First living things on land clarification | Cosmology & Astronomy | Khan Academy | Summary and Q&A

TL;DR

Animals were the first to colonize land, followed by algae, and then fully land-dwelling plants.

Key Insights

• 🫤 Algae colonized land before any other organisms, approximately 1.2 billion years ago.
• 🫤 Animals that spent most of their time in the ocean started moving onto land around 530 million years ago, possibly for reproductive purposes.
• 🫤 The first plants to exclusively live on land appeared around 475 million years ago, based on spore fossils.
• 🏴󠁧󠁢󠁳󠁣󠁴󠁿 The first fossil of a true land animal, Pneumodesmus newmani, was discovered in Scotland and is approximately 428 million years old.
• 🌱 Whether animals or plants were first on land depends on how we define and categorize them.
• 🏆 Algae can be considered the winner if we classify them as plants, while animals win if we consider organisms that spent part of their life on land.
• 💦 The coastal area served as a transitional zone for organisms moving from water to land.

Transcript

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Questions & Answers

Q: What is the difference between algae and cyanobacteria?

Cyanobacteria, often referred to as blue-green algae, are actually bacteria. Algae, on the other hand, is considered eukaryotic and lacks the structures of modern plants.

Q: Why did animals start colonizing land before plants?

Animals may have ventured onto land to lay eggs because there would have been fewer predators present. Land provided a safer environment for laying eggs compared to the ocean.

Q: What is the oldest known fossil of a true land animal?

The oldest known fossil of a true land animal is called Pneumodesmus newmani and was discovered in Scotland. It is approximately 428 million years old.

Q: What were the first creatures to live entirely on land?

The first fully land-dwelling organisms were plants, which appeared around 475 million years ago based on fossil evidence of their spores.

Summary & Key Takeaways

• Algae colonized coastal rocks approximately 1.2 billion years ago, making it the earliest organism to move onto land.

• Animals that spent most of their time in the ocean started showing up on land approximately 530 million years ago, possibly to lay eggs in a protected environment.

• The first plants to fully live on land appeared around 475 million years ago, based on fossil evidence of their spores.