Mutations and evolution

A meadow. Full of life. All life consists of cells. This daisy too. Here is one of the cells of the daisy, with the genome, DNA, in the cell nucleus.

Now it divides, and during the cell division, DNA is copied. The new cell gets a copy of the first cell's - the mother cell's - DNA. A copy which is perfect. Or almost perfect. Changes in the genome, mutations, occur all the time.

The new cell then gets DNA molecules that are a tiny bit different from those of the mother cell. But in the vast majority of cases it has no significance at all. But there is a special case. Something very rare, that has had an enormous significance. Watch.

We see one of the daisy's cells again. It divides, and during this division, two important things happen. There is a mutation... ... in a gene, that is in any of the parts of the DNA which are recipes for proteins... And it happens in a sex cell...

And a sex cell can be the start of a totally new individual. So, if this cell is conceived and sets root, and then grows to become a new flower... ... then all the other cells in that flower get copies of the changed gene. The new daisy has slightly different genes, and slightly different properties than the previous generation. And slightly different properties than all the other daisies in the meadow.

Now the question is, which one of these individuals holds up best in the environment? Which can best endure dry weather? Which can best handle heavy pelting rain? The daisies with the best characteristics in this particular environment will survive, and spread exactly those characteristics. We see a natural selection.

These types of mutation, the ones that change the offspring, they almost always cause the offspring to hold up worse. Then the natural selection causes the mutation to disappear. The individual with the new, impaired trait will have a lower chance of survival. The trait dies out. But if the rare thing happens, that the mutations cause an improvement, that is a better adaptation to the environment, the mutation - and the trait - remains.

And is spread. Then the altered, mutated, daisy will live on. It reproduces, generation after generation. And every generation has the mutated gene with the new trait. At some point, another new mutation may occur...

in a gene, in a sex cell, that will become a new individual, and if this tiny change also fits well into the environment, the flower will change one step further. It will be just a bit more different from the first daisy. What we have seen are two small steps in the process that has caused the development of all life on earth, evolution. The DNA molecule is copied, but it is copied only almost perfectly. This is the foundation of evolution.

During the development of life, traits and characteristics have occurred through random mutations in the genome. This has caused changes in traits, in tiny, tiny steps from one generation to the next. Natural selection decides which traits will become successful and spread. Although each step is tiny, and every mutation might seem insignificant, all those steps have been taken over the course of hundreds of millions of years, and they have driven the development of life, from single celled organisms to the variety of species that we see today.