How plants moved from sea to land and changed Earth forever
Long before dinosaurs roamed the earth, the Earth was very different from the planet we know today. About 500 million years ago, most of the Earth’s surface was bare rock and dry soil. There were no trees, no grass, no flowers. Life existed almost entirely in the oceans.
Then something amazing happened: plants began to grow on land.
This moment was one of the most important events in Earth’s history because it changed the planet forever. As a geoscientist, I am interested in changes in the diversity of flora and fauna, that is, plants and animals, over time.
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The predecessors of plants lived in water
The history of plants begins in water. The first plant organisms were simple, tiny green life forms such as algae. Even today, algae can be seen in the form of algae along beaches or as green slime on the rocks of ponds.
Algae has lived in Earth’s oceans and lakes for over a billion years. They can prepare their own foodusing sunlight, water and carbon dioxide to create sugars. This process is called photosynthesis; it releases oxygen – the gas we need to breathe – as a byproduct.
At first, the Earth’s atmosphere contained very little oxygen. Over millions of years, photosynthetic organisms like algae and some bacteria slowly released oxygen into the air. This change, sometimes called the Great oxygenation eventallowed larger, more complex life to evolve. Without oxygen-producing organisms, animals, including humans, could never have existed.
Scientists believe THE the first true plants evolved from green algae about 470 million years ago. These early plants lived in shallow waters near shorelines, where conditions changed often. Sometimes they were underwater and sometimes exposed to air. This habitat helped them slowly adapt to life on land.
Getting settled on land was not easy. Aquatic plants are supported by water and can easily absorb nutrients, but land plants have faced new challenges. How could they avoid drying out? How could they stand without floating? How could they get water and nutrients from dry soil?
To survive, the first plants developed important new characteristics. A key adaptation was a waxy covering, called cuticlewhich helped keep water inside the plant. Plants have also developed stronger cell walls that allow them to resist gravity. Simple root-like structures called rhizoids helped anchor plants to the soil and absorb water and minerals. from the ground.
The first land plants were very small and simple. They looked like modern moss, hepatic and hornworts, which still grow today in moist places like forest floors and stream banks. These plants had no real roots or stems and stayed close to the ground. Fossils of early land plants, such as Cooksoniadate back about 430 million years and feature small, branched stems only an inch or two tall.
Even though these plants were tiny, they had a huge impact on Earth. As the plants spread across the ground, their roots helped break up the rocks and turn them into soil, a process called aging. This created richer soil capable of supporting more life.
Plants also release more oxygen into the atmosphere, improving air quality and helping animals breathe. Plants created new habitats and food sources, allowing insects and other animals to move from water to land.
Increasing complexity over millions of years
Once plants became established on land, evolution continued. About 420 million years ago, plants evolved vascular tissue: tiny tubes that transport water and nutrients throughout the plant. This adaptation allowed plants to grow taller and stronger because water could rise from the roots to the leaves. These vascular plants included the early relatives of ferns and club mosses.
Thanks to vascular tissues, plant life truly began to flourish. About 360 million years ago, vast forests covered much of the Earth. Giant ferns and tree plants, some over 30 meters tall, dominated the landscape. Over time, the dead plant material from these forests was buried and compressed, eventually form coalwhich people still use as a source of energy today.
Another major step in the evolution of plants was the seed developmentabout 380 million years ago, found in seed ferns. Other seed plants, like the first conifers – a group that includes modern pines – could reproduce without needing water for fertilization. Seeds protected plant embryos and allowed plants to survive harsh conditions like drought or cold.
The most recent major plant evolution occurred about 140 million years ago, when flowering plants, what scientists call angiospermsappeared. Flowers helped plants attract animals like insects and birds, which spread pollen and seeds. Fruits developed to protect seeds and help them travel. Today, flowering plants make up most of the plants we see, including trees, grasses, fruits and vegetables.
The first plants not only survived; they transformed the Earth. They changed the atmosphere, built the soil, and created ecosystems for animals to thrive on land. Thanks to the evolution of plants, Earth has become a green and living planet, full of diverse life.
This edited article is republished from The conversation under Creative Commons license. Read the original article.
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