Variation
Individuals in a All of the members of a single species that live within a geographical area. are usually similar to each other, but not identical. Some of this 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 is environmental - the conditions in which they have developed and some is a combination of both.
The The alleles that an organism has for a particular characteristic, usually written as letters. is the collection of Different forms of the same gene. that determine characteristics and can be expressed as a The visible characteristics of an organism which occur as a result of its genes.. Most phenotypic features are the result of multiple genes rather than single gene inheritance.
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 contains half of the genetic information needed for an individual. Each sex cell is described as A sex cell (gamete) that contains one set of chromosomes., and has half the normal number of 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, and is described as A cell that contains two sets of chromosomes.. It has the full number of chromosomes.
Examples of genetic variation in humans include:
- blood group
- skin colour
- natural eye colour
Whether you have lobed or lobeless ears is due to genetic causes.
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 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.
Other examples of features that show environmental variation include:
- scars
- 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
Some features vary because of a combination of genetic and environmental causes. For example, tall parents will pass genes to their children for height. Their children have the genetic potential to also be tall. However, if their diet is poor then they will not grow very well - their environment also has an effect on their height.
