Look at these baby animals. You will have immediately observed how cute and fluffy they are but you will
also have noticed that they are different - they vary. Yes - some are puppies and some are kittens.
There is a great deal of variation between species but also there is variation within a species. One
puppy is fluffier than the other, they have different colour fur and the kittens have different coloured eyes.
Variation is the differences in the characteristics of individuals in a population. It can be due to genetics,
the environment or a combination of both.
Let’s start with genetics. Different members of a population have different DNA, unless they are identical
twins. This means they have different versions of genes, called alleles, and these alleles give rise to
For example, on the eye colour gene this kitten has an allele for blue eye colour whereas this kitten has
an allele for brown eye colour.
If the species reproduces by sexual reproduction, the random mixing of alleles from both parents results
in extensive genetic variation within a population of a species. This means that some individuals are
better adapted to their environment than others, allowing natural selection to take place. For example, in
a population of rats, some will have better eyesight than others. These will be able to avoid being eaten
by predators so are more likely to survive to reproduce and pass on this advantage to their offspring. If
you want to learn more about natural selection, watch this video.
Some examples of variation in humans that are controlled only by genes include eye colour and blood
group. If you have blood group A it is because you have the alleles for this characteristic. This is genetic
variation, and it is something that you were born with, and nothing can change it.
Some variation is due to the environment, or lifestyle of the organisms. Examples in humans are hair
length (it depends on how short you decide to cut it), your accent, as this is linked to where you live and
if you have any piercings, tattoos or scars. These are characteristics that you acquire throughout your
Many characteristics are due to a combination of both genetics and the environment. For example, the
height a person can grow to is determined by genetics - tall parents tend to produce tall children.
However, a person will not grow to their potential height unless they eat a healthy, balanced diet. Also,
there is some debate on how much intelligence is due to genetics or the quality of education a person
receives - is intelligence more due to nature or nurture?
To answer these questions scientists can do experiments using identical twins. If the characteristic in
both twins is the same then it is most likely due to genetics. If it is different, then the environment has
played an important role. For example, identical twins will have the same eye colour as this is only due to
genetics but they will have different personalities, talents, likes and dislikes and this shows that these are
also influenced by the environment.
So, in this video we learnt about variation, and how it can be controlled by genetics, the environment or
Animation & Design: Waldi Apollis
Narration: Dale Bennett
Script: Lucy Billings
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