Biology

---
name: biology
description: >-
  CBSE Grade 10 Biology — Life Processes, Control & Coordination, Reproduction, Heredity, Environment.
  Activate for biology concepts, diagrams, processes, and board exam preparation.
---

# Biology — CBSE Grade 10 Science

## Syllabus Coverage (2026–27)

| Unit | Chapters | Marks |
|------|----------|-------|
| II. World of Living | Ch 5: Life Processes | 25 |
| | Ch 6: Control and Coordination | (combined) |
| | Ch 7: How do Organisms Reproduce? | |
| | Ch 8: Heredity | |
| V. Natural Resources | Ch 13: Our Environment | 5 |
| **Biology Total** | **5 Chapters** | **~30** |

---

## Chapter 5: Life Processes

### Key Concepts

**Nutrition:**
- **Autotrophic nutrition** (Photosynthesis):
  - 6CO₂ + 6H₂O →sunlight, chlorophyll→ C₆H₁₂O₆ + 6O₂
  - Steps: Light reaction → Dark reaction (Calvin cycle)
  - Raw materials: CO₂ (from stomata), H₂O (from roots), Sunlight, Chlorophyll
- **Heterotrophic nutrition**: Holozoic, Saprophytic, Parasitic
- **Human Digestive System** (DIAGRAM MUST):
  - Mouth → Oesophagus → Stomach → Small intestine → Large intestine → Anus
  - Salivary amylase (starch → maltose, pH ~6.8)
  - Pepsin (proteins → peptones, pH ~2, HCl in stomach)
  - Bile (emulsification of fats, from liver)
  - Pancreatic enzymes: trypsin (proteins), lipase (fats), amylase (starch)
  - Villi in small intestine → absorption (large surface area)

**Respiration:**
- Aerobic: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38 ATP (mitochondria)
- Anaerobic (yeast): C₆H₁₂O₆ → 2C₂H₅OH + 2CO₂ + 2 ATP
- Anaerobic (muscles): C₆H₁₂O₆ → 2C₃H₆O₃ (lactic acid) + 2 ATP
- **Human Respiratory System** (DIAGRAM MUST):
  - Nostrils → Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli
  - Alveoli: thin walls, rich blood supply, large surface area → gas exchange

**Transportation:**
- **Human Heart** (DIAGRAM MUST — 4 chambers):
  - Right atrium → Right ventricle → Pulmonary artery → Lungs
  - Lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta → Body
  - Double circulation: pulmonary + systemic
  - Valves prevent backward flow
- **Blood**: RBCs (carry O₂), WBCs (fight infection), Platelets (clotting), Plasma (liquid)
- **Blood vessels**: Arteries (thick walls, high pressure), Veins (valves, low pressure), Capillaries (thin walls, exchange)
- **Transportation in plants**:
  - Xylem: water + minerals (upward) — transpiration pull, root pressure
  - Phloem: food (sugars) — translocation (bidirectional, uses ATP)

**Excretion:**
- **Human Excretory System** (DIAGRAM MUST):
  - Kidneys → Ureters → Urinary bladder → Urethra
  - **Nephron** (functional unit, DIAGRAM MUST):
    - Bowman's capsule → Proximal tubule → Loop of Henle → Distal tubule → Collecting duct
    - Filtration → Reabsorption → Secretion → Urine
  - Urine composition: water, urea, uric acid, salts
- **Excretion in plants**: O₂ (day), CO₂ (night), excess water (transpiration), resins/gums stored in old xylem

### Diagram Checklist (Board Exam)
- [ ] Human digestive system with labels
- [ ] Human respiratory system with alveoli detail
- [ ] Human heart (cross-section, 4 chambers, blood flow arrows)
- [ ] Nephron structure
- [ ] Cross-section of leaf (stomata, guard cells)

---

## Chapter 6: Control and Coordination

### Key Concepts

**Nervous System:**
- **Neuron** (DIAGRAM MUST): Cell body → Dendrite → Axon → Axon terminal → Synapse
- **Reflex arc**: Receptor → Sensory nerve → Spinal cord → Motor nerve → Effector
- **Types**: Voluntary (cerebrum), Involuntary (medulla), Reflex (spinal cord)
- **Human Brain** (DIAGRAM MUST):
  - Cerebrum: thinking, memory, sensation
  - Cerebellum: balance, posture
  - Medulla oblongata: breathing, heartbeat, blood pressure
  - Pons: relay between cerebrum and cerebellum

**Hormonal System (Endocrine Glands):**

| Gland | Hormone | Function |
|-------|---------|----------|
| Pituitary | Growth hormone | Growth of bones and muscles |
| Thyroid | Thyroxine | Metabolism (needs iodine) |
| Pancreas | Insulin | Lowers blood sugar (diabetes if deficient) |
| Pancreas | Glucagon | Raises blood sugar |
| Adrenal | Adrenaline | Fight-or-flight response |
| Testes | Testosterone | Male secondary sexual characters |
| Ovaries | Estrogen | Female secondary sexual characters |

**Plant Hormones:**

| Hormone | Function |
|---------|----------|
| Auxin | Cell elongation, phototropism, gravitropism |
| Gibberellin | Stem elongation, seed germination |
| Cytokinin | Cell division, delays aging |
| Abscisic acid | Growth inhibitor, wilting, dormancy |
| Ethylene | Fruit ripening |

**Tropic Movements in Plants:**
- Phototropism: response to light (shoots +ve, roots -ve)
- Geotropism: response to gravity (roots +ve, shoots -ve)
- Hydrotropism: response to water (roots +ve)
- Chemotropism: response to chemicals (pollen tube towards ovule)
- Thigmotropism: response to touch (tendrils)

---

## Chapter 7: How do Organisms Reproduce?

### Key Concepts

**Asexual Reproduction:**
- Fission: Binary (Amoeba), Multiple (Plasmodium)
- Budding: Hydra, Yeast
- Spore formation: Rhizopus
- Fragmentation: Spirogyra
- Regeneration: Planaria
- Vegetative propagation: runners (grass), tubers (potato), bulbs (onion), grafting, layering, cutting

**Sexual Reproduction in Flowering Plants:**
- **Flower structure** (DIAGRAM MUST):
  - Sepals (calyx) → Petals (corolla) → Stamens (androecium: anther + filament) → Pistil (gynoecium: stigma + style + ovary)
- Pollination: Self-pollination vs Cross-pollination
- Fertilization: Pollen grain → Pollen tube → Ovule → Fusion of gametes
- Post-fertilization: Ovule → Seed, Ovary → Fruit

**Sexual Reproduction in Humans:**
- **Male reproductive system** (DIAGRAM): Testes → Vas deferens → Seminal vesicles → Prostate → Urethra → Penis
- **Female reproductive system** (DIAGRAM): Ovaries → Fallopian tubes → Uterus → Vagina
- Fertilization occurs in fallopian tube
- Implantation in uterus wall
- Placenta: provides nutrition, O₂ to embryo; removes wastes
- Menstruation: 28-day cycle; uterine lining sheds if no fertilization

**Contraception Methods:**
- Barrier: Condom, diaphragm
- Chemical: Oral pills (hormonal)
- Intrauterine device: Copper-T
- Surgical: Vasectomy (male), Tubectomy (female)

---

## Chapter 8: Heredity

### Key Concepts
- **Genetics**: study of inheritance
- **Gene**: unit of inheritance, part of DNA on chromosome
- **Alleles**: different forms of a gene (dominant T, recessive t)
- **Mendel's Laws**:
  - Law of Dominance: dominant allele expresses in F₁
  - Law of Segregation: alleles separate during gamete formation
  - Law of Independent Assortment: genes on different chromosomes sort independently

### Mendel's Cross (MUST know)
```
MONOHYBRID CROSS (one trait):
  Parents: TT (tall) × tt (short)
  F₁:      Tt (all tall) — dominant trait expressed
  F₁ × F₁: Tt × Tt
  F₂:      TT : Tt : Tt : tt = 3 Tall : 1 Short
  Genotypic ratio: 1:2:1
  Phenotypic ratio: 3:1

DIHYBRID CROSS (two traits):
  Parents: RRYY × rryy
  F₁:      RrYy (all round yellow)
  F₁ × F₁: RrYy × RrYy
  F₂ Phenotypic ratio: 9:3:3:1
    9 Round Yellow : 3 Round Green : 3 Wrinkled Yellow : 1 Wrinkled Green
```

### Sex Determination
```
Humans: XX-XY system
  Female: XX (homogametic)
  Male: XY (heterogametic)
  Father determines sex of child:
    X sperm + X egg → XX (girl)
    Y sperm + X egg → XY (boy)
  Probability: 50% boy, 50% girl
```

### Evolution Concepts
- **Acquired characters** are NOT inherited (Lamarck was wrong)
- **Natural selection**: organisms best adapted survive (Darwin)
- **Homologous organs**: same structure, different function (human hand, whale flipper, bat wing)
- **Analogous organs**: different structure, same function (bird wing, insect wing)
- **Fossils**: preserved remains, evidence of evolution
- **Speciation**: geographical isolation → genetic drift → new species

---

## Chapter 13: Our Environment

### Key Concepts
- **Ecosystem**: biotic + abiotic components interacting
- **Food chain**: Grass → Grasshopper → Frog → Snake → Hawk
- **Food web**: interconnected food chains
- **Trophic levels**: Producers (T1) → Primary consumers (T2) → Secondary consumers (T3) → Tertiary consumers (T4)
- **10% Law**: Only 10% energy transfers to next trophic level
- **Biological magnification**: concentration of toxins increases at higher trophic levels
- **Ozone layer**: O₃ in stratosphere, protects from UV; depleted by CFCs
- **Biodegradable waste**: broken down by microorganisms (paper, food waste)
- **Non-biodegradable waste**: NOT broken down (plastic, glass, metal)

### Key Formulas
```
10% LAW:
  If producers have 10,000 J energy:
  T1 (Producers): 10,000 J
  T2 (Herbivores): 1,000 J
  T3 (Carnivores): 100 J
  T4 (Top carnivores): 10 J

OZONE FORMATION:
  O₂ →UV→ O + O (dissociation)
  O + O₂ → O₃ (ozone formation)

OZONE DEPLETION:
  CFCs →UV→ Cl + other fragments
  Cl + O₃ → ClO + O₂
  ClO + O₃ → Cl + 2O₂ (Cl acts as catalyst)
```

---

## High-Yield Topics (495+ Strategy)
1. **Life Processes (Digestion, Heart, Nephron)** — 5M diagram-based LA guaranteed
2. **Heredity (Mendel's crosses)** — 3-5M cross problems
3. **Reproduction** — 3-5M flower structure / human reproductive system
4. **Control and Coordination** — 3M hormones table, reflex arc
5. **Environment** — 2-3M food chain / 10% law

## Common Mistakes to Avoid
1. Not drawing diagrams neatly with ALL labels
2. Confusing xylem (water, dead cells, upward) with phloem (food, living cells, bidirectional)
3. Mixing up arteries (away from heart) and veins (towards heart)
4. Wrong genotypic vs phenotypic ratios
5. Forgetting that father determines sex (not mother)
6. Not mentioning "10% law" by name in energy flow questions

## Answer Writing Framework for Biology
1. **Diagrams = marks**: Draw first, then explain. Label every part.
2. **Use biological terms**: "peristalsis" not "pushing food", "transpiration" not "water loss"
3. **For process questions**: Write steps in numbered sequence
4. **For comparison**: Use a table format (Arteries vs Veins, Xylem vs Phloem)
5. **Mendel crosses**: Always draw the cross diagram with Punnett square
6. **Define, then explain**: Start with definition, then elaborate

## Internal Assessment Notes
| Component | Details |
|-----------|---------|
| Practical Exam | Experiments: stomata observation, CO₂ in exhaled air, germination, plant & animal specimens |
| Practical viva | Focus on Life Processes and Reproduction experiments |
| Projects | Biodiversity, pollution, genetics project — present neatly with diagrams |