Complex organisms are made up of specialized cells to carry out each of the specialist functions taking place in the organisms body. Each group of specialized cells is different in shape, size and chemical composition to make it efficient for its dedicated task in the body. For example red blood cells are biconcave in shape which allows them to rapidly absorb oxygen from the lungs. They also contain hemoglobin which stores the absorbed oxygen and transports it to other parts of the body. Red blood cells are the only cells in the body with these properties which are best suited to help them fulfill their specific role in the body.

A human body needs to respire, eat and digest food, excrete toxic wastes from the body and need to have a healthy immune system to save the body against diseases in order to stay alive.

Red blood cells are biconcave in shape which allows them to rapidly absorb oxygen from the lungs and easily pass through blood vessels. They also contain hemoglobin which stores the absorbed oxygen and transports it to other parts of the body.

Any extra glucose in the body is stored in an organisms body as fat. The fat cells are equipped with large vacuoles to help them fulfill their role as storage places in the organism’s body.

The DNA strands contain information about each and every property of the organism. Therefore, even though every living being starts its life from a single cell, the information coded in the DNA of this single cell, enables the organism to develop all other required specialized cells as it develops in the embryo of its parent.

Yes plant cells also specialize in the same way as animal cells according to their needs. For example a plant does not need red blood cells to transport oxygen to its various parts and therefore red blood cells are absent in plants but the primary purpose of existence of plants is to manufacture food (for itself and all other organisms on earth) and therefore plant cells specialized for this role contain chloroplast in them to store sun’s energy in them in order to photosynthesize.

Single celled organisms do not need to show specializations because they in fact are composed of one cell which is versatile enough to sustain its life. In such organisms, specialized activities are carried out by different parts of the cell, for example the mitochondria powers up the cell by respiring and breaking down food to create energy.