Do homologous structures point to a common ancestor?

In each transformation of energy , some energy what?

Asquirrel population lives in an area. over many years, a river in that area grows wider and stronger, eventually forming a canyon. the squirrel populations on the two sides of the canyon can no longer mate with each other and ultimately form distinct species. this is an example of

What type of plant is good for a bioassay and where can i buy it? i only have a month.