The Colonization of Land

Over three and a half billion years ago, lifeforms could survive only in aquatic environments. Later, some prokaryotes, such as cyanobacteria, began fixing carbon dioxide to produce sugars through photosynthesis.

These photosynthetic organisms released oxygen, and it accumulated in the atmosphere.

Evidence suggests that single-celled photosynthetic microbes colonized moist terrestrial surfaces more than two billion years ago.

While land environments provided abundant sunlight and carbon dioxide, two crucial components for photosynthesis, they also presented challenges such as desiccation, UV exposure, and lack of structural support.

Multicellular plants and fungi gradually evolved the ability to live on land around 470 million years ago.

This transition required several adaptations. Some cells formed shoots that capture light, while others formed root-like structures that anchor the plant and absorb water and nutrients.

Other structural changes also helped plants survive on land. For example, a waxy cuticle limited evaporation.

Cell walls provided structural support, while vascular tissue helped move water through larger plants.

Around 450 million years ago, arthropods were the first anima