Plant Life, Cells, Human Body & Health (Biology) — Practice

Question 1

Write the word equation for photosynthesis. Name the organelle where this process occurs and the green pigment responsible.

Accepted Answer

Step 1 — Word equation: Carbon dioxide + Water → Glucose + Oxygen (in the presence of sunlight and chlorophyll).

Step 2 — Organelle: Photosynthesis occurs in the CHLOROPLASTS — found only in plant cells (and some algae).

Step 3 — Green pigment: CHLOROPHYLL — the green pigment inside chloroplasts that absorbs sunlight energy and uses it to power photosynthesis.

✦ Answer: CO₂ + H₂O → Glucose + O₂ (sunlight, chlorophyll). Location: CHLOROPLASTS. Pigment: CHLOROPHYLL.

Question 2

Name the four main parts of a flower and give the function of each. Which parts are male and which are female?

Accepted Answer

Step 1 — SEPAL: Green, leaf-like part. Function: PROTECTS the flower bud before it opens. Collectively called the calyx.

Step 2 — PETAL: Colourful, often scented part. Function: ATTRACTS pollinators (bees, butterflies, birds). Collectively called the corolla.

Step 3 — STAMEN (MALE part): Made of ANTHER (produces pollen grains) and FILAMENT (stalk holding the anther). Function: produces and releases pollen for reproduction.

Step 4 — PISTIL / CARPEL (FEMALE part): Made of STIGMA (sticky surface that receives pollen) + STYLE (tube) + OVARY (contains ovules/eggs). Function: receives pollen, fertilisation occurs here, ovary → fruit, ovules → seeds.

✦ Answer: Sepal = protects bud. Petal = attracts pollinators. Stamen (anther + filament) = MALE, produces pollen. Pistil (stigma + style + ovary) = FEMALE, receives pollen and produces fruit and seeds.

Question 3

Using the example of a mango, trace what happens from pollination to the formation of the mango fruit.

Accepted Answer

Step 1 — POLLINATION: Pollen grains from the anther of a mango flower are carried to the sticky STIGMA of another mango flower (cross-pollination by insects/wind).

Step 2 — GERMINATION of pollen: The pollen grain germinates on the stigma. A POLLEN TUBE grows down through the STYLE toward the OVARY.

Step 3 — FERTILISATION: The sperm cell from the pollen travels through the pollen tube and fuses with the OVUM (egg cell) inside the ovule. This forms a ZYGOTE.

Step 4 — FRUIT FORMATION: The fertilised OVARY grows and develops into the MANGO FRUIT (the fleshy part we eat). The fertilised OVULE develops into the MANGO SEED (the hard stone inside).

✦ Answer: Pollination → pollen on stigma → pollen tube grows → sperm + ovum = zygote → OVARY becomes MANGO FRUIT, OVULE becomes MANGO SEED.

Question 4

Who discovered the cell? When, how, and using what material did this discovery happen?

Accepted Answer

Step 1 — Who: ROBERT HOOKE, a British scientist.

Step 2 — When: 1665.

Step 3 — How: He used an early COMPOUND MICROSCOPE to examine a thin slice of CORK (dead plant tissue from bark).

Step 4 — What he saw: Tiny box-like compartments arranged in rows, resembling the small rooms (cellae) in a monastery. He named these compartments CELLS.

Step 5 — Note: Hooke saw dead cell walls only — not living cells. The discovery of living cells came later through Leeuwenhoek's work.

✦ Answer: ROBERT HOOKE discovered the cell in 1665, using a microscope to examine a CORK SLICE. He named the tiny box-like compartments 'cells' because they resembled monastery rooms (cellae in Latin).

Question 5

Draw a comparison table showing THREE differences between a plant cell and an animal cell.

Accepted Answer

Step 1 — Cell wall: Plant cell HAS a rigid cell wall (made of cellulose) outside the cell membrane. Animal cell has NO cell wall — only a flexible cell membrane.

Step 2 — Chloroplasts: Plant cell HAS chloroplasts (for photosynthesis). Animal cell has NO chloroplasts (cannot photosynthesise).

Step 3 — Vacuole: Plant cell HAS a large central VACUOLE (stores water, maintains cell shape). Animal cells have small or no vacuoles.

✦ Answer: 
| Feature | Plant Cell | Animal Cell |
|---------|-----------|-------------|
| Cell wall | Present (cellulose) | Absent |
| Chloroplasts | Present | Absent |
| Vacuole | Large central vacuole | Small or absent |

Question 6

Trace the journey of a piece of bread from the moment it enters your mouth to when its nutrients are absorbed into the blood. Name the organ responsible for final absorption.

Accepted Answer

Step 1 — MOUTH: Teeth break bread into smaller pieces (mechanical digestion). Saliva is mixed in — it contains the enzyme amylase, which begins breaking down STARCH into simpler sugars (chemical digestion).

Step 2 — OESOPHAGUS (food pipe): Swallowed food travels down the oesophagus by muscular contractions (peristalsis) to the stomach.

Step 3 — STOMACH: Gastric juice (hydrochloric acid + enzymes) continues digestion. Mainly PROTEINS are broken down here. Food is churned into a thick liquid (chyme).

Step 4 — SMALL INTESTINE: Bile (from liver, stored in gall bladder) digests FATS. Pancreatic enzymes break down carbohydrates and proteins further. This is where most NUTRIENT ABSORPTION happens through tiny finger-like projections called VILLI.

Step 5 — LARGE INTESTINE: WATER is absorbed. Remaining waste is compacted.

Step 6 — RECTUM → ANUS: Waste (faeces) is stored temporarily and expelled.

✦ Answer: Mouth (starch digestion) → Oesophagus → Stomach (protein digestion) → Small intestine (fat digestion + absorption through villi) → Large intestine (water absorption) → Rectum → Anus. Final absorption of nutrients: SMALL INTESTINE.

Question 7

Describe the path of air from the nose to where oxygen enters the blood. What are alveoli and why are they important?

Accepted Answer

Step 1 — Path of air: Nose (air filtered and warmed) → Trachea (windpipe) → Bronchi (trachea splits into left and right bronchus, one for each lung) → Bronchioles (smaller branches) → Alveoli (tiny air sacs at the end of bronchioles).

Step 2 — What are alveoli: ALVEOLI are millions of tiny, thin-walled air sacs in the lungs. They are surrounded by a network of tiny blood vessels (capillaries).

Step 3 — Why they are important: Gas exchange happens in the alveoli. Oxygen from inhaled air passes through the thin alveolar walls into the bloodstream (capillaries). Carbon dioxide from the blood passes into the alveoli and is exhaled.

Step 4 — Why the design matters: Millions of alveoli provide an enormous surface area (about the size of a tennis court in both lungs combined!) for gas exchange — making breathing highly efficient.

✦ Answer: Air path: Nose → Trachea → Bronchi → Bronchioles → Alveoli. Alveoli = tiny air sacs surrounded by capillaries, where O₂ passes into blood and CO₂ passes out. Millions of alveoli = huge surface area = efficient gas exchange.

Question 8

Distinguish communicable and non-communicable diseases. Give TWO examples of each. Why do we use vaccines for communicable but not non-communicable diseases?

Accepted Answer

Step 1 — COMMUNICABLE diseases: Caused by PATHOGENS (bacteria, viruses, fungi, parasites). SPREAD from person to person through air, water, touch, or vectors (mosquitoes). Examples: Tuberculosis (bacteria, spread through air), Typhoid (bacteria, spread through contaminated water), COVID-19 (virus, spread through air droplets).

Step 2 — NON-COMMUNICABLE diseases: NOT caused by pathogens. NOT spread from person to person. Caused by lifestyle factors, genetics, or ageing. Examples: Diabetes (body cannot regulate blood sugar), Heart disease (blocked blood vessels from poor diet/lifestyle), Cancer (abnormal cell growth), Asthma (chronic lung inflammation).

Step 3 — Why vaccines work for communicable but not non-communicable: VACCINES train the immune system to recognise and attack a SPECIFIC pathogen. Since non-communicable diseases are NOT caused by pathogens (no germ to fight), there is no pathogen for the immune system to target. Vaccines are pointless against diabetes or cancer caused by lifestyle — prevention requires diet, exercise, and health monitoring instead.

✦ Answer: Communicable = spread by pathogens (TB, COVID-19). Non-communicable = not contagious, caused by lifestyle/genetics (diabetes, cancer). Vaccines train immune system against specific pathogens — useless against non-communicable diseases because there is no germ to target.

Practice — Plant Life, Cells, Human Body & Health (Biology)

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