Variation
Individuals in a population are usually similar to each other, but not identical. Some of the Difference between individuals, distance from the norm. within a A type of organism that is the basic unit of classification. Individuals of different species are not able to interbreed successfully. is To do with inheritance because of genes., some variation is Differences between individuals of a species due to factors in their surroundings., and some is a combination of both.
Genetic causes of variation
Children generally look a little like their mother and their father, but are not identical to either. They inherit their features from each parent's DNA. Every sperm and egg cell usually contains half of the genetic information needed for an individual. This means sperm and eggs usually contain half the number The structure made of DNA that codes for all the characteristics of an organism.. When the chromosomes fuse during The joining of a male and female gamete., a new cell is formed, which is known as a A fertilised egg cell.. It has all the genetic information needed for an individual.
Examples of genetic variation in humans include blood group, eye colour and whether you have lobed or lobeless ears.
Environmental causes of variation
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 little or too much your body shape may change. If you eat too much you will become heavier. A plant in the shade of a big tree will grow taller to reach more light.
Other examples of features that show environmental variation include:
- scars and tattoos
- language and accent
- flower colour in hydrangeas as these plants produce blue flowers in Having a pH lower than 7. soil and pink flowers in Having a pH greater than 7. soil
Genetic and environmental causes together
Phenylketonuria (PKU) is an example of how the genes and the environment may work together. The disease is caused by a build up of phenylalanine in the bodies of people who have a variant of the PAH gene which codes for an enzyme which does not work properly. The disease is managed by excluding phenylalanine from the diet.
Height is an example of when genetic and environmental causes can combine. Tall parents will pass genes on to their children for height. Their children have the genetic potential to also be tall. However, if their diet is poor then they might not grow as tall. So their environment also has an impact on their height.
Learn more about variation with Dr Alex Lathbridge.
Listen to the full series on BBC Sounds.
In this podcast, learn the key facts about variation. Listen to the full series on BBC Sounds.