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Why Insects are so successful?
Insects comprise about 95% of all known animal species. Actually it is insects instead of human (nor mammal) who dominate this planet. Why Insects can be so success? The answers can be very complicated and there are a lot of factors. However, we can see two obvious factors which contributed to the success of insects.
Flying Wings
Insects are the first group animals known to fly on earth. They are the first one who invented the flying wings. There are only four groups of animals on earth have wings can fly. They are insects, pterosaurs, birds and bats. Except for the pterosaurs they extinct together with dinosaurs. All the others can be considered as the success group of animals on earth, although all of them still cannot compare with insects. Birds descended from dinosaur and become an ‘Birds Class’ in animal kingdom. You may think that bats are not quite success, this is only because we know not much about bats. The number of bat species is the largest in mammal.
By the invention of the flying wings, insects suddenly extended their living habitat - from land to air. Because they are the first one in this habitat, there are a lot of space and resources for them to explore. The room for evolution is suddenly increased and the numbers of insect species can also be increase as explosion.
When there is the available habitat, there will be the explosion of number of species. Mammal species increase after the extinction of dinosaurs is a good example. Mammals existed long before the dinosaurs were extinct. At that time mammals were living something like the rat’s living today. Most the habitat was occupied by the dinosaurs and other reptiles, not much can be explore for the mammals. For some reasons, the dinosaurs became extinct in a short period and suddenly there was the empty habitat. Mammal completed with other animals at a better position, and eventually replace the dinosaurs. In the evolution history there is a lot of species number explosion due to the sudden appear of habitat. The habitat appear could be due to external factors, like the cause of dinosaurs extinction, or due to the species themselves, like the adoption to some once hazard environment (e.g. breath oxygen) , the invention of organ (e.g. flying wings, eyes) , and the change of life form (e.g. single cell to multi cell, from water to land).
Flowering Season
The second reason for the success of insects is the co-evolution of insects with plants. By the help of insects, plants invented their important organ - flower. The insects not only consume the plants but co-evolutes with them and help plants to develop. One example is the beetles and the flowers. When flowers first appeared on earth, it was also beetles first appear on earth. Beetles were not necessary depend on flowers for food, however, flowers provides food for beetles and let them to help for pollination. Flowers and beetles both benefited form each other. Beetle species become the largest number order in Insects. The butterflies and bees that depend on flowers appear after the booming of beetles, which is another story.
I gauss the evolution of flowers was more or less like this. Many millions years ago, just before the flowers existed on earth, plants were all green in colour. Plants had already developed two sexes for the propagations of their offspring. They had developed a special organ for genetic information exchange - pollination. The plants, basically were not able move, pollination was done only by the help of the wind. The wind carry the pollens from plants male sex organ to fertilize the female sex organ. This is not very efficiency because the wind will carry the pollens to anywhere. Then here come the winged insects. Those insects, such as beetles, came to eat the pollens. The insects visited many similar type of plants for the food. By doing this, the insects help to carry the pollens from one plant to the others, i.e., a more efficiency pollination. Both party benefited and became depend on each others. The plants sexual organs become more colourful to advertise to the insects, some plant develop special fragrance to attach the insects. Instead of supplying the pollens as food, some plants supply the liquid with sugar. This plants sex organ became the flowers we see today. For the insects, they become more rely on the flowers as the food source. Some insects become hairy so that they are more efficiency to carry the pollens.
Why beetles are so success?
Beetles may be success in number of species, but not quite when counting the
number of individual. When we go out to the field, usually you will see a lot of
ants, moths, flies, and grasshoppers. If you visit some special place, such as
pond, rivers, flower plants, forest, etc, you may easily found the dragonflies,
butterflies etc. But to find a beetle may not so easily. Instead of saying
beetle is a success family, I will say they have the most number of species in
their order. So the correction question should be: Why there are so many species
of beetles?
I think of the following reasons;- 1. The ways that we classified all different species of beetles as one order may be not fair. When comparing beetles with other orders of insects, I think we put two many different families into one Coleoptera Order. We put every insects with hard forewings into Coleoptera Order. If we put grasshoppers, stick insects, mantids and cockroaches in different orders, why do we put ladybird beetles, scarab, longihorn, weevil in one order?
2. Beetles evolved in flowering season. By the help of insects, plants invented their important organ - flower. The insects not only consume the plants but co-evolutes with them and help plants to develop. When flowers first appeared on earth, it was also beetles first appear on earth. Beetles were not necessary depend on flowers for food, however, flowers provides food for beetles and let them to help for pollination. Flowers and beetles both benefited form each other. Beetle species become the largest number order in Insects.- 3. Beetle specialized in food and live in isolated environment. After long time of separations, different group of beetles become different species.
4. Beetles are among the first group of insect who gain the benefit of complete metamorphosis, i.e., they develop from eggs, larva, pupa to adult. They have two completely different body shape and there are a lot of advantages. Those include adults and larvae not necessary to complete for the same food and living resources, adapt to different conditions due to seasonal changes, and to avoid predators in different stage.
