1. Summary

This video explains a multitude of topics ranging from how the Earth was formed, early life on Earth, the first Ice Age and when life really began. It starts off from the beginning of Earth’s creation, and takes us through the steps of time towards the explosion of life in the Palaeozoic Eon, known as the Cambrian Explosion. It explains how Earth obtained atmospheric oxygen, and what the first ever life on Earth was like.

2. Why Watch This Video?

1. Have you ever wondered what the first life on Earth was like?
2. Would you like to know how Earth came to be as it is today?
3. Have you ever been confused about the development of life on Earth?

3. Key Terms

Cyanobacterium: bacteria that get their energy from sunlight through the use of photosynthesis. They were also the first life on Earth!

Hadean Eon: a geological eon that began at the formation of the Earth, named after “Hell” or “Hades.” Lasted 600 Million years.

The Great Oxygenation Event: the introduction of oxygen into Earth’s atmosphere. It was caused by cyanobacteria through photosynthesis, releasing oxygen into the Earth’s atmosphere.

4. Loose Ends

Loose end #1: The development of the Earth happened over the course of billions of years, even though the video makes it seem like it quickly happened without interruption. Keep in mind the Earth is 4.5 billion years old! Try imagining the Earth’s timeline as a 24-hour clock… The Hadeon eon began at 00:00, while the first appearance of life only appeared sometime around 04:00. It wasn’t until 21:00 that the Cambrian Explosion began. For us modern humans, we only appear at 23:59:59, meaning in the last second!

Loose end #2: After the Cambrian Explosion life did develop quickly, yet not as instantaneous as the video portrays. The word “explosion” is used to dramatize the extensive amount of life and diversity, as well as the sudden appearance of life.

Loose end #3: It is not 100% known how the moon formed, and this video only goes over some hypotheses. One hypothesis is that a large asteroid body grazed the Earth sometime around the late Hadeon eon, and got caught in the Earth’s gravitational field, causing it to orbit the Earth. Another hypothesis is that a body the size of Mars crashed into Earth, and the debris that was thrown into space from the collision coalesced to form the moon. With the moon orbiting the Earth, the planet’s rotation slowed down, which is why there are 24 hours in a day and why the Earth has seasons.

5. Self-Test Questions

Question 1: The first life on Earth was…
Answer a: Lizards
Answer b: Fish
Answer c: Microscopic animals
Answer d: Cyanobacteria

Question 2: How did Earth’s atmosphere gain oxygen?
Answer a: Gas releasing from rocks
Answer b: Asteroids impacting the Earth
Answer c: Cyanobacterium through photosynthesis
Answer d: Oxygen was always in the atmosphere

Question 3: What was the first eon on Earth?
Answer a: Hadean Eon.
Answer b: Archean Eon.
Answer c: Proterzoic Eon.
Answer d: Phanerozoic Eon.

Question 4: How long did the first ever ice age last?
Answer a: 1000 years.
Answer b: 50 million years.
Answer c: 300 million years.
Answer d: 2000 million years.

Question 5: When did the Cambrian Explosion (Palaeozoic Era) occur?
Answer a: 541 million years ago.
Answer b: 4 billion years ago.
Answer c: 10.7 trillion years ago.
Answer d: 20.5 million years ago.

6. Answers to Self-Test Questions

1. Answer D is correct due to the fact that cyanobacteria were the first forms of life, while all other forms of life appeared after.

2. Answer C is correct because Earth only gained its oxygen through the use of photosynthesis by cyanobacterium.

3. The correct answer is A because the first eon on Earth was the Hadean Eon, named after “Hell” or “Hades” due to its climate.

4. Answer C is correct because the first ice age lasted for 300 million years.

5. The answer is A because the Cambrian Explosion occurred 541 million years ago, during the Palaeozoic Era.