There are four types of Infectious Agents that can affect the human body. These are Viruses, Bacteria , Fungi, and Parasites. Viruses are Nonliving agents that infect a host's cells to reproduce rapidly. Vaccines are the best way to combat viral infections,
preventing them in the first place. Bacteria are usually single-celled organisms that get their nutrients from the environment
around them. Some bacteria are harmful, such as those that cause Strep throat, while others are beneficial, such as those that
help with the digestion of food. Fungi obtain nutrients from both living and nonliving sources outside of their bodies. Fungal
infections are typically treated with Anitfungal drugs and creams. Parasites live on or in a host organism and get their nutrients
from that organism. Typically, parasites do not kill the host, but they often make the host weaker.
Does this sound right. 

No need no need for this to happen

1.fossils 2.analogous organs 3.homologous organs

Proteins are the workhorses of the cell, controlling virtually every reaction within as well as providing structure and serving as signals to other cells. proteins are long chains of  amino acids  , and the exact sequence of the amino acids determines the final structure and function of the protein. instructions for that sequence are encoded in  genes  . to make a particular protein, a messenger ribonucleic acid (mrna) copy is made from the gene (in the process called  transcription  ), and the mrna is transported to the  ribosome  . protein synthesis, also called  translation  , begins when the two ribosomal subunits link onto the mrna. this step, called initiation, is followed by elongation, in which successive amino acids are added to the growing chain, brought in by transfer rnas (trnas). in this step, the ribosome reads the  nucleotides  of mrna three by three, in units called  codons  , and matches each to three nucleotides on the trna, called the anticodon. finally, during termination, the ribosome unbinds from the mrna, and the  amino acid  chain goes on to be processed and folded to make the final, functional protein