How Blood Evolved (Many Times)

Summary

The video explores the evolutionary history of blood, tracing its origins back to the ancient arthropod Marrella splendens, whose fossils reveal the earliest evidence of blood-like substances. It discusses how blood functions in transporting oxygen and nutrients, noting that not all animals require blood. The narrative highlights the evolution of different blood proteins, such as hemoglobin and hemocyanin, each adapted for various environments. The story emphasizes the significance of blood in the complexity of life, showcasing how evolutionary changes have led to the diverse blood types seen in modern animals.

Takeaways

• 😀 The Burgess Shale in British Columbia contains over 30,000 fossils of Marrella splendens, an ancient armored arthropod.
• 😀 Many Marrella fossils exhibit black stains, which are the earliest evidence of blood in the fossil record.
• 😀 Blood has evolved significantly over 500 million years, adapting to the needs of increasingly complex and active animals.
• 😀 Not all animals require blood; simpler organisms like sponges and jellies use diffusion for nutrient transport.
• 😀 The common ancestor of all blood-circulating organisms likely existed over 600 million years ago.
• 😀 Early blood proteins may have evolved as long as 740 million years ago, initially serving various metabolic functions.
• 😀 Hemoglobin, the main oxygen-transport protein in many animals, is responsible for the red color of vertebrate blood.
• 😀 Marrella utilized hemocyanin, a copper-based oxygen transport protein, resulting in blue blood, unlike iron-based hemoglobin.
• 😀 Convergent evolution led to different oxygen-carrying proteins like hemerythrin and biliverdin in various species.
• 😀 The Ice Fish of Antarctica lacks hemoglobin entirely, resulting in clear blood, adapted to cold, oxygen-rich environments.

Q & A

What significant discovery was made in the Burgess Shale related to Marrella splendens?

Fossils of Marrella splendens were found, revealing over 30,000 specimens that are more than 500 million years old, some of which show black stains thought to be early evidence of blood.

How does blood function in more complex animals?

Blood supplies oxygen to tissues, carries nutrients to cells, and removes waste, allowing more complex and active organisms to thrive.

What are some animals that do not need blood, and why?

Simple animals like sponges, sea anemones, and jellies can diffuse oxygen directly from water into their cells, negating the need for a circulatory system.

What characteristics do all animals with a blood circulatory system share?

They typically exhibit bilateral symmetry and possess an internal body cavity to support and cushion internal organs.

What was the role of blood proteins in early organisms?

Early forms of blood proteins likely served various functions, such as metabolizing nitric oxide or trapping oxygen before evolving to transport oxygen.

How does hemoglobin function in vertebrates?

Hemoglobin binds to iron and transports oxygen from the lungs to tissues, giving vertebrate blood its red color.

What is hemocyanin, and how does it differ from hemoglobin?

Hemocyanin is an oxygen-carrying protein that uses copper instead of iron, giving the blood a blue color; it evolved independently of hemoglobin.

Why do some animals retain both hemocyanin and hemoglobin?

Having both proteins may provide flexibility in oxygen transport, allowing organisms to adapt to varying environmental conditions.

What are some other blood proteins besides hemoglobin and hemocyanin?

Other blood proteins include hemerythrin, which uses iron but lacks the heme structure, and is used by some marine worms and brachiopods.

What is unique about the blood of Ice Fish?

Ice Fish have clearish white blood because they lack hemoglobin and other proteins, which helps prevent clotting in cold environments.