Life in the Ocean

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Coral reef ecosystems, like the one shown here, are the most biodiverse habitats in the ocean. Despite covering only 2% of the ocean floor, they provide a home for approximately 25% of all marine species.

The ocean is vast. It covers over 70% of the Earth’s surface and extends to depths that make the tallest mountains seem minuscule. The ocean formed as the Earth cooled billions of years ago and it continues to evolve and change today. The ocean is so immense that it impacts daily weather and controls the global climate, making much of the planet able to sustain life.

The greatest species diversity is found in the ocean, spread across habitats ranging from deep-water vents to estuaries where fresh and saltwater meet. While the ocean has been used as a resource for food and travel since humans learned to sail, there is still much to discover.

Enter a world where brightly-colored fish dart about in the crystal clear waters of a tropical reef and the largest animal on Earth, the blue whale, is free to navigate the globe.

Dive in to explore the astounding diversity of marine species!

Investigating the Life in the Ocean will help you to:

identify marine organisms based on their characteristics.
understand the evolutionary history of marine organisms.
describe how marine organisms are classified.

ABOUT THE AUTHOR

Catherine “Cathy” Christopher has always been passionate about science, with a special love for marine biology.. While she once dreamed of studying whales, her fascination quickly shifted to the incredible world of invertebrates during her undergraduate studies at Bowling Green State University. She later earned her Master’s in Biology from Florida Atlantic University, where she also became scuba certified and gained hands-on experience with sea turtles, birds, and everything in between.

Cathy’s career has spanned from developing engaging K-12 science curricula to leading educational initiatives that make marine science accessible to learners of all ages. When she’s not crafting the next great science lesson, Cathy can be found underwater, exploring reefs across the Caribbean and Indo-Pacific. A certified dive instructor since 2017, she loves pointing out unique marine invertebrates and is always happy to help fellow divers identify their latest underwater finds.

Explore the entire course below. When you are finished with each section, close the window to return here.

Life in the Ocean - An Overview

Life in the Ocean - Vertebrates

Life in the Ocean - Invertebrates

Life in the Ocean - Plants and Algae

Supplemental Resources