âI think weâve read every single book they have.â Mark chuckled. He still wasnât ready to put the children downâWill was hanging off of one hip, his hand on Markâs shoulder as he stoically looked down at Bridget, and Mabel had nuzzled into the crook of Markâs neck with a contented sigh.
Diatoms are producers within the food chain. A unique feature of diatom cells is that they are enclosed within a cell wall made of silica (hydrated silicon dioxide) called a frustule. These frustules show a wide diversity in form, but are usually almost bilaterally symmetrical, hence the group name.
The first diatoms â the centrics â appeared in the Jurassic age some 200 million years ago, as combinations of yeast-like organisms and algae. Over the eons,diatoms acquired new genes, shapes and complex metabolisms. Theyâve becomechampions of photosynthesis, while retaining many properties of animal cells. With other photosynthetic protists, they produce oxygen and absorb CO2. Over millions of years, diatom shells have sunk to the seabed, forming thick layers of silica and fossil fuels. 65 million years ago, diatoms survived the mass extinction of dinosaurs. They adapted to polar regions, where they still proliferate.