Tag Archives: natural selection

Ask the Scientist: Morgan’s Question

I have always found that young people ask the most insightful of questions. They can come up with questions we would never had thought to ask, and yet, once posed, make us sit up and think “actually, yeah, why is that?”

(L-R) Morgan, Lara and Brooke

(L-R) Morgan, Lara and Brooke

Following my recent interview with the Lab_13 children of Irchester Community Primary School I was lucky enough to receive three such questions from three very bright and talented young ladies. Together with my colleagues Dr James Sleigh and Dr Stuart Grice, we have prepared responses to each of their questions in turn.

To make them a little easier to digest, I will post one a week. Our first question comes from Morgan, age 11. We hope you enjoy reading them, and feel free to add your own thoughts below!  

I know we all have different DNA but why? Why do we need to be different?

– Morgan, aged 11

Everybody does indeed have different DNA, and that is one of the things that makes you unique and who you are. However, the sequence of your DNA is almost 99.9% similar to that of another person. That means that if you were to look at the letters that make up your DNA and my DNA, 999 out of 1000 are likely to be the same. This percentage gets even higher when you compare your DNA with a relative.

If you go in the opposite direction and compare yourself with a chimpanzee, the differences become bigger and that similarity percentage goes down. I’m sure you’ve all heard of people tracing their family histories and drawing a family tree.tree of life zazzle 2 Well imagine doing that and going back a few million years. Eventually, you would come across an ancestor that you share with a chimp!

Now keep on going. If you were to go back billions of years until your tree includes every animal that ever lived, you would have drawn the “Tree of Life” and you would be able to see how life on earth has evolved, and how new species came to exist.

And this is why we all have different DNA and need to be different. For a species to be able to survive and thrive, it needs to be well adapted to its environment. Think of an African elephant with its large ears to improve heat loss and a polar bear with its extremely thick fur to keep it warm. Each species has many ‘adaptations’ in order to survive. If you were to swap the two and put an elephant in the Arctic or a polar bear in Africa, neither would live for very long!

Perfectly adapted to their environment

Perfectly adapted to their environment, but not so good in each others!

These adaptations have come about because of evolution by natural selection acting on their DNA.

playdna dna genes chromosomesIt is actually the genes in DNA that result in the different characteristics we see in all species. A gene is simply a short section of DNA that tells our cells what to do. If you think of your DNA as a recipe book, the genes are the individual recipes. Each of us has the same set of genes – about 20,000 in all. The differences between people come from slight variations in these genes.

Differences in our genes, which can come about through natural mutations in our DNA, lead to new characteristics. A lot of these changes may be bad, but some may be good, and improve the chances of an animal surviving. Those animals with genes that improve their chances of survival will be more likely to live long enough to pass on their DNA to their children than those animals that don’t possess the advantageous genes.

In recent years our environment is improving again, and with lower levels of pollution we are starting to see an upturn in lighter-coloured moth numbers- what colour are the moths near you?

In recent years our environment is improving again, and with lower levels of pollution we are starting to see an upturn in lighter-coloured moth numbers
– what colour are the moths near you?

When this selection of genes occurs over long periods of time, animals within a species can become more different from each other until two groups form that can no longer have children together. When this happens, new species have formed.

The differences in human DNA allowed our species to adapt to the environment over generations. If we go back a few thousand years, when there were no computers, or telephones, and we were living in small huts and caves, life was much harder and there was much more danger in the world. If we all had the exact same DNA, we would all be very similar in our appearance and our physical and mental abilities. That means that we would have been much more likely to die out as a species if a life-threatening change in our environment occurred, perhaps a new disease that no one was immune to for example.

Monocultures are genetically identical plant species: what do you think will happen to this crop if it was attacked by disease?

Monocultures are plantations of genetically identical plant species: what do you think will happen to this crop if it was attacked by disease?

However, having small differences in our DNA means there is a chance that some people could be immune to that disease. If attacked by a large predator like a lion, it would be those who could run faster that would survive, or maybe those who were smarter and able to hide better. These individuals would be more likely to stay alive long enough to pass on their advantageous genes.

Being different then is a good thing, not only because it means that life is a little more exciting with the diverse range of people you get to meet, but also because we are more likely to survive into the future as a species!

1 Comment

Filed under Genetics, Science, STEM