Understanding Calcium Carbonate in Marine Life

The video explores the formation and composition of pearls and other marine structures, focusing on calcium carbonate's role. It explains how mollusks use this compound to build diverse shells and introduces nacre, a strong biomaterial. The process of pearl formation is detailed, highlighting mollusks' defense mechanisms.

What is the primary material that pearls and other marine structures are made of?

• Silicon dioxide

• Calcium carbonate

• Sodium chloride

• Magnesium sulfate

How does calcium carbonate form such a variety of materials?

• Through the addition of other elements

• By changing its chemical composition

• By being woven together in various shapes

• Through different chemical reactions

What organ in oysters secretes the organic matrix to construct a scaffold for the shell?

• Radula

• Mantle

• Gills

• Foot

What do mollusks use to attract and guide calcium carbonate molecules into layers?

• Enzymes

• Charged proteins

• Lipids

• Carbohydrates

What are the two crystal structures that mollusks can produce from calcium carbonate?

• Mica and olivine

• Gypsum and halite

• Calcite and aragonite

• Quartz and feldspar

Which crystal structure is more stable and less prone to dissolving over time?

• Aragonite

• Calcite

• Quartz

• Gypsum

What is the special form of aragonite that is stronger and more versatile?

• Gypsum

• Nacre

• Calcite

• Quartz

What causes the iridescence in nacre?

• The absorption of ultraviolet light

• The presence of organic pigments

• The presence of metallic elements

• The thickness of the layers being similar to the wavelength of visible light

What triggers the formation of a pearl sac in mollusks?

• Exposure to sunlight

• A lack of calcium in the water

• An intruding parasite or particle of sand

• A change in water temperature

What is the leading theory for why mollusks make pearls?

• To attract mates

• To store nutrients

• As a defense mechanism

• To regulate buoyancy