I. Choose the Best Answer (MCQs)
Q1. Tough and thick white sheath protecting inner parts of the eye is
- (a) Sclera (b) Cornea (c) Iris (d) Retina
Q2. Maintenance of constant internal environment is called
- (a) Homeostasis (b) Respiration (c) Metabolism (d) Osmosis
Q3. In the absence of oxygen, glucose breaks down into
- (a) Lactic acid (b) Ethanol (c) Carbon dioxide (d) Water
Q4. Specialized cells that can transform into any kind of cell are called
- (a) Red blood cells (b) Stem cells (c) White blood cells (d) Nerve cells
Q5. The process of air passing in and out of the lungs is called
- (a) Respiration (b) Breathing (c) Inhalation (d) Exhalation
Q6. In osmosis, water moves from
- (a) Higher to lower concentration (b) Lower to higher concentration
- (c) Equal concentration (d) None of the above
Q7. Erythrocyte placed in ___ solution (lesser solute concentration) will swell
- (a) Hypotonic (b) Hypertonic (c) Isotonic (d) None
II. Fill in the Blanks
1. Cell is the structural and functional unit of living organisms. 2. The largest cell is the egg of an Ostrich. 3. Fermentation is a good example for anaerobic respiration. 4. Optic nerve is located behind the retina. 5. The size of cells is measured in units of Microns (micrometres). 6. The process of breaking down food to release energy is called respiration. 7. The exchange of gases in lungs takes place in alveoli. 8. Anabolism is the process of building up complex substances from simpler ones. 9. Catabolism is the process of breaking down complex substances into simpler ones. 10. The lens of the eye is located behind the iris/pupil.
III. True or False
IV. Match the Following
| Column A | Column B | Answer |
|---|---|---|
| Cell | Tissue | Basic unit |
| Tissue | Organ | Group of similar cells |
| Organ | Organ system | Group of tissues |
| Organ system | Organism | Group of organs |
Arrangement in sequence: Cell → Tissue → Organ → Organ System → Organism
V. Very Short Answers
Q1. What is the structural and functional unit of life? Answer: The cell.
Q2. Name the largest cell. Answer: The egg of an ostrich (about 170 mm in diameter).
Q3. What is fermentation? Answer: Fermentation is an anaerobic process where microorganisms like yeast convert sugars into alcohol and carbon dioxide, releasing a small amount of energy.
Q4. What is the function of alveoli? Answer: Alveoli are tiny air sacs in the lungs where the exchange of oxygen and carbon dioxide takes place between air and blood.
Q5. What are stem cells? Answer: Specialized cells that can transform into any kind of cell in the body. They are found in bone marrow, umbilical cord blood, and embryos.
Q6. What is homeostasis? Answer: The maintenance of a constant internal environment in the body despite changes in external conditions.
Q7. Name the three types of muscle tissue. Answer: Striated (voluntary/skeletal), Non-striated (smooth/involuntary), and Cardiac muscle.
Q8. What is the function of the iris? Answer: The iris controls the size of the pupil, regulating the amount of light entering the eye.
VI. Short Answers
Q1. What is cell differentiation? Answer: Cell differentiation is the process by which unspecialized cells (stem cells) transform into specialized cells with specific functions. For example, stem cells differentiate into nerve cells, muscle cells, or blood cells depending on the body's needs.
Q2. What are the types of tissues? Give examples. Answer: 1. Epithelial tissue — Covers body surfaces and lines cavities (e.g., skin, lining of digestive tract) 2. Connective tissue — Connects and supports body parts (e.g., bone, cartilage, blood) 3. Muscular tissue — Enables movement (e.g., skeletal muscle, cardiac muscle, smooth muscle) 4. Nervous tissue — Transmits signals (e.g., brain, spinal cord, nerves)
Q3. Differentiate between aerobic and anaerobic respiration.
| Feature | Aerobic Respiration | Anaerobic Respiration |
|---|---|---|
| Oxygen required | Yes | No |
| End products | CO2 + H2O | Lactic acid (in muscles) or Ethanol + CO2 (in yeast) |
| Energy released | 38 ATP | 2 ATP |
| Location | Mitochondria | Cytoplasm |
| Efficiency | High | Low |
Q4. Explain osmosis with RBC examples. Answer: Osmosis is the movement of water through a semi-permeable membrane from a region of higher water concentration to lower water concentration.
- In hypotonic solution (less solute outside): Water enters RBC, cell swells and may burst (haemolysis).
- In hypertonic solution (more solute outside): Water leaves RBC, cell shrinks (crenation).
- In isotonic solution (equal concentration): No net water movement; cell maintains its shape.
Q5. Differentiate between inhalation and exhalation.
| Feature | Inhalation | Exhalation |
|---|---|---|
| Diaphragm | Contracts and flattens | Relaxes and becomes dome-shaped |
| Rib cage | Moves upward and outward | Moves downward and inward |
| Lung volume | Increases | Decreases |
| Air pressure in lungs | Decreases (air rushes in) | Increases (air rushes out) |
| Muscles | Intercostal muscles contract | Intercostal muscles relax |
Q6. What is metabolism? Differentiate between anabolism and catabolism. Answer: Metabolism is the sum of all chemical reactions occurring in a living organism to maintain life.
| Feature | Anabolism | Catabolism |
|---|---|---|
| Definition | Building up complex substances from simpler ones | Breaking down complex substances into simpler ones |
| Energy | Requires energy (endergonic) | Releases energy (exergonic) |
| Example | Photosynthesis, protein synthesis | Respiration, digestion |
Q7. Describe the structure of the human eye. Answer: The human eye is a spherical organ composed of:
- Sclera — Tough, white outer coat that protects the eye.
- Cornea — Transparent front part of the sclera that allows light to enter.
- Iris — Coloured part that controls pupil size and light entry.
- Pupil — Opening in the iris through which light passes.
- Lens — Behind the pupil; focuses light on the retina.
- Retina — Light-sensitive layer at the back with rods (dim light) and cones (colour).
- Optic nerve — Transmits visual signals from retina to the brain.
- Aqueous humour — Clear fluid in front of the lens.
- Vitreous humour — Jelly-like substance behind the lens.
VII. Detailed Answers
Q1. Compare the human eye with a camera.
| Feature | Human Eye | Camera |
|---|---|---|
| Lens | Adjustable convex lens | Fixed convex lens |
| Aperture | Pupil (controlled by iris) | Diaphragm (adjustable opening) |
| Film/Sensor | Retina (rods and cones) | Film or digital sensor |
| Focusing | Accommodation (ciliary muscles change lens shape) | Manual or auto-focus mechanism |
| Light entry | Cornea and pupil | Lens and aperture |
| Image formed | Real, inverted on retina | Real, inverted on film/sensor |
Q2. Explain the mechanism of breathing. Answer: Breathing involves two processes:
Inhalation (inspiration): 1. Diaphragm contracts and flattens. 2. Intercostal muscles contract, moving the rib cage upward and outward. 3. Chest cavity enlarges, reducing pressure inside the lungs. 4. Air from outside rushes into the lungs to equalize pressure.
Exhalation (expiration): 1. Diaphragm relaxes and returns to dome shape. 2. Intercostal muscles relax, moving the rib cage downward and inward. 3. Chest cavity decreases, increasing pressure inside the lungs. 4. Air is pushed out of the lungs.
Q3. What is osmoregulation? How does it maintain homeostasis? Answer: Osmoregulation is the process of maintaining the proper balance of water and salts (osmotic pressure) in the body.
In humans, the kidneys play a major role:
- When the body has excess water, the kidneys produce dilute urine to remove the surplus.
- When the body is dehydrated, the kidneys produce concentrated urine to conserve water.
- This helps maintain homeostasis by keeping the internal fluid balance stable despite changes in external conditions.
Other mechanisms include sweating (loss of water and salts through skin) and the action of antidiuretic hormone (ADH) from the pituitary gland.
Q4. Write a note on the levels of organisation in living organisms. Answer: Living organisms show a hierarchy of organisation:
1. Cell — The basic structural and functional unit of life (e.g., nerve cell, muscle cell). 2. Tissue — A group of similar cells performing a specific function (e.g., muscular tissue, nervous tissue). 3. Organ — A group of tissues working together for a specific function (e.g., heart, stomach, eye). 4. Organ System — A group of organs working together (e.g., digestive system, respiratory system). 5. Organism — A complete living individual made up of all organ systems functioning together.
This is called the hierarchy of organisation: Cell → Tissue → Organ → Organ System → Organism.
Q5. Explain aerobic and anaerobic respiration with equations. Answer: Aerobic Respiration: Glucose is completely broken down in the presence of oxygen to release energy. C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy (38 ATP)
Anaerobic Respiration: Glucose is partially broken down without oxygen, producing less energy.
In muscle cells: C6H12O6 → 2C3H6O3 (Lactic acid) + Energy (2 ATP)
In yeast (fermentation): C6H12O6 → 2C2H5OH (Ethanol) + 2CO2 + Energy (2 ATP)
Higher Order Thinking Questions
Q1. Why do athletes experience muscle cramps after intense exercise? Answer: During intense exercise, muscles require more oxygen than the body can supply. This leads to anaerobic respiration in muscle cells, producing lactic acid. The accumulation of lactic acid causes muscle cramps and fatigue. Resting allows oxygen to reach the muscles and break down the lactic acid.
Q2. Why should we not drink seawater when thirsty? Answer: Seawater is hypertonic (high salt concentration). Drinking it would draw water out of cells by osmosis, causing dehydration instead of relieving thirst. The kidneys would need more water to excrete the excess salt than the seawater provides.
Q3. How does the eye adjust to see objects at different distances? Answer: The ciliary muscles change the shape of the lens — for near objects, the lens becomes thicker (more curved); for distant objects, the lens becomes thinner (less curved). This process is called accommodation.
Common Mistakes
- Saying tissue is the basic unit of life: The cell is the basic unit; tissues are groups of similar cells.
- Confusing breathing with respiration: Breathing is the physical process of air movement; respiration is the chemical process of energy release.
- Confusing hypotonic and hypertonic: Hypotonic = less solute outside (cell swells); Hypertonic = more solute outside (cell shrinks).
- Confusing anabolism with catabolism: Anabolism builds up (requires energy); catabolism breaks down (releases energy).
- Saying aerobic respiration produces 2 ATP: Aerobic respiration produces 38 ATP; anaerobic produces only 2 ATP.
- Confusing aqueous humour with vitreous humour: Aqueous humour is in front of the lens; vitreous humour is behind the lens.
Exam Checklist
- [ ] Can you describe the hierarchy: Cell → Tissue → Organ → Organ System → Organism?
- [ ] Can you define and give examples of cell differentiation?
- [ ] Can you explain osmosis with RBC in hypotonic, hypertonic, and isotonic solutions?
- [ ] Can you differentiate between aerobic and anaerobic respiration with equations?
- [ ] Can you explain the mechanism of breathing (inhalation and exhalation)?
- [ ] Can you describe the structure of the human eye and compare it with a camera?
- [ ] Can you define homeostasis and osmoregulation?
- [ ] Can you differentiate between anabolism and catabolism?
- [ ] Can you explain what stem cells are and their significance?
- [ ] Can you list and describe the four types of tissues?