Biology — Transport, Reproduction, Ecosystems & Body Systems
1. Transport in Plants
Xylem — Water and Minerals UP
Tubes made of DEAD cells. Transports WATER and DISSOLVED MINERALS from ROOTS → STEM → LEAVES. Movement: ONE WAY (upward only).
Phloem — Food in ALL Directions
Tubes made of LIVING cells. Transports FOOD (sucrose/glucose — made in leaves by photosynthesis) to ALL PARTS of the plant — roots, stems, fruits, growing tips. Movement: BOTH UP AND DOWN.
Transpiration — The 'Pull'
Water EVAPORATES from leaves through STOMATA. This creates a 'SUCTION PULL' that draws water up from the roots through the xylem. 'Transpiration is the ENGINE that drives water transport in plants.'
2. Reproduction in Plants and Animals
Asexual Reproduction (One Parent — Offspring are CLONES)
| Method | Example |
|---|---|
| Binary Fission | Amoeba, bacteria (splitting into two) |
| Budding | Yeast, Hydra |
| Fragmentation | Spirogyra (algae). Starfish. |
| Vegetative Propagation | Plants — stem cutting (rose), tuber (potato), runner (strawberry) |
Sexual Reproduction (Two Parents — VARIATION)
- Plants: Flowers contain STAMENS (male — pollen) and PISTIL (female — ovules). Pollination → Fertilisation → Seed → Fruit.
- Animals: Fusion of MALE GAMETE (sperm) and FEMALE GAMETE (egg/ovum) → ZYGOTE → EMBRYO → OFFSPRING.
3. Ecosystems
What Is an Ecosystem?
A COMMUNITY of LIVING organisms interacting with each other and their PHYSICAL ENVIRONMENT.
Components
- BIOTIC (Living): Producers (green plants). Consumers (animals — herbivores, carnivores, omnivores). Decomposers (bacteria, fungi — break down dead matter).
- ABIOTIC (Non-living): Sunlight, water, air, soil, temperature.
Food Chains and Food Webs
- Food Chain: A LINEAR sequence. Grass → Grasshopper → Frog → Snake → Eagle.
- Food Web: INTERCONNECTED food chains. An organism may eat (or be eaten by) MULTIPLE others. 'The web is more REALISTIC than the chain. Energy flows through the ecosystem in a complex network.'
Ecological Pyramids
- Pyramid of ENERGY: ALWAYS upright. Energy DECREASES at each trophic level (~10% transfers to the next level).
- 'This loss of energy explains why there are fewer TOP predators than herbivores.'
4. The Circulatory System (Cardiovascular System)
Components
- Heart: The PUMP. Four chambers: 2 atria (upper). 2 ventricles (lower).
- Blood Vessels: Arteries (carry blood AWAY from heart — thick, elastic). Veins (carry blood BACK to heart — thinner, have VALVES). Capillaries (TINY — one cell thick — where exchange of gases and nutrients occurs).
Blood
- Red Blood Cells (RBCs) : Carry OXYGEN. Contain HAEMOGLOBIN (iron-containing protein).
- White Blood Cells (WBCs) : FIGHT INFECTION. Part of the immune system.
- Platelets: Help in BLOOD CLOTTING.
- Plasma: LIQUID part. Transports nutrients, hormones, waste.
Double Circulation
Blood passes through the heart TWICE in one complete circuit: Heart → Lungs (pulmonary — picks up oxygen) → Heart → Body (systemic — delivers oxygen) → Back to heart.
5. The Endocrine System (Chemical Coordination)
How It Works
GLANDS release HORMONES (chemical messengers) directly into the BLOOD. Hormones travel to TARGET ORGANS and regulate their functions.
| Gland | Hormone(s) | Main Function |
|---|---|---|
| Pituitary | Growth hormone, many others | 'Master Gland' — controls all other glands |
| Thyroid | Thyroxine | Controls METABOLISM rate. Needs IODINE. |
| Pancreas | Insulin | Regulates BLOOD SUGAR. Deficiency → DIABETES. |
| Adrenal | Adrenaline | 'Fight or flight' — prepares body for EMERGENCY |
6. Food Production
Agriculture and Animal Husbandry
- Agriculture: Growing crops. Animal husbandry: Rearing livestock.
- Green Revolution: HYV seeds + fertilisers + irrigation → DRAMATIC increase in food grain production. India became self-sufficient. BUT: environmental costs — water depletion, chemical pollution.
- White Revolution (Operation Flood) : India = world's #1 milk producer.
Sustainable Practices
- Organic farming. Crop rotation. Integrated pest management. 'Feed the world WITHOUT destroying the soil, water, and biodiversity that sustain it.'
