Since ribosomes are found in bacterial cells, do ribosomes have a membrane around them? why or why not?

No. Ribosomes do not have a membrane. They are composed of 2 subunits - the small subunit is where the mRNA is read and the large subunit is where the amino acids are joined together to form the polypeptide (protein) - a membrane would interfere with this process. Plus, ribosomes are in both eukaryotes and prokaryotes - and prokaryotes have NO membrane bound organelles.

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation

explanation:

on disadvantage of hydroelectric power is the cost. another disadvantage of using hydroelectric power is finding a water source powerful enough to harvest hydroelectric power.