What are these organisms called that have two halves that fit together like the top and bottom of a petri dish and get smaller and smaller over time when they reproduce asexually

Diatoms

Explanation:

Diatoms are a group of algae especially found in the oceans (they also live in waterways and soils). The diatoms are known to generate about 25% oxygen on the Earth and 50% of the organic mass in the oceans. The shell of the diatom is composed by two halves or valves that overlap each other like petri dish halves, where the upper valve (epitheca) fits over the lower valve (hypotheca). Diatoms reproduce by both sexual and asexual (vegetative) reproduction. In vegetative reproduction, a single cell divides by mitosis and each daughter cell receives one valve.

ionic bonds are two oppositely charged ions that attract. a sodium ion has a 1 positive charge; a chloride ion has a 1 negative charge. sodium and chloride have oppostive charged ions that attract which forms an ionic bond. a chemical bond formed when two atoms share electrons is called