Why are platypus, brown bear, lion, and house cat thought to be related to each other?

Ablastocyst is a group of cells that forms after a human egg is fertilized. the blastocyst consists of two types of cells. some of these cells will become the placenta. what do the other cells develop into?

Compare and contrast region e in the illustration above with region d. describe the physical characteristics of each region.

Sea stars, sea urchins, sand dollars, and brittle stars are all memeber of a group, what is the common name of the group they are all in