Virus’s are not considered living organisms because:
1. they cannot reproduce by themselves.
2. are structurally very simple.
3. can only be visualized using an electron microscope.
4. typically are associated with diseases.
If an animal is having a well developed skeleton system, a backbone then it belongs to vertebrate. Also, size is an important factor to identify vertebrate and invertebrate.
Explanation:
Vertebrates have a well developed skeleton system and backbone. Their skeleton system is made up of bones and cartilage. While, invertebrates don't have any backbone.
Due to lack of backbone or skeleton system, invertebrates are small in size. As there is no proper mechanism to support large body so invertebrates are small in size and also they move very slowly. This is also a major difference in vertebrate and invertebrate.
Another important difference between vertebrate and invertebrate is that body of vertebrate is covered with some structure like hair, feathers, skin, scales or a combination of these.
These features help to distinguish vertebrate from invertebrate by observing them, no need to dissect.
C.striated Cardiac muscles are striated (have striations or lines) which is almost similar to that of skeletal muscles. The cardiac muscles also have many nuclei that act as one single unit
Not necessarily. I have no background on this kind of thing. I would say that they do not only for the facts of 1, where would they get a new heart? 2, I was born with three holes in my heart (I swear to God) and merely got patches. 3, Replacing the heart would be hard so as though when your heart stops beating you die. There would be only a very small space of time that would have to do so.
