Science & Technology

Earth began as mostly bare rock and dry soil, but early forms of life in water evolved into lush green landscapes.

Earth has existed for more than 4 billion years, but plants have not always been around. At first, the Earth’s surface was mostly bare rock and dry soil, an environment not conducive to plant growth. Over time, however, that began to change. Plants evolved from flourishing in water to land, leading to the green, lush, and beautiful Earth we know today.

From the Water They Grew

The earliest forms of life began in Earth’s oceans with simple, single-celled organisms such as bacteria and archaea. Eventually, plant-like organisms, such as algae, began to form in the water and slowly made their way to land. Using photosynthesis – a process in which plants convert sunlight, water, and carbon dioxide into sugar and oxygen that provides energy for life on Earth – plants evolved to thrive out of the water. This evolutionary process is believed to have started about 470 million years ago.

This transition led to the Great Oxygenation Event, making it possible for larger organisms such as plants, animals, and humans to live on Earth. But before all of that, some changes happened to the algae that lived on shorelines and the edges of other bodies of water. Constantly changing conditions led those plants to survive both underwater and outside of the water. Among the obstacles facing plants  were learning how to stay hydrated and how to stand without the support of water.

The first change was the development of a waxy outer coating called a cuticle, that would help hold water, keeping the plant from drying out and dying. The second adaptation was stronger cell walls that allowed the plants to stand upright against the forces of gravity. Root-like appendages called rhizoids would extend into the ground, gathering much-needed nutrients and water from the soil. Next was the adaptation of vascular tissue or tiny tubes that allowed nutrients to be transported throughout the entire plant. From there, the plants continued to get larger and stronger. They were releasing even more oxygen into the atmosphere, and the roots were breaking down the rocky ground to reach more nutrient-rich soil for new, more complex plant life to grow.

Seeds and Ferns

Scientists believe that the first seeds were introduced around 380 million years ago. They came from conifers – evergreen plants and trees – and protected the plants’ embryos and allowed them to be fertilized without the presence of water. That meant the seeds could survive severe weather conditions such as drought and extremely cold temperatures.

A bit later, after the plants developed vascular tissue, much larger plants began to grow. Around 360 million years ago, giant ferns and other tree-like plants began to make their debut. Some of these reached more than 100 feet tall and overran specific areas. When they died, their remains were buried and compressed, eventually forming coal, an important energy source used by humans.

The evolution of plants continued when flowering plants, called angiosperms, were introduced approximately 140 million years ago. These attracted insects and birds, and they carried away the plants’ pollen and seeds, allowing them to grow in different areas.

The evolution of plants was a crucial stage in the development of animal life on Earth. Without them, humans and other living organisms could not exist.

1. Plants did not exist on Earth until about 470 million years ago.
2. Plants evolved from living in water to living on land, using a process called photosynthesis.
3. Without plant life, humans and animals could not exist.