Insects are the most successful animal group. What factors have contributed to their success?
Insects are the most successful animal group. They are extremely diverse and abundant. They are present in the sea, in freshwater, on land and in the air. They occupy every ecological niche. Arthropods are not only extremely diverse but are also numerous as individuals. There are approximately 200 million insects for every human being on the Earth.(1) They have a huge impact on humans and our activities. They are pests of both food and animals, and are responsible for disease transmission. They also create important food sources and are beneficial through processes such as pollination and scavenging.
The high degree of insect diversity is due to a combination of high rates of speciation and low rates of extinction.(2) The orders with the highest species richness include Coleoptera (beetles), Hymenoptera (ants, wasps and bees), Lepidoptera (butterflies and moths), Diptera (true flies) and Hemiptera (bugs). (2) Many factors contribute to the success of the insecta such as their small size, their protective cuticle, an efficient nervous system (the blood-brain barrier and sensory neuromotor refinement), the evolution of flight and a high reproductive rate.
The size of an organism determines how the environment will affect it. Most insecta are small; the average is around 3mm in length. The physical environment tends to favour these sized animals. For example;
“You can drop a mouse down a thousand-foot mine shaft and, on arriving at the bottom, it gets a slight shock and walks away. A rat is killed, a man is broken and a horse splashes.” (J.B.S. Haldane)
This is due to the ratio of surface area to volume; the bigger they are, the harder they fall. Also, small animals are relatively more powerful than large ones. The cross-sectional area of insect muscle is large relative to their mass. For example; an ant can carry a load many times heavier than its own body weight. Their size has also allowed insects to evolve to occupy many more ecological niches than larger
The high degree of insect diversity is due to a combination of high rates of speciation and low rates of extinction.(2) The orders with the highest species richness include Coleoptera (beetles), Hymenoptera (ants, wasps and bees), Lepidoptera (butterflies and moths), Diptera (true flies) and Hemiptera (bugs). (2) Many factors contribute to the success of the insecta such as their small size, their protective cuticle, an efficient nervous system (the blood-brain barrier and sensory neuromotor refinement), the evolution of flight and a high reproductive rate.
The size of an organism determines how the environment will affect it. Most insecta are small; the average is around 3mm in length. The physical environment tends to favour these sized animals. For example;
“You can drop a mouse down a thousand-foot mine shaft and, on arriving at the bottom, it gets a slight shock and walks away. A rat is killed, a man is broken and a horse splashes.” (J.B.S. Haldane)
This is due to the ratio of surface area to volume; the bigger they are, the harder they fall. Also, small animals are relatively more powerful than large ones. The cross-sectional area of insect muscle is large relative to their mass. For example; an ant can carry a load many times heavier than its own body weight. Their size has also allowed insects to evolve to occupy many more ecological niches than larger