Key points
The differences in characteristics between individuals of the same A group of organisms that can interbreed to have fertile offspring. is called Small changes in living organisms..
Some variation is passed on from parents to offspring, via A small section of DNA that gives a characteristic. during reproduction. This is The passing of characteristics determined by genes from parents to offspring. variation.
Some variation is the result of differences in the surroundings, or what an individual does. This is called environmental variation.
Variation
Humans, dogs and goldfish are examples of species.
Different species have different characteristics from each other. For example, dogs have tails and humans do not. Dogs have fur, but goldfish have scales.
The individual members of a species also have differences in characteristics. For example, humans have different coloured eyes, and dogs have different length tails. This means that no two members of a species are identical.
The differences between the individuals in a species is called variation.
Variation helps a species to survive, by causing individuals of a species to be genetically and physically different.
Video
A guide dog breeder explains the effect of variation on his puppies
Matthew Bottomley: In our puppy block we have in the region of 30 puppies. They're different in terms of their behaviour and temperament, and all of them are unique just like we are as humans.
My name's Matthew Bottomley, I'm head of the breeding programme here at Guide Dogs. And my job involves overseeing the breeding of over 1,300 puppies a year.
Breeding is essential really for producing a really excellent quality guide dog. We need to be able to produce a range of dogs with a range of different temperaments and behaviours, probably physical size, and even colours. So variation, for me, is all those differences. We need those very special traits that are really important for guiding.
So these are both Labrador Retrievers in the same litter, so they're brother and sister but clearly, as you can see, very different as well, just like in the human world we have brothers and sisters that might be described as chalk and cheese, very different from each other.
With the genetics, the way it works is that we all inherit our genes from our mums and dads, as do our dogs, but not always the same genes, and it's those genes that are expressing the coat colour in a slightly different way for these particular two individuals.
Lots of top executives have stress balls on their desk to squeeze when they're feeling particularly stressed, we just come down to the puppy block and have a cuddle with the puppies, what could be better than that?
Genetic and environmental variation
Characteristics in an individual organism are caused by both genetic and environmental variation.
For example, the weight of a dog is caused partly by its genes - inherited - and partly by what it eats - environmental. The height of a sunflower is caused partly by its genes and partly by how much light and water it gets.
| Genetic only | Environmental only | Genetic and environmental |
|---|---|---|
| Eye colour | Tattoos | Height |
| Blood group | Scars | Weight |
| Attached ear lobes | Language spoken | Human's hair colour - can lighten in summer or can be dyed |
| Animal's fur colour | Colour of hydrangea flower - blue in acid soil, pink in alkaline | Size of plant |
Quiz - Genetic or environmental?
Benefits of variation
If all the individuals of a species were genetically identical they would be vulnerable to the same diseases. If this were the case a single disease could wipe out an entire species.
As a result of their genes, some individuals of a species might have better camouflage, or be able to run faster. These individuals are more likely to survive. This is called the survival of the fittest.
The members of a species that survive may reproduce. Their offspring are likely to have the desirable characteristics of their parents. This is how species change in evolution.
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Quiz - Variation
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