneys filter blood and remove urea and excess water as urine.
2. Lungs, skin and liver are accessory excretory organs.

Teacher's Note:
1. Kidneys also maintain water and salt balance.
2. This is homeostasis.

Answer: (b) Pancreas

Explanation:
1. The pancreas is a digestive gland and an endocrine gland.
2. The excretory system has kidneys, ureters, bladder and urethra.

Teacher's Note:
1. A pair of kidneys and a pair of ureters are present.
2. Urine passes from the bladder out through the urethra.

Answer: (a) ureter

Explanation:
1. Each ureter starts at the hilum of a kidney and opens into the bladder.
2. The urethra carries urine from the bladder to the outside.

Teacher's Note:
1. Remember the order: kidney, ureter, bladder, urethra.
2. The renal vein carries blood away from the kidney.

Answer: (b) PCT, loop of Henle, DCT, collecting duct

Explanation:
1. Filtrate passes from the capsule to the proximal convoluted tubule, then the U shaped loop of Henle, then the distal convoluted tubule, and finally the collecting duct.
2. The collecting duct collects from several nephrons.

Teacher's Note:
1. PCT is proximal and DCT is distal, which tells the order.
2. The loop of Henle lies in the medulla.

Answer: (a) ultrafiltration

Explanation:
1. Blood plasma is filtered under pressure in the glomerulus.
2. The filtrate has water, glucose, amino acids, ions and urea.

Teacher's Note:
1. The three steps are filtration, reabsorption and secretion.
2. Glomerular capillaries are more permeable than ordinary capillaries.

Answer: (c) Glucose

Explanation:
1. Glucose is useful and is returned to blood in the tubule.
2. Urea and other wastes remain in the filtrate and are excreted.

Teacher's Note:
1. Glucose in urine suggests diabetes mellitus.
2. This is why a healthy person's urine has no glucose.

Answer: (a) ADH (vasopressin)

Explanation:
1. ADH makes the distal tubule and collecting duct more permeable to water.
2. More water is returned to the blood and a small volume of concentrated urine is made.

Teacher's Note:
1. ADH is released from the pituitary gland.
2. Aldosterone from the adrenal gland regulates salts.

Answer: (a) urochrome

Explanation:
1. Urochrome is formed in the breakdown of haemoglobin.
2. It is the pigment that gives urine its pale yellow colour.

Teacher's Note:
1. The main components of urine are water and urea.
2. Colour depends on the concentration of urine.

Answer: (d) dialysis

Explanation:
1. In haemodialysis the blood passes through tubes of semipermeable membrane in a dialysing solution.
2. Urea and other wastes diffuse out of blood into the solution.

Teacher's Note:
1. The dialysing solution has no urea.
2. The cleaned blood is returned to a vein of the patient.

Answer: (c) urea

Explanation:
1. The absence of urea ensures that urea diffuses out from blood into the solution.
2. Glucose and salts are at the same levels as in normal blood so these are not lost.

Teacher's Note:
1. Diffusion needs a concentration difference.
2. The membrane is semipermeable (like cellophane).

Answer: (b) Shedding of leaves and peeling of bark

Explanation:
1. Plants store wastes in leaves and bark, which are then shed.
2. Plants have no definite excretory organs.

Teacher's Note:
1. Wastes like resins and gums are stored in old xylem.
2. Aquatic plants remove wastes by diffusion into water.

Answer: (d) photosynthesis

Explanation:
1. Oxygen is released by photosynthesis in the day and removed through stomata.
2. Respiration produces CO2 and water.

Teacher's Note:
1. Excess water is removed by transpiration.
2. CO2 from respiration is used up in photosynthesis in the day.

Answer: (c) removes undigested food and not metabolic wastes

Explanation:
1. Undigested material was never part of body cells, so it is not a metabolic waste.
2. Excretion removes wastes of metabolism such as urine and sweat.

Teacher's Note:
1. Egestion occurs through the anus.
2. Defecation is another name for egestion.