Multiple Choice Questions & Fill in the Blanks
Official textbook exercise solutions and complete evaluation keys.
A. Multiple Choice Questions
i) The internal condition of an organism is referred as:
ii) A set of metabolic reactions which maintain the internal environment is:
iii) Removal of extra liquid water is:
iv) Plants growing near coastal areas are called:
v) The organ of the human body considered the largest organ is:
vi) The maintenance of body temperature within suitable limits is called:
vii) The kidney is enclosed in a membrane called:
viii) The network of blood capillaries present in the layer of skin:
ix) Selective reabsorption in the nephron takes place at:
x) The hormone ADH is released from the:
xi) Set point of human body temperature is:
B. Fill In The Blanks
- Homeostasis is a set of metabolic processes which maintain the internal environment of an organism within suitable limits.
- Organisms maintain internal conditions by feedback mechanisms.
- There are three main aspects of homeostasis i.e. osmoregulation, thermoregulation and excretion.
- Osmoregulation is the maintenance of internal water and salt conditions by osmosis.
- Thermoregulation is the maintenance of temperature within suitable limits where enzymes can work optimally.
- Excretion is the process where metabolic toxic wastes and excess substances are removed from the body.
- Hydrophytes are the plants which grow in fresh water.
- Halophytes grow in sea marshes or in saltish water.
- Mesophytes are the plants that grow in moderate water-containing soil.
- Xerophytes are the plants that grow in soil of low water quantity.
- The main organs involved in human homeostasis are skin, lungs and kidneys.
- Human skin consists of three layers called epidermis, dermis and hypodermis.
- When body temperature rises, the body produces sweat, hairs lie flat, and vasodilation occurs.
- When body temperature decreases, the erection of hairs, vasoconstriction, decrease in sweat production, and increase in metabolic rate occur.
- Lungs keep the CO₂ concentration at a low level.
- Kidneys maintain blood composition by maintaining the level of H₂O, solutes, and nitrogenous waste through the processes of filtration and reabsorption.
- Kidneys are situated at the dorsal side of the abdominal cavity on either side of the vertebral column.
- Nephrons are the functional unit of the kidney.
- Urea is formed in the liver and excreted from the kidneys.
- A mixture of urea, creatinine, uric acid, and water is called urine.
- A kidney stone is a solid mass made of calcium oxalate or carbonate crystals.
- Kidney failure patients can be treated with a dialysis machine, which performs the function of a kidney.
Short Conceptual Questions Answers
Precise, conceptual textbook definitions optimized for board examinations.
Why is homeostasis required?
Ans: Homeostasis is the regulatory framework that maintains the internal conditions of an organism within optimal, stable boundaries. It is required because vital cellular proteins called enzymes function effectively only within narrow ranges of temperature, pH, and fluid concentration. Homeostasis buffers internal systems against fluctuating environmental changes, guaranteeing uninterrupted cell metabolism.
Why do plants remove liquid water instead of water vapor during guttation?
Ans: At night or early in the morning, high soil moisture combined with low transpiration (due to closed stomata) generates immense root pressure. This forces excess liquid water containing dissolved minerals out through specialized pores called hydathodes at the leaf margins. This process, known as guttation, allows the plant to dump excess water pressure when evaporation is physically impossible due to cool ambient conditions.
How do plants survive in saltish water?
Ans: Halophytes grow in environments with high external salt concentrations. To stop water from rushing out of their cells by exosmosis, they adapt by: 1) Actively pumping and storing salts inside vacuoles using active transport; 2) Utilizing specialized salt glands on leaves to excrete excess mineral ions; and 3) Accumulating surface leaf salts to attract moisture directly from humid air.
Why is skin considered an excretory organ?
Ans: Even though skin primarily serves a protective purpose, it is classified as an excretory organ because its 3 to 4 million sweat glands actively filter out metabolic wastes like water, salts, and small amounts of urea from blood capillaries, expelling them as sweat onto the skin's surface.
What types of structures are present in the dermis to perform different functions?
Ans: The dermis is the highly functional middle layer of skin. It contains: 1) Specialized nerve endings (receptors) for pain, pressure, and temperature; 2) Sweat glands for thermal control and solute excretion; 3) Arterioles that constrict or dilate to regulate heat retention; and 4) Hair follicles along with sebaceous glands that produce oily sebum.
What is a kidney stone?
Ans: A kidney stone is a hardened crystal mass formed mainly from precipitated calcium oxalate, calcium carbonate, or uric acid inside the renal pelvis. Small stones can pass unnoticed through urine as fine crystals, but larger stones lodge inside ureters, tearing tissue layers, causing severe pain, and potentially blocking urine flow, which leads to kidney failure.
How does human skin maintain temperature in cold conditions?
Ans: When thermal skin receptors report a temperature drop to the brain, the skin preserves core warmth by: 1) Eerection of hairs (goosebumps) via contracting erector muscles to trap a layer of insulating air; 2) Vasoconstriction to reduce blood flow near the cold surface; 3) Stopping sweat production; and 4) Stimulating internal cellular metabolism to produce heat.
When is dialysis required?
Ans: Dialysis is required when a patient suffers from end-stage renal failure and a matching healthy kidney donor is not immediately available. The machine acts as an artificial kidney, filtering urea, creatinine, and toxic elements out of the patient's bloodstream 2 to 3 times a week to prevent fatal toxic chemical accumulation.
Why is filtration at Bowman's capsule called ultrafiltration?
Ans: It is called ultrafiltration because the high hydrostatic pressure inside the narrow glomerulus capillaries non-selectively forces almost all liquid components of blood plasma (water, glucose, salts, urea) across the basement membrane into Bowman's capsule, leaving behind only large blood cells and plasma proteins.
Long Comprehensive Extensive Questions
Detailed structural notes, metabolic pathways, and organ system breakdowns.
i) Important Aspects of Homeostasis
Homeostasis regulates three key processes to balance internal fluid environments:
- Osmoregulation: Balancing water and solute levels within cells and blood via osmotic pressure shifts.
- Thermoregulation: Maintaining structural core temperatures around an optimal $37^\circ\text{C}$ baseline so functional metabolic enzymes do not denature.
- Excretion: Removing toxic nitrogenous waste products ($\text{NH}_3$, urea, uric acid) generated during chemical interactions.
ii) Osmoregulation Categories in Plants
Plants are classified into four distinct ecophysiological categories based on their water availability habitats:
- Hydrophytes: Grow fully or partially submerged in fresh water. They lack waxy cuticles, have broad leaves with thousands of stomata on the upper epidermis, and have reduced root networks to maximize water loss. (e.g., Lotus, Hydrilla).
- Halophytes: Inhabit high-salt marine marshes. They use active transport to concentrate salts inside cellular vacuoles, developing a lower internal water potential that allows them to draw water inward from the salty sea. (e.g., Cordgrass).
- Mesophytes: Grow in temperate soils with moderate moisture. They feature well-developed roots, protective cuticles, and close their stomata during dry spells to prevent excessive evaporation. (e.g., Brassica, Rose).
- Xerophytes: Adapted to arid deserts. They feature deep vertical taproots, thick waxy cuticles, and leaves reduced to sharp spines to limit transpiration. They store water in fleshy stem cells called succulent tissue. (e.g., Cactus).
iii) Functional Anatomy of the Human Urinary System
The human urinary framework extracts dissolved urea wastes from blood plasma and includes four major components:
- A Pair of Kidneys: Reddish-brown, bean-shaped organs on the dorsal side of the abdominal cavity. The entry cleft is called the hilus, where the renal artery, renal vein, and ureter connect.
- A Pair of Ureters: Long, muscular tubes extending from the renal pelvis of each kidney down to the urinary bladder.
- Urinary Bladder: A distensible, muscular storage sac positioned at the bottom of the pelvic floor that temporarily holds urine.
- Urethra: The exit duct that carries stored urine out of the body during urination.
iv) Microscopic Structure of a Nephron
Nephrons are the structural and functional units of the kidney. Each kidney contains over one million of these microscopic filtering units, which are split into two major parts:
- Malpighian Body (Renal Corpuscle): Located in the cortex layer. It consists of the Glomerulus (a high-pressure capillary cluster branched from the afferent arteriole) nested inside the cup-like Bowman's Capsule.
- Renal Tubule: A long, continuous tube divided into the coiling Proximal Convoluted Tubule, the U-shaped Loop of Henle that dips deep into the renal medulla pyramids, and the final Distal Convoluted Tubule that empties into a central collecting duct.
v) The Physiology of Urine Formation
Kidneys produce urine via a highly regulated two-stage process inside the nephrons:
- Filtration: High fluid pressure forces water and solutes out of the glomerulus into Bowman's capsule during ultrafiltration. Then, during selective filtration in the convoluted segments, remaining wastes are actively pumped out from peritubular vessels using cellular energy.
- Reabsorption: To prevent fatal dehydration, approximately 99% of the initial filtrate volume (including essential water, glucose, and trace mineral ions) is pulled back into the surrounding capillaries. This occurs automatically in proximal sections and is fine-tuned by hormones like Antidiuretic Hormone (ADH) in the Loop of Henle and collecting ducts based on hydration levels.
Key Differences: Transpiration vs. Guttation
| Feature | Transpiration | Guttation |
|---|---|---|
| Time of Occurrence | Takes place during the day when temperatures are warm. | Occurs primarily at night or in the early morning. |
| Physical State | Water is lost entirely as invisible gas vapors. | Water is squeezed out as visible liquid droplets. |
| Exit Openings | Exits through stomata, lenticels, or plant cuticles. | Exits only through specialized terminal pores called hydathodes. |
| Purity of Water | Pure distilled $\text{H}_2\text{O}$ vapor without residues. | Impure liquid containing dissolved organic and inorganic salts. |
| Control State | Highly regulated by guard cell shape configurations. | Unregulated process driven entirely by high root pressure. |
Key Differences: Photosynthesis vs. Respiration
| Feature | Photosynthesis | Cellular Respiration |
|---|---|---|
| Metabolic Class | Anabolic process (constructs complex food molecules). | Catabolic process (breaks down food into compounds). |
| Gas Exchange | Consumes Carbon Dioxide ($\text{CO}_2$), releases Oxygen ($\text{O}_2$). | Consumes Oxygen ($\text{O}_2$), releases Carbon Dioxide ($\text{CO}_2$). |
| Light Target | Requires direct solar light energy inputs. | Functions continuously day and night without light inputs. |
| Cell Sites | Requires chlorophyll; occurs only in green plant cells. | Occurs within the mitochondria of all living cells. |
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