Plant Evolution

Cyanobacteria kept producing oxygen through photosynthesis, gradually transforming Earth's atmosphere into the oxygen-rich air we know today. This massive change laid the foundation for all later life on Earth.

An oxygen-using bacterium (an alpha-proteobacterium) moved inside another cell and eventually became the 'mitochondrion' — the powerhouse of the cell. This was the beginning of eukaryotes, the cells with nuclei from which all plants and animals descend.

A photosynthetic bacterium (a cyanobacterium) was taken inside a cell that already had mitochondria, and became the 'chloroplast.' This was the very moment that the ancestor of all plants was born.

There was a time when nearly the entire Earth — even the equator — was covered in ice. It was a tough crisis for life, but after surviving the freeze, multicellular organisms exploded in diversity.

Green algae living in water evolved the ability to survive on land. This was the great 'invasion of the land' by plants.

Plants with internal 'pipes' (vascular tissue) for transporting water and nutrients appeared, allowing plants to grow much larger.

Plants with seeds appeared for the first time. Seeds can survive dry conditions and travel far, helping plants spread to every corner of the land.

Gymnosperms—plants like pines and cedars that bear exposed seeds without fruit—thrived on a massive scale. During the age of dinosaurs, these plants covered the land.

Plants with flowers and seeds enclosed in fruit appeared seemingly out of nowhere. By partnering with insects and birds for pollination, they multiplied rapidly and now make up most of the greenery on Earth.

Flowering plants split into two major groups: monocots (grasses, lilies) and eudicots (roses, daisies). They differ clearly in leaf vein patterns, seed structure, and more.

The most primitive group of land plants—those without internal water-transport tubes—diversified. They still thrive in moist habitats today.

Ferns—seedless plants that reproduce by spores—flourished greatly. In the Carboniferous, giant tree ferns up to 30 meters tall formed vast forests. Their dead remains piled up underground and eventually became coal.

Cycads—palm-like plants—appeared on the scene. They thrived so greatly during the age of dinosaurs that the era is sometimes called the 'Age of Cycads.' About 300 species survive today as living fossils in tropical and subtropical regions.

The ginkgo family, known for their fan-shaped leaves, appeared. Once containing many species, today only a single species survives—a true living fossil.

The oldest lineages within flowering plants branched off. These include plants like lizard's tail and magnolias, which have relatively simple flower structures.

A group containing many familiar plants—roses, beans, oaks, maples—exploded in diversity.

The asterid group—including daisies, nightshades, and coffee plants—diversified. They evolved fused petals and specialized flower structures like the composite head.

The grass family—including rice, wheat, and corn—appeared. As grasslands later spread across continents, grazing animals like horses and cattle evolved, and grasses ultimately became the foundation of human agriculture.

Plant roots and fungi formed a partnership called 'mycorrhiza,' clearly preserved in fossils. Plants get nutrients, fungi get sugars — a mutual help that powered the colonization of land.

True trees over 10 meters tall appeared on Earth for the first time. *Archaeopteris* spread deep roots and completely transformed the landscape.

Vast forests of giant ferns and tree ferns covered Earth, and their remains piled up to become coal. Atmospheric oxygen rose to about 30% — higher than today — and giant insects flew through the skies.

The worst extinction event in Earth's history wiped out about 90% of marine species. Land plant communities were reset, and afterwards the age of cycads and conifers began in earnest.

A giant asteroid struck the Yucatán Peninsula in Mexico, ending the age of (non-avian) dinosaurs. In the plant world, ferns briefly bloomed everywhere (the 'fern spike'), and afterwards angiosperms spread even further.

Some grasses invented a new 'C4' photosynthesis pathway that works efficiently even in hot, dry places. This created savannas and prairies, setting the stage for horses and zebras to evolve.

Modern humans (Homo sapiens) appeared in Africa. Using tools and cooperating in groups, they eventually spread across the entire world.

Humans began cultivating wild plants, growing crops such as wheat and barley. This led to a population explosion and the birth of cities and civilizations.