How do trees know?
How does a tree (or any plant, really), know to evolve to produce a delicious fruit or a poison berry, a seed inside an impenetrable shell, or invent a type of flying machine, in order to reproduce? (Each of these examples exists in my backyard) How do they receive feedback about their evolutionary experiments? How do they know it worked/failed. [10]
If, over a long time period, that tree’s particular characteristics lead to the species surviving, then it worked.
If it doesn’t, then the species dies out.
There’s no feedback, other than whether or not the species continues to exist.
as, for example an elm or maple? a random mutation may have provided a small spur to a seed. the spur changed the trajectory of the falling seed and may have allowed it to fall further from the parent plant and into a more ideal growing environment for simply further afield, which would allow it to slightly out-complete others.
if this change proved sucessful over time, then the mutation would likely get more pronounced as long as it continued to improve the plants fitness for its environment. 100,000 years later you have seeds with glide wings.
Makes sense. I realize the first part of the Q was simplistic. And I should have known (I did) the answer. It’s the design I’m most perplexed by - not the why, the how. I guess this would be the simplest way to explain it.
Still, that birds, insects, and trees, all have wings… It’ll never not be mind blowing.
How does a tree evolve a wing? - not to fly, but to propagate.
Parallel evolution makes sense to me in the animal kingdom, but a tree evolving winged vehicles for their seed is just mind blowing when I think about it.
if you want a contemporary and highly entertaining way of exploring evolution, check out baba brinkman’s rap guide to evolution
https://www.youtube.com/channel/UCz9Qm66ewnY0LAlZlL4HK9g
its readily available on the net and its an excellent and fun way to contemplate many of the questions you have.
if a tree can start to flower and drop seeds around year 3
Did you just make this up, or is it actually true for these kinds of trees that can be several thousand years old?
It doesn’t matter how old the trees can ultimately live
It has given me the hint to ask this question :)
I’m not arguing, I wanted to learn something.
Number was plucked out of my ass. But sure, let’s look at a redwood and see when they start reproducing.
The Sierra Redwood can reproduce sexually (seeds in cones) as early as 24 years old, but one source I found said that seeds are usually not high-quality until the tree is 200+ years old. It also takes about a 2-year maturation period within the cone before being ready for planting. Other types of redwoods can reproduce asexually, which may have an effect on the rate of expression of the mutated genes.
Sierra Redwood can reproduce sexually (seeds in cones) as early as 24 years old, but one source I found said that seeds are usually not high-quality until the tree is 200+ years old.
That’s quite interesting. And impressive, too!
Thank you for looking it up.
You might be underestimating the timescales involved.
For example, grass - super simple organism, right? Should have appeared early on? No, dinosaurs appeared before grass did. But when the first grasses did evolve, wow, they were successful on a scale that is hard to overstate.
The beauty of sexual reproduction, from an evolutionary point of view, is that by its very nature, it allows many experiments to take place at once. The success criteria of each experiment is how many babies can the subject make.
Little wings evolve on seed pods for the same reason they evolved on anything else. For whatever reason, each step along the way made them a tiny bit more successful at having babies than those without.
Maybe a little spike makes them slightly less likely to be eaten, a bigger spike less likely still. A flatter spike helped them catch the wind and scatter further afield, and broader ones further still.
There’s no feedback needed for individuals in this system - it’s literally a numbers game based on who/what can make the most babies. They’re the ones who, millions of years down the line, end up winning.
berries and wings don’t just randomly appear out of nowhere from year to year do they?
They do! Any useful trait is likely to appear more than once in different species.
Your senses do not feed back into evolution. It’s all random mutations that happen to make it slightly better at serving.
For many things that seem to require a large single leap in progress it turns out that there is a clear story of gradually developing it over a long time.
Plants with more flexible and responsive genetic systems were better able to adapt to changing environments and thus more likely to survive and reproduce, so yeah. However, the basic building blocks of these systems - DNA replication, gene expression, and the fundamental biological processes arose from simpler chemical and physical interactions that were likely governed by principles of self-assembly and thermodynamics. The primary drivers are different at different levels of abstraction and complexity, and there’s dynamic interaction across levels.
Thermodynamics -> Natural Selection -> Responsive Genetics -> Memetics -> Metamemetics (probably?)
We “boil things down” to Natural Selection or Thermodynamics as is convenient for communication, but the higher levels affect the lower as well. So we can’t really reduce them like that without losing important information.
How do they receive feedback about their evolutionary experiments? How do they know it worked/failed.
They’re not performing experiments, mutations are random and they either help the plant survive/reproduce, make it harder to do so, or have no appreciable effect. If it helps the plant, more of them will survive and reproduce, meaning more of the plant with that mutation will be more common. If it hurts, then it will be less common.
Let’s dive a little deeper. Cause the molecular basis of evolutionary innovation in plants is complex, with genetic and epigenetic factors. Whole genome duplications (WGD) have occurred multiple times in many plant lineages, providing raw material for evolutionary innovation. These events can lead to sub-functionalization and neo-functionalization of duplicated genes, allowing for the emergence of novel traits. Transposable elements (TEs), once dismissed as “junk DNA,” are now recognized as major drivers of plant genome evolution. They can introduce regulatory variations, alter gene expression patterns, and even create entirely new genes. It’s less common in plants than in prokaryotes, but horizontal gene transfer (HGT) (particularly involving mitochondrial genes) do introduce novel genetic material for evolution to act upon.
The field of evolutionary developmental biology (evo-devo) has revealed how changes in developmental pathways can lead to major evolutionary innovations in plants. MADS-box genes, a family of transcription factors, play crucial roles in flower development. Modifications in MADS-box gene networks have been implicated in the evolution of diverse floral morphologies and fruit types. Similarly, alterations in phytohormone signaling pathways can lead to significant phenotypic changes, affecting everything from growth habits to fruit development.
When examining the molecular evolution of specific traits, we find fascinating examples of genetic repurposing and innovation. The evolution of fleshy fruits involves complex genetic networks. For instance, the FRUITFULL (FUL) MADS-box gene, originally involved in Arabidopsis silique development, has been co-opted in tomato to regulate fruit ripening. This exemplifies how existing genetic modules can be repurposed for new functions. The evolution of plant defense compounds involves gene duplication and neofunctionalization of enzymes in various biosynthetic pathways. For example, the diversification of glucosinolates in Brassicaceae involved duplication and subfunctionalization of cytochrome P450 genes. The evolution of seed dispersal structures often involves modifications of existing developmental programs. The wing-like samaras of maples, for instance, likely evolved through alterations in carpel development pathways.
While plants don’t receive conscious feedback, several mechanisms can influence the trajectory of their evolution. Some plants can pass on epigenetic modifications, such as DNA methylation patterns, in response to environmental stresses, potentially priming offspring for similar conditions. Through niche construction, plants actively modify their environment, which can create feedback loops affecting their own evolution. For example, changes in soil chemistry induced by plant exudates can influence selection pressures on subsequent generations. Plant-pollinator and plant-herbivore interactions create complex fitness landscapes that drive reciprocal evolutionary changes. These can be modeled using adaptive dynamics or evolutionary game theory approaches.
It’s crucial to recognize that evolution doesn’t always produce optimal solutions. Constraints such as pleiotropy, where one gene affects multiple traits, and developmental or physiological limitations can restrict evolutionary trajectories. This more nuanced view acknowledges the intricate molecular and genetic underpinnings of plant evolution, moving beyond the simplified narrative of random mutation and selection.
Modern research in plant evolutionary biology employs various cutting-edge techniques. These include genome-wide association studies (GWAS) to identify genetic loci associated with adaptive traits, transcriptomics and proteomics to understand gene regulatory networks underlying trait evolution, CRISPR-Cas9 gene editing to test the functional significance of specific genetic changes, and phylogenomics to reconstruct evolutionary histories and identify instances of convergent evolution.
What I’m saying is, evolution as a complex process involving multiple levels of biological organization, from genes to ecosystems. It’s a sophisticated mechanism underlying the diverse adaptations we observe in plants, and a deeper understanding of how traits like delicious fruits, toxic berries, protective seed coats, and innovative dispersal mechanisms have emerged over evolutionary time is a worthwhile pursuit.
It’s not that complex.
A mutation happens. It can result in either a disadvantage that prevents the plant from surviving to reproduce or an advantage that helps the plant survive to reproduce.
There’s no “knowing” involved. There is no intent on the part of the plant. It’s just random. You’re seeing the descendants of the plants that got an advantageous mutation.
What you’re not seeing in your yard are the billions of different plants that never survived because their mutation was a disadvantage.
In addition to what other people said, I’ll focus on the delicious fruits.
A lot of wild fruits are awful when raw. Crab apples are a good example - small, tough, excessively tart. But then you get humans picking the least awful of those fruits, and spreading their seeds (sometimes without a thought, sometimes on purpose), you’re effectively selecting the best-tasting ones. And across multiple generations, the fruit goes from barely edible to passable to okay-ish to good-tasting.
In other words, plenty tasty fruits out there are not the result of trees “trying” to propagate themselves better. They’re the result of weird monkeys doing artificial selection across millenniums. Or even through the centuries, as this Renaissance painting shows:
Check the bottom right - those are watermelons. Granted, watermelons aren’t from trees, but the reasoning is the same - in just three centuries or so watermelons went from “90% styrofoam with some good bits” to big balls of juice. Why? Human intervention.
How do they know it worked/failed.
A lot of answers here, but I think what’s still missing is the most intuitive. The plant that sent the seed doesn’t know, rather its offspring does - by simply surviving. The species as a whole “knows” by whatever works.
It’s the same as any other evolutionary process. Those who survive and reproduce the most carry their genes to the next generation; those who are less well adapted don’t reproduce as much and over the generations their genes get removed.
Say you have a bush with berries. Some bushes make sweeter berries than others. Let’s say those with the sweetest berries will attract more birds and animals who will eat the berries and scatter the seeds further away. The sweeter bushes are getting more lotto tickets for the next generation, the sour ones not so much. Repeat over time and eventually the sour ones will be gone.
The same can be applied to any other trait. It depends on the pressure of the environment they live in.
There is no knowing or feedback.
Mutations are random and there are many more failed mutations than successful ones.
You only see the successful species for that very reason, the failed ones have not been able to compete or pass their genes on at an appropriate rate.
the failed ones have not been able to compete or pass their genes on
Well, that’s feedback.
That the feedback mechanism that makes the process work. What is hard to understand is that it “informs” a population, not any individual.
It’s feed back only in the sense that it can be observed as a success or a failure by an independent party.
It’s not like a tree can see that last year’s seeds weren’t very good and try a different mutation this year.
Genes are not self aware, they do not have an end goal and their survival simply comes down to chance.
I’m with you. My wife has REALLY gotten into plants in the last year or so, and it amazes me how “smart” they are.
Obviously, everyone here is right. There is no intelligence, just genetics, but watching my morning glory wall climb the rope net to the roof of the house just blows my mind.
It’s crazy to think about all the trial and error over the centuries that it took for a simple flower to develop little sensor hairs that explore its surroundings and wrap itself around anything in range.
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