Come along on a journey from north to south, using the water as a blue thread to guide you through the Swedish countryside. Along the way you’ll meet many of the plants and animals that live near watercourses in our oblong country.
Every living organism on Earth has a common descent and are thus related. The differences between species have evolved during three and a half billion years through tiny adaptations to each species’ specific habitat. This gradual development is known as evolution. Nature’s super powers haven’t always been so “super”. It has taken both time and a whole lot of trial and error to shape these unique abilities.
Evolution is the long process in which the heritable characteristics of living organisms successively change and adapt, for example by the habitat that the organisms live in.
Examples of evolution by means of natural selection:
The peppered moth
Can you spot the peppered moth? It’s virtually invisible against the tree trunk. Blending into the environment in this way is very good protection against hungry animals higher up in the food chain. In the beginning there were probably peppered moths of all colours. However, those individuals that were easily spotted were soon eaten by birds and small animals.
As time went by, only the brown, well-camouflaged butterflies remained. (That the colourful peppered moths disappeared probably also caused birds to evolve better eyesight, since those birds with the keenest eyes became the best at finding food, and thus survive.) This type of change can take thousands of years.
Evolution is always happening around us, but often so slowly that we can’t perceive the changes. It isn’t until you look back that you discern the differences over time. But if camouflage is so good, why are there colourful animals at all? More on that in the Rainforest.
When Charles Darwin visited the Galápagos Islands, he soon discovered that the Galápagos finches differed depending on which island they lived on. The finches were of the same species but some of them had long beaks, others had short ones. The birds were also of different sizes. Darwin concluded that these genetic differences depended on the varying biological conditions on the islands, and that the birds had evolved over time to suit their specific habitats.