Variation is the difference between individuals, distance from the norm.
The causes of variation can come from sexual reproduction. For example, children usually look a little like both their mother and their father, but they will not be identical to either one of them. This is because they get half of their inherited features from each parent.
Characteristics of animal and plant species can be affected by factors such as climate, diet, accidents, culture, and lifestyle. For example, if you eat too much you will become heavier, and if you eat too little you will become lighter. A plant in the shade of a big tree will grow taller to reach more light.