Aswajith

🐸 Amphibians

Amphibians are animals that live two kinds of lives — one in water and one on land.The word “amphibian” means “double life.”

🧬 how they grow

When they are born, they start life in water as larvae (like tadpoles).They breathe with gills like fish and swim using a tail.Then, as they grow up, they go through a change called metamorphosis —their gills turn into lungs, their tails shrink, and they grow legs for land.

💧 why they need water

Even when they live on land, their skin must stay wet.Their skin helps them breathe oxygen directly from air or water.If their skin dries, they can suffocate.That’s why you’ll see frogs, salamanders, and newts in damp places.

🫀 Circulation means blood movement in the body.

It’s how oxygen, food, and waste move around using the heart and blood vessels.

But not all animals have the same kind of circulation —some have single circulation, others have double circulation.

🐟 Single Circulation (in fish)

Fish have a two-chambered heart — one atrium and one ventricle.Blood goes like this:

Heart → Gills → Body → Back to Heart

Inside every living cell, there is a kind of instruction book that controls everything the organism does — how it looks, grows, and functions.That instruction book is made of DNA, arranged into genes, and packed into chromosomes.

🧬 DNA (Deoxyribonucleic Acid)

DNA is the molecule of life.It’s a long, spiral-shaped molecule that looks like a twisted ladder, called a double helix.Each “rung” of the ladder is made from base pairs — adenine (A), thymine (T), cytosine (C), and guanine (G).The order of these bases forms a code, just like letters in a language.

That code tells the cell how to build proteins — and proteins are what make up your muscles, skin, hair, and even enzymes that run your body’s chemistry.

So, DNA is basically a chemical code that stores genetic information.

🧩 Gene

 Means grouping animals based on how they are built, how they live, and how they are related. Scientists do this to understand the huge variety of animals on Earth and their connections through evolution.

All animals are placed under the Kingdom Animalia, and from there, they are divided step by step into smaller groups: Phylum, Class, Order, Family, Genus, and Species. Each step shows how closely animals are related.

The first big division inside the animal kingdom is between invertebrates and vertebrates.

Invertebrates are animals without a backbone. They are the oldest and most common kind, making up about 95% of all animal species. They include insects, worms, jellyfish, snails, corals, and spiders. Many of them have soft bodies, and some are protected by shells or hard coverings like exoskeletons.

Vertebrates are animals with a backbone. They include fish, amphibians, reptiles, birds, and mammals. They have an internal skeleton made of bone or…