A biological system is a complex network of biologically relevant entities. ... Examples of biological systems at the macro scale are populations of organisms. On the organ and tissue scale in mammals and other animals, examples include the circulatory system, the respiratory system, and the nervous system. source: google
1.a
2.c
3.a
4.a
have a good day!!
<span>Animals and plants have cells that are specialized by the process of differentiation.</span>
Also viruses have nucleic acid whether DNA or RNA nucleic acid, they are so minute that you can't observed them,
it's letter C, they are also responsible for proteins. their cell wall is made up of capsid.
