What biological explanation that allow plants like the Venus flytrap to digest insects?
In: Biology
If you’re asking how they do it, they secrete a bunch of enzymes that effectively disassemble the insect on a molecular level, and afterwards absorb the resulting insect-soup. If you’re asking why they do it, it’s to acquire various nutrients that they would usually get from the soil, but can’t for whatever reason. This is most often nitrogen in nitrogen-poor soils, but IIRC, there are some carnivorous plants that digest things for other nutrients, not just nitrogen.
Note that this is different from the carnivorous nature of various animals; carnivorous plants are still autotrophs, they still make their own energy through photosynthesis just like other plants do. They only ‘eat’ to get components for themselves that they don’t have easy access to, not to gain energy from their food.
These plants tend to occur in areas where certain nutrients such as Nitrogen are absent or in critically low concentrations in the soil. The plants fill a niche by sourcing those nutrients from animals like insects or small amphibians instead.
If you are looking for a ‘how did this behavior evolve’, you are going to run into a few issues.
One is that historical ‘records’ of plants can be harder than animal fossil records for tracing evolution.
Another is that you are going to get a lot of ‘speculative’ answers that wave their hands and say “this might be a mechanism for it?”
The evolutionary advantage is somewhat clear, for example insects have nutrients so plants that can trap and digest insects will be able to survive with worse soil conditions, outcompeting plants without that trait. In some sense that is a good ‘why’ answer.
As for ‘how’, it is a cool area we are still looking at. https://www.science.org/content/article/how-venus-flytraps-evolved-their-taste-meat
You can think of a few evolutionary steps that might be involved, but it will be conjecture. AKA
– a plant species has many crawling insects die either on it or in the soil under it. Ones which have a mutation that makes their leaves act more like roots and try to ‘digest’ nutrients on their surface such as nitrogen does much better.
– A plant which has a mutation to produce a substance that harms insects prevents pests to some degree.
– If you have both, a faster and faster way to break down insects might be advantageous so you don’t lose the nutrients to rain or other insects.
– A plant which can move its leaves quickly is able to repel insects based on movement or rotate to face the sun more efficiently.
– trap designs might be efficient in attracting insects for pollen or reproductive reasons (such as insects collecting and spreading pollen when funnelled to it). But a design which then traps the insects might accidently be even better for survival when there are multiple ways of reproducing and it already has a weird way of ‘digesting’ insects.
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