Rethink Ancient Predators

Sharks and rays have been around for over 450 million years, but they are some of the most advanced—and endangered—of all vertebrates.
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Authoring Scientists

Marcelo Carvalho
Dr. Carvalho studies the anatomy and systematics of sharks and rays.
Ian Harrison
Dr. Harrison is an ichthyologist with a Ph.D. from the University of Bristol.

About the Course

Long featured in myths and legends, sharks may be one of the most readily recognized marine species. But did you know that rays are one of their closest relatives? Join Museum scientist Dr. Marcelo Carvalho in his study of fossil and living sharks and rays to find out how they're related, how they navigate in the dark seas, what other extraordinary sensory and reproductive features are shared by sharks and rays, and why shark conservation is critical. Read more.

Key Science Concepts

Sharks and rays are ancient, first appearing about 450 million years ago.

Sharks and rays may have the most advanced sensory systems—hearing, smelling, vision and electrical sensing—of all vertebrates.

As top predators, sharks and rays maintain the stability of many marine ecosystems.

In general, rays live on the bottom of the ocean and sharks in open water. A continuum of body shapes and lifestyles reflects the adaptation of these cartilaginous fish to a range of environments.

Scientists study the form and structure of fossils and living organisms in order to determine the diversity and evolutionary relationships of species.

Shark and ray reproduction varies, with some species laying eggs and some giving birth to live young.

Many shark and ray populations are endangered. All reproduce rather slowly, which makes them vulnerable to threats such as overfishing and the destruction of coastal breeding areas. Conservation efforts are underway, but populations are difficult to manage because much about these fishes remains unknown.

Course Textbook

Sharks in Question
Author: Victor G. Springer and Joy P. Gold
Publisher: Smithsonian Institution Press
Edition: April 1989
Paperback: 192 pages
ISBN: 0874748771
Buy online: Amazon

Graduate Credit

This course is approved for graduate credit and continuing education units from leading institutions at an additional cost. Read more.

Adams State UniversityCity University of New YorkFramingham State UniversityHamline UniversityNorthwest Missouri State UniversityWestern Governors University

Related Courses

Interested in more from Seminars on Science? Consider these related offerings:

In the Field with Spiders
Classification, Anatomy and Morphology
The Diversity of Fishes
Classification, Anatomy and Morphology

Course Preview

Watch a video about electric rays, read about the fossil record, and explore shark anatomy in 3-D.

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