Plants appeared on land over 500 MYA. The way had been paved by hardier life. The first soils were prepared by microbes, algae, and lichen that had arrived much earlier. They broke down rock to sustain themselves, releasing minerals valuable to vegetative growth.
Plants played out what their predecessors had started. Rock-hugging mosses extracted vital minerals from the substrate upon which they were perched, causing chemical weathering on the Earth’s surface. These terrestrial pioneers paved the way for a richer life for their descendants.
The earliest plants had help from microbes that garner minerals from the soil. This grew into mutual relations. Plants today cultivate specific root microbes when growing in nutrient-poor soil.
From humble beginnings, plants evolved with verdant flourish. Ferns emerged over 360 MYA.
Ferns were initially quite successful. Like sharks, ferns had a divine design that kept them in good stead for hundreds of millions of years. The evolutionary advance of ferns was modest for 180 million years.
Then calamity struck. Unlike sharks, ferns could not compete with more modern designs. The rise of towering trees and flowering plants spelt their demise.
Desperate for an innovation to save them from the darkness of extinction, ferns found the answer in learning to live in the shadows of more advanced plants. Moving forward took looking back.
Ferns picked up a gene from an earlier-evolved plant – hornworts – that let them thrive on shady forest floors. From 180 mya, the 1 lineage of ferns that had managed to survive proliferated into 12,000 species.
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Unlike later-evolved plants, ferns spawn not from seeds, but from a single type of spore. Spores mature into a plant that may be female, male, or hermaphroditic (both sexes).
If there are no other ferns around, the plant stays hermaphroditic and self-fertilizes; reproducing, but with less potential fitness from inbreeding. In contrast, a sexually reproducing population generates genetic diversity, which abets population survival in a changing world, which is why sex evolved in the first place.
Ferns decide their sex based upon interplant communication, mediated by chemical signals. Early-maturing ferns in a growing population, knowing that there are nearby neighbors that will also produce spores, often choose to be female. (Why early ferns mainly select the superior sex is not known.)
After producing spores, ferns seed the surrounding ground with hormones that selectively tell the next generation what sex they should be. Ferns manage this chemical messaging at just the right time and place to produce an optimal ratio of females and males, thus maximizing genetic diversity and population growth potential. While chemical signals are the medium by which this communication transpires, there is no material explanation for how ferns know to produce optimum outcrossing (sex ratio) within their population. Certainly, a mathematical calculation is involved.
Plants are master molecular constructionists. They can concoct formulas for every purpose: sugary confections to entice cooperation, scents to deceive, and poisons to ward off predation.
“The untamed native plant is a pugilist: feeding others is not its raison d’etre. Defensive toxins lace the tissues of many plants.” ~ American ecologist Ian Baldwin
Goldenrods & Gallflies
“Gallflies strongly reduce a goldenrod’s fitness by decreasing the number of seeds it produces, as well as the sizes of those seeds. That’s because when the plant’s tissues are damaged by the insect, it diverts its energy away from seed production.” ~ American entomologist John Tooker
Goldenrods are especially bothered by gallflies, whose entire life cycle is centered around the flowering plant. The goldenrod has figured out how to put the parasite off.
A goldenrod sniffs out when a male fly is about. Yes, plants can smell.
“Goldenrod plants are sensitive to even small concentrations of this compound.” ~ John Tooker
That little parasite is probably trying to find a mate: sitting atop a leaf or bud, dancing when a female comes into view. Such insolence is not to be borne. The goldenrod rolls up the welcome mat by producing toxins that deter egg-laying.
Goldenrods offer one of innumerable examples of inscrutable knowledge behind adaptation. Only by Nature’s grace could a plant possibly know what molecular combination effectively deters egg-laying by its nemesis. Many plants produce compounds (secondary metabolites) that specifically target molecular mechanisms essential to a tormenter’s development, metabolism, or reproduction.
“Of course, it makes sense that evolution has used all the available opportunities to enhance plant fitness.” ~ English botanist Beverley Glover
In studying the history and web of life, an intelligent force behind adaptation is everywhere apparent. The combinations by which life’s goals are met are often subtle and complex. Flowers’ mastery over physical forces illustrate.