Exoskeleton
Exoskeleton is a evolutionary innovation. This is operated by muscles attached to it and acts as an armor. Other than support this is an adaptive mechanism to provide protection against predators. In vertebrates, it is considered as the dermal bone that developed via membranous ossification. Fishes retained their exoskeleton in the form of their scales. However, in some organisms terrestrial evolution allows the loss of exoskeleton and formed a more mobile endoskeleton,
Most likely true because for all living things, their DNA is constantly mutating to keep itself alive in a certain environment,
Um your question is very unclear lol
This particular area of genetics can be quite complex. So basically in DNA their is adenine, cytosine, guanine, thymine. So, then there is another step to this: Adenine links with Thymine (A is to T), and Cytosine pairs up with Guanine (C is to G). This is known as base pairing. However, when translating DNA to RNA their is a catch, there is no thymine in RNA. Instead there is Uracil. SO in RNA it would be like so: A is to U and C is to G. So when transcribing DNA to mRNA it would be like this. I will give an example: DNA: TGA GTC AAT GGC. However with RNA it would be like this, using the same example I just showed you: ACU CAG UUA CCG. Do you see I it now? Basically when transcribing to RNA you use the opposite of all of the original copy except use Uracil instead of Thmine.
The different barriers that you have to go through are the different organs of the immune system. These are the lymphoid organs, thymus, and bone marrow. The secondary wall that you have to go through are the lymphatic tissues which include the lymph nodes, adenoids, skin, liver, tonsils, spleen, and the lymph vessels.
At all times, these systems work hand-in-hand so that the body can protect itself in order for it to survive
