RRB Group D · Bite-size lessons

Life Sciences (Biology)

About 7 min · General Science · English

Time worked out from the lesson's 461 words at 150 words a minute, plus a minute for each question.

This topic tests your understanding of living organisms, their structure, function, classification and interactions with the environment. Questions are fact-based and drawn from NCERT Class 9–10 Biology, so mastering core concepts from cell biology, human physiology, plant biology, heredity and ecology is essential.

Key ideas

• Cell as the unit of life: All living organisms are made of cells. Prokaryotic cells (bacteria) lack a nucleus; eukaryotic cells (animals, plants, fungi) have a membrane-bound nucleus and organelles like mitochondria, ribosomes, endoplasmic reticulum, Golgi apparatus and lysosomes.
• Five-kingdom classification: Organisms are grouped into Monera (bacteria), Protista (algae, protozoans), Fungi (yeasts, moulds), Plantae (mosses to flowering plants) and Animalia (sponges to mammals). This classification is based on cell structure, mode of nutrition and body organization.
• Photosynthesis and respiration: Green plants synthesize glucose from CO₂ and water using sunlight (photosynthesis: 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂). All cells release energy by breaking down glucose in the presence of oxygen (aerobic respiration) or without it (anaerobic respiration/fermentation).
• Human organ systems: The body has digestive, circulatory, respiratory, excretory, nervous, endocrine, reproductive, skeletal and muscular systems working in coordination. For example, the heart pumps oxygenated blood via arteries to tissues, and deoxygenated blood returns via veins to the heart, which pumps it to the lungs.
• Heredity and DNA: Traits pass from parents to offspring through genes located on chromosomes in the nucleus. DNA (deoxyribonucleic acid) is the hereditary material. Gregor Mendel's experiments with pea plants established the laws of inheritance (dominance, segregation, independent assortment).

Watch out for

• Confusing mitochondria and chloroplast Wrong: "Chloroplasts release energy from food." Correct: Chloroplasts perform photosynthesis (making food); mitochondria perform respiration (releasing energy from food). Chloroplasts are only in plant cells; mitochondria are in both plant and animal cells.
• Mixing up xylem and phloem Wrong: "Phloem transports water from roots to leaves." Correct: Xylem transports water and minerals upward; phloem transports food (sugars) from leaves to all parts in both directions.
• Saying all diseases are caused by bacteria Wrong: "Malaria is caused by a bacterium." Correct: Malaria is caused by Plasmodium, a protozoan parasite. Diseases can be viral (AIDS, flu), bacterial (TB, typhoid), fungal (ringworm) or protozoan (malaria, amoebic dysentery).

Quick reference

• Cell powerhouse: Mitochondria (respiration, ATP production).
• Green pigment: Chlorophyll in chloroplasts enables photosynthesis.
• Human blood: 4 groups (A, B, AB, O); O is universal donor, AB universal recipient.
• Mendel's organism: Garden pea (Pisum sativum); established laws of heredity.
• Deficiency diseases: Vitamin A → night blindness; C → scurvy; D → rickets; B1 → beriberi; iron → anemia; iodine → goiter.

Check yourself: 3 questions

This lesson is cut from the topic's note, not rewritten. Fact-checked on 21 Oct 2026: an AI-assisted check of this note against cited sources; the errors it found were corrected that day. Some errors may remain. The questions are from Shishya's validated question bank.

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