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.
Diatoms acquired photosynthesis after the evolution of the chloroplast. Diatoms, photosynthesis protists that live in the ocean, possess strange chloroplasts with four membranes instead of two. The leading hypothesis explaining this is that the chloroplasts in diatoms actually represent eukaryotic cells that formed symbiosis with the diatoms. The inner two membranes represent the membranes of the regular chloroplasts contained in this symbiotic cell. The outer two membranes represent the plasma membraned of the symbiotic cell and the food vacuole it was trapped in.