Biology Basics: General Science Notes for Railway (RRB)

Biology Basics – Study Notes

(For Railway RRB – General Science)

Feature	Explanation	Everyday Analogy
Growth	Things can become bigger over time.	A sapling turning into a tree.
Energy Use	Living things need food or light for energy.	A car needs gasoline.
Reproduction	They can make a copy of themselves.	Two parents having a child.
Response to Stimuli	They react to changes around them.	A plant bending toward sunlight.
Homeostasis	They keep internal conditions steady.	A thermostat keeping a room at 22 °C.

Very Simple Take‑away: If something can grow, eat, make copies, react, and keep itself steady, it’s alive.

All living things are made of cells.
A cell is like a tiny factory that does everything needed to stay alive.
Key parts (no fancy names):
- Outer wall – keeps the factory whole.
- Control room – tells the factory what to do (DNA).
- Workshops – build food (photosynthesis or food digestion).
- Waste bin – gets rid of trash.

Tiny Example:
A leaf cell collects sunlight and turns it into sugar, just like a factory turning raw materials into a finished product.

Cells that do similar tasks stick together.
Think of a team of workers all making the same product.
Types (very basic):
- Protective – skin cells form a shield.
- Transport – cells in blood carry oxygen.
- Support – bone cells keep the body strong.

A group of tissues that work together for one job.
Examples:
- Heart (pumps blood).
- Lungs (exchange gases).
- Stomach (breaks food).

Analogy: An organ is like a specific department in a company – each has a clear role.

Several organs that collaborate to perform a major function.
Major systems:
- Circulatory – moves blood everywhere.
- Digestive – breaks food into usable parts.
- Nervous – sends messages like a phone network.
- Respiratory – brings in fresh air, removes CO₂.

Tiny Example:
Your heart, blood vessels, and blood form the circulatory system – like a delivery network delivering nutrients.

Example: A sunflower is an organism; it grows from a seed, produces flowers, and eventually dies.

A set of organisms + their non‑living parts (air, water, soil).
Components:
- Living – plants, animals, microbes.
- Non‑living – light, air, water, minerals.
Energy Flow:
- Sunlight → plants → herbivores → carnivores → decomposers.

Tiny Example: A pond where fish, plants, insects, and water meet and share energy.

DNA is the instruction manual inside every cell.
Basic Idea: Parents give half of their instructions to their children.
Simple Trait Example:
- Eye color – parents’ genes decide whether the child gets blue or brown eyes.

No jargon tip: Think of genetics as a recipe book that you copy when you bake a cake. The recipe you copy depends on the books (genes) you have.

Populations change slowly over many generations.
Why it matters: It explains why species adapt to their environment.
Simple Example:
- Birds in a cold country develop thicker feathers to stay warm.

Analogy: Evolution is like a long‑term renovation of a house, where rooms are added or changed based on new needs.

System	Main Job
Digestive	Breaks food into energy.
Circulatory	Carries blood and nutrients.
Respiratory	Supplies oxygen, removes CO₂.
Nervous	Sends signals, controls actions.
Muscular	Moves the body.
Skeleton	Provides structure.
Immune	Fights infections.

Very Simple Take‑away: Your body is a busy city where each system is a department keeping everything running smoothly.