Activity: Diversity

“Diversity” can be expressed in several ways:

Taxonomic diversity usually is expressed as the number of taxa (species, genera, or families) in a given area. The taxonomic category “family” (which in zoology always ends in -idae) groups bivalves with similar morphologies and lifestyles. For example, species in the family Veneridae have round or oval shells, usually relatively smooth (without spines), that are heart-shaped in anterior view, and that have siphons to live below the surface of the sand (evidenced by the pallial sinus). There are approximately 100 families of bivalves living today, with approximately 20,000 living species. The fossil record is equally large. Using books, the internet, and/or specimens in your classroom or that you can collect on a field trip, ask your students to identify representatives of bivalve families.

Ecological diversity reflects the different ways that organisms interact with their environment.

Diversity of habitat:

• Bivalves that live below the sand (Hard-shelled Clam, Soft-shelled Clam, Freshwater Mussels, Lucine Clams).
• Bivalves that live on top of the sand (Scallops), or that cement or use a byssus to attach to rock (Arks).

 

Diversity of protection against predators:

• Bivalves that burrow below the sand to hide (Hard-shelled Clam, Soft-shelled lam, Freshwater Mussels, Lucine Clams).
• Bivalves that clamp tightly closed (Arks, Hard-shelled Clam).
• Bivalves that are thick-shelled and resistant to cracking by predators (Hard-shelled Clam, Freshwater Mussels, Oysters).
• Bivalves that are thin-shelled but can swim to escape (Scallops).
• Bivalves that live gregariously, tightly crowded together on rocks (Mussels, Oysters).

 

Notice that some species use several anti-predator tactics. Discuss these adaptations with your students and ask them to think of anti-predator tactics of other animals or plants.

See also the Activity Reading Empty Shells.