Examples Of Natural Selection At Work

We can see evolution at work in examples of natural selection, where the environment determines which animals will survive and breed.

How Does It Work?

The basis of natural selection is variation. We see this all around us. We do not look exactly like our parents, no two dogs are exactly identical even if they are twins, and all trees of a particular species will grow in its own shape, never identical to another.

It is these tiny differences between individuals that allows such great changes like those in the fossil record to take place over long periods of time. Examples of natural selection can be found on any scale.

Evolution Is Not A Choice

Living things do not choose to become larger, faster, better camouflaged and so on. There is no goal of improvement in the mind of an animal - it is merely doing its best to survive in the present moment.

Each female animal mates and produces a litter of offspring that all look very much like her but not exactly the same. Because of the slight differences in the offspring of one litter, some will do slightly better than others in gathering food, defending territory or whatever it is that makes for success with that species at that time.

Sometimes the difference won't be enough to affect the individuals' chances of mating, but sometimes it will. It is usually when the going gets tough that these differences force changes in the species.

An Example: The Coats Of Puppies

Take for an example the idea of a litter of ten puppies born in bad times; there is very little food to go around. A couple of the ten have black coats, while the rest have mixed colours of coats ranging from white, to patches of brown and so on. Because there is not much food around (maybe a decade long drought is still continuing) prey animals are very nervous and are extra alert to being attacked. The dark coats of the two black puppies allow them to get just a little bit closer to their victims before they pounce. This increases the amount of food they can get while reducing the energy they need to spend on getting it.

This could mean the difference between life and death for the puppies. Clearly those two black coated puppies are more likely to grow and have offspring of their own than the other puppies. While their offspring will also have a range of coat colours, there is a higher chance that there will be more black coated puppies in the next generation. If this situation continued year after year, pretty soon there would be plenty of black coated dogs running around and very few with other coloured coats.

The same idea can be applied to examples of natural selection regarding size, speed and even diet. Slow change from one generation to the next gives gradual yet definite change in a species.

Extinction

Sometimes the small changes that happen each time offspring are produced don't give any real advantage to the offspring, or actually make things worse for them. Or maybe they make things better, but not good enough to survive. When all the members of a population die, it is extinct. When all the populations of a species die off, the species is extinct.

In evolution, you don't have to fail to become extinct. You just have to succeed a little less often than your competition.

While extinction can be rapid and dramatic, as in the case of the dinosaurs, it can also be slow and drawn out, with almost no noticable difference in populations from one generation to the next until the animal is just not found any more.

Evolution Is Unpredictable

There are no guarantees with natural selection. Those animals in the greatest abundance, that are the most adaptable and seem to be able to cope with all difficulties are no more guaranteed a spot in the future of things than a species that is struggling to survive. This sounds weird, but time and again the fossil record shows us that species that look like real winners disappear without trace. This was the case for Marella in the Burgess shale, the most numerous and widespread of all organisms at the time. Yet it became extinct without a single living descendant.

Consider also the dinosaurs. They had filled almost all land niches, and their reptile cousins filled the skies and seas. Yet they all died out with only the birds remaining.

Even superior intelligence is no guarantee; those other humans, the Neanderthals, also became extinct. Even their strength and quick wits did not give them a promise of survival.

There are many examples of natural selection such as these at all levels, from major groups of animals to families, to individual species.

Luck Is Also Important

Being super camouflaged and having ultra sharp eyesight doesn't help you reproduce if you're caught in a tsunami and killed. Luck is also a factor in survival. Luck is blind and throws in randomness. This is why evolution is not a steady march towards ever more complex and perfect creatures, and why those that appear weak or less well adapted sometimes survive and thrive.

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