33.7
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 animals to evolve the ability to live on land.
These organisms had external skeletons and belonged to the group that includes modern insects, arachnids, and crustaceans.
Early tetrapods evolved around 380 million years ago. Their lobe-finned fish ancestors had features like lungs and stronger limb bones that helped them move from water onto land. They later diversified into amphibians, reptiles, birds, and mammals.
Plants that had already colonized land formed the base of early terrestrial food webs, supporting both arthropods and tetrapods. Through this gradual process, plants, fungi, and animals colonized Earth’s landmasses and eventually evolved into the diverse species that exist today.
Changes in the environment of the early Earth drove the evolution of organisms. As prokaryotic organisms in the oceans began to photosynthesize, they produced oxygen. Eventually, oxygen saturated the oceans and entered the air, resulting in an increase in atmospheric oxygen concentration, known as the oxygen revolution approximately 2.3 billion years ago. Therefore, organisms that could use oxygen for cellular respiration had an advantage. More than 1.5 years ago, eukaryotic cells and multicellular organisms also began to appear. Initially, all of these species were restricted to the oceans of Earth.
The first organisms to live on land were photosynthetic prokaryotes that inhabited moist environments near ocean shores. Despite the lack of water, terrestrial environments offered an abundance of sunlight and carbon dioxide for photosynthesis. Around 500 million years ago, the ancestors of nowadays plants were able to colonize drier environments, but they required adaptations to prevent dehydration. They developed methods for reproduction that did not depend on water and protected their embryos from drying out. These early plants furthermore evolved a vascular system that included roots to acquire water and nutrients and a shoot to obtain sunlight and carbon dioxide.
Plants and fungi appear to have colonized land at the same time. Their coevolution onto land is the result of the mutually beneficial relationship between many plants and fungi, seen in both modern organisms and some of the earliest plant fossils; Fungi aid in the absorption of nutrients and water while benefiting from the nutrients provided by the plant.
Arthropods were the first animal species to colonize land, around 450 million years ago. The first tetrapods later evolved to live on land as well, finding an abundance of food in the plant species that had colonized the land. Amphibians dominated terrestrial animal life for 100 million years. Later, dinosaurs and then mammals would become the most abundant terrestrial animals.
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 animals to evolve the ability to live on land.
These organisms had external skeletons and belonged to the group that includes modern insects, arachnids, and crustaceans.
Early tetrapods evolved around 380 million years ago. Their lobe-finned fish ancestors had features like lungs and stronger limb bones that helped them move from water onto land. They later diversified into amphibians, reptiles, birds, and mammals.
Plants that had already colonized land formed the base of early terrestrial food webs, supporting both arthropods and tetrapods. Through this gradual process, plants, fungi, and animals colonized Earth’s landmasses and eventually evolved into the diverse species that exist today.
From Chapter 33:
Now Playing
33.7 : The Colonization of Land
Evolutionary History
32.1K Views
33.1 : Conditions on Early Earth
Evolutionary History
68.0K Views
33.2 : What is Evolutionary History?
Evolutionary History
31.9K Views
33.3 : The Fossil Record
Evolutionary History
23.6K Views
33.4 : The Evidence for Evolution
Evolutionary History
41.5K Views
33.5 : Phylogenetic Trees
Evolutionary History
42.5K Views
33.6 : Convergent Evolution
Evolutionary History
29.1K Views