For Class 8, 9 & 10
Foundation - a strong base in Physics, Chemistry, Maths & Biology
Concept-first questions with clear model answers across all four subjects, aligned to NCERT. Start early, build the habit, and walk into your board exams, NEET and JEE already ahead.
Showing 7 questions in Biology for Class 10. Tap a card to reveal the answer.
BiologyLife ProcesseseasyHow is oxygen transported from the lungs to the tissues in human beings?
Reveal answer ↓
What it is
Oxygen rides on haemoglobin in red blood cells from the lungs to every tissue.
Answer
Oxygen diffuses from the air sacs (alveoli) of the lungs into the blood, where it binds to the red pigment haemoglobin in red blood cells to form oxyhaemoglobin. The blood carries it to the tissues, where oxygen is released for respiration. Haemoglobin makes this transport efficient because it has a high affinity for oxygen.
- •O2 diffuses from alveoli into blood
- •Binds to haemoglobin in RBCs
- •Carried as oxyhaemoglobin
- •Released at tissues for respiration
Why learn this
It's why anaemia leaves you tired and why blood is red - the body's oxygen delivery system.
💡 Memory trick
Haemoglobin is the 'oxygen taxi': O2 boards at the lungs, gets off at the tissues.
BiologyLife ProcesseseasyGive two differences between arteries and veins.
Reveal answer ↓
What it is
Arteries carry blood away from the heart under high pressure; veins bring it back and have valves.
Answer
Arteries carry blood away from the heart, usually oxygenated (except the pulmonary artery), have thick elastic walls and no valves because blood flows under high pressure. Veins carry blood towards the heart, usually deoxygenated (except the pulmonary vein), have thinner walls and contain valves to prevent the backflow of low-pressure blood.
- •Arteries: away from heart, thick walls, no valves, high pressure
- •Veins: towards heart, thin walls, valves present, low pressure
Why learn this
It's basic to understanding blood pressure, heart attacks and how injections and IV drips work.
💡 Memory trick
Arteries = Away from the heart; Veins have Valves to stop backflow.
BiologyControl and CoordinationmediumWhat is a reflex arc? Trace the path of a reflex action when you touch a hot object.
Reveal answer ↓
What it is
A reflex arc gives an instant, automatic response through the spinal cord - no thinking needed.
Answer
A reflex arc is the pathway followed by a nerve impulse during a reflex action, allowing a quick automatic response without conscious thought. When you touch a hot object, receptors in the skin send an impulse along a sensory neuron to the spinal cord; there a relay neuron passes it to a motor neuron, which carries the impulse to the muscles of the hand, causing you to pull your hand away instantly.
Receptor -> Sensory -> Spinal cord -> Motor -> Effector
- •Receptor -> sensory neuron -> spinal cord
- •Relay neuron -> motor neuron -> effector (muscle)
- •Fast, automatic, protects the body
- •Processed by spinal cord, not brain
Why learn this
It protects you in a split second (a hot pan, a sharp pin) before the brain even reacts.
💡 Memory trick
Receptor -> Sensory -> Spinal cord -> Motor -> Effector. The spinal cord shortcuts the brain.
BiologyHow do Organisms ReproducemediumWhy does sexual reproduction produce more variation than asexual reproduction?
Reveal answer ↓
What it is
Sexual reproduction mixes two parents' genes to create variety; asexual makes identical copies.
Answer
In sexual reproduction two parents contribute genes, and the mixing of DNA during the formation of gametes and their random combination at fertilisation creates new gene combinations in the offspring. In asexual reproduction a single parent produces genetically identical copies, so there is little variation. Greater variation gives species a better chance of surviving changes in the environment.
- •Two parents -> mixing of genes
- •Recombination during gamete formation + random fertilisation
- •Asexual -> identical copies, low variation
- •Variation aids survival and evolution
Why learn this
Variation is the raw material of evolution and why species survive changing conditions.
💡 Memory trick
Two parents = two gene decks shuffled = more variety. One parent = clones.
BiologyHeredity and EvolutionmediumIn a monohybrid cross between a tall pea plant (TT) and a short pea plant (tt), what is the ratio of tall to short plants in the F2 generation? Explain briefly.
Reveal answer ↓
What it is
Crossing two hybrids (Tt x Tt) gives a 3:1 tall-to-short ratio because T is dominant over t.
Answer
The F1 generation is all Tt (tall), because T is dominant over t. When F1 plants (Tt x Tt) are crossed, the F2 offspring are TT, Tt, Tt, tt. TT, Tt and Tt appear tall while tt is short, giving a phenotypic ratio of 3 tall : 1 short. The genotypic ratio is 1 TT : 2 Tt : 1 tt.
Tt x Tt -> 3 tall : 1 short (phenotype)
- •F1 all Tt (tall) - T dominant
- •F2 phenotypic ratio 3 tall : 1 short
- •F2 genotypic ratio 1:2:1
- •Illustrates Mendel's law of dominance and segregation
Why learn this
It's the foundation of genetics, inherited diseases and modern crop and gene science.
💡 Memory trick
Tt x Tt -> 3 tall : 1 short (phenotype), 1:2:1 (genotype). The classic Mendel 3:1.
BiologyLife ProcessesmediumWhat is photosynthesis? Write its balanced equation and the conditions needed.
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What it is
Photosynthesis is how green plants make their own food (glucose) from CO2 and water using sunlight.
Answer
Photosynthesis is the process by which green plants make their own food (glucose) from carbon dioxide and water using sunlight, releasing oxygen. The balanced equation is: 6CO2 + 6H2O -> C6H12O6 + 6O2. It requires chlorophyll (the green pigment), sunlight, carbon dioxide and water.
6CO2 + 6H2O -> C6H12O6 + 6O2
- •Green plants make glucose from CO2 and water using light
- •6CO2 + 6H2O -> C6H12O6 + 6O2
- •Needs chlorophyll, sunlight, CO2, water
- •Releases oxygen
Why learn this
It's the source of nearly all food and oxygen on Earth - the base of every food chain.
💡 Memory trick
6CO2 + 6H2O --(sunlight + chlorophyll)--> glucose + 6O2. Plants 'eat' light.
BiologyOur EnvironmentmediumWhat is a food chain? State the ten percent law of energy transfer.
Reveal answer ↓
What it is
A food chain shows who eats whom, and only about 10 percent of energy passes to the next level.
Answer
A food chain is a series of organisms through which energy and nutrients pass as one organism eats another, for example grass -> deer -> lion. The ten percent law states that only about 10 percent of the energy at one trophic level is passed on to the next level; the rest is lost mainly as heat. This is why food chains usually have only three or four links.
About 10% energy transferred per trophic level
- •Energy flows: producer -> herbivore -> carnivore
- •Only about 10% of energy passes to the next level
- •The rest is lost as heat
- •Limits food chains to 3-4 links
Why learn this
It explains why top predators are few and why pollutants concentrate up the chain.
💡 Memory trick
Only 10% of energy moves up each step (the '10% law'), so chains are short (3-4 links).