Why Do Meat-Eating Plants Trap Insects?
There are more than 600 known species of carnivorous plants spread out across the entire world. They are uniquely known for their ability to trap insects and digest them. Even more impressively, they accomplish this without a complex nervous or digestive system. The reason why they do this lies in their evolutionary roots.
Other People Are Reading
-
Evolution
-
Carnivorous plants have evolved in environments that offer low-nutrient soil such as bogs and rocky outcroppings. Despite the paucity of carnivorous plants in the fossil record---their soft parts just don't fossilize very well---it is believed that they first began to passively absorb the nutrients from decayed insects before evolving complex traps to lure them.
Nutrients
-
Most plants have evolved to siphon their nutrients through roots in the soil. However, the low-nutrient soil where carnivorous plants grow lacks certain elements such as nitrogen and phosphorous. In order to compensate, carnivorous plants have shifted their absorption of nutrients from osmosis through roots to a crude form of digestion.
-
Insects
-
Carnivorous plants rely on a steady supply of insects for food. Flies in particular are an easy source of prey. These nitrogen-rich insects are necessary for protein synthesis within the plant. In addition, the digestion of insects also helps supply phosphate for nucleic acid synthesis and iron for chlorophyll synthesis.
Cost
-
According to Aaron Ellison and Jim Karagatzides of Harvard University, research has revealed that the cost of the trapping and digestion mechanisms are cheaper than the cost of a normal leaf, so carnivorous plants are expending less energy---though this is somewhat mitigated by the fact that their roots are much weaker and they produce energy via photosynthesis at a much slower rate. However, a single insect can usually keep a carnivorous plant fed for a few weeks.
Significance
-
The cost-effectiveness of carnivorous plants is not immediately self-evident, but the trigger and digestive mechanisms are much less involved than in their animal counterparts. The evolution of the nervous system in animals first required a basic response system, then a complex network of nerves and finally the evolution of the brain. But the trigger mechanism in carnivorous plants was likely a quick (in geological time) response to the low-nutrient soil. In fact, carnivorous plants likely evolved several different times from a common ancestor predisposed to a carnivorous lifestyle.
-
References
- Photo Credit orchidée image by Ludovic LAN from Fotolia.com
