All organisms and plants are made up of millions of cells. The basic structure of a cell is the same in all organisms. It is the smallest unit of life. It comprises of a nucleus and a membrane surrounding the nucleus. Homeostasis is a mechanism that is present in living organisms. It is the course by which plants and animals maintain their internal environment as the external environment changes. In humans, the production of Insulin and Glucagon hormones is a mechanism that looks to ensure that the sugar levels in the organism are under control. Metabolism refers to the chemical reaction within the body that handles the maintenance of energy. Different animal’s burn, fats and carbohydrates to produce energy for their activities. The metabolic rate of an organism is dependent on the activities that the animal performs. Responsiveness refers to the ability of organisms to react to the external changes. For example, during the cold, birds fluff their feathers. The feathers trap air in between them and the layer of air acts as an insulator from the cold. Different animals and plants have means by which they respond to the external environment. By doing this, the plants and animals can protect themselves from harsh conditions. Reproduction is the epitome of life. For this reason, once, mature, animals reproduce and give birth to offsprings that continue their line. Reproduction is one of the most important qualities as no animals can sustain their life forever. When living things, die, they do not fade away into oblivion.