Niveditha

The human eye is a spherical, hollow, sensory organ specialized to receive light, focus it, convert it into electrical signals, and send those signals to the brain. Its structure can be understood by dividing it into three main layers and then looking at the structures inside.

OUTER LAYER (Protective Layer)

Cornea

The cornea is the transparent, curved front portion of the eye that allows light to enter. Its curvature bends (refracts) incoming light sharply, making it responsible for most of the eye’s focusing power. Because it has no blood vessels, it receives oxygen directly from the air and nutrients from the tear fluid.

Sclera

The sclera is the opaque, white, tough outer coat that maintains the shape of the eyeball and gives attachment points to eye muscles. It protects delicate inner tissues from injury and maintains internal pressure.

Introduction

Metabolism generally occurs by orderly, step-wise, sequence that are dependent on the basic laws of thermodynamics. These metabolic pathways consists of a series of progressive, individual chemical reactions.

A Single Step

A single step involves the conversion of a precursor (A) to a given product (B). This reaction is catalysed by a protein molecule, Ea, called an enzyme. An enzymatic reaction is reversible, the forward reaction is described by a rate constant, Kf, whereas the reverse reaction is described by Kr.

Numerous Step

Such a sequence may continue for numerous individual steps, so that the original substrate, A, is converted to the ultimate product, P. This is a typical liner metabolic pathway.

A dichotomous key is a tool used to identify organisms or objects by following a series of choices. The word “dichotomous” means “two parts,” so each step in the key gives two contrasting statements. You choose the statement that matches the organism you are trying to identify, and that choice leads you to the next step. By continuing this process, you eventually reach the name of the organism.

A dichotomous key works like a decision path. At each stage, you compare two features, such as “has wings” or “does not have wings.” These pairs of statements are based on observable characteristics like shape, size, colour, body parts, or behaviour. Because every step has only two options, it becomes easy to sort and identify even very similar organisms.

Scientists commonly use dichotomous keys in biology to identify plants, animals, fungi, or insects. Students also use them in labs, especially in classification topics.…

The skin is the largest organ of the human body, and it is made of three main layers: the epidermis, the dermis, and the hypodermis.

Epidermis

The epidermis is the outermost layer and works like a protective shield. It contains dead cells on the surface and new cells forming at the bottom. This layer also has melanocytes, which produce melanin, the pigment that gives the skin its colour and protects it from sunlight.

dermis

Below the epidermis lies the dermis, a thicker and stronger layer that supports and nourishes the skin. It contains hair follicles, sweat glands, oil glands, nerves, and blood vessels. Because of these structures, the dermis gives the skin strength, elasticity, and the ability to feel sensations like touch, pain, and temperature.

hypodermis