The four limitations are
1.It's often impossible to repeat trials on the same subjects.
2-Subjects may report an inaccurate medical history.
3-It can be difficult to control all possible variables.
4-It's impossible to come up with testable scientific questions for human subjects.
Research involving human beings is ultimately necessary for improvements in human health and welfare. Any results about healthy physiology, illness causes, treatment effectiveness, learning, or behavior must be verified by carefully controlled investigations involving human participants. Sadly, not all human research have been valid and beneficial. It is possible to harm people in the name of research. The most well-known instances happened in Nazi Germany. Investigations conducted after the war found several crimes, including experiments in which participants were submerged in extremely cold water to determine how long it would take them to pass away from hypothermia.
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Hyaluronic acid, <span>also called </span>hyaluronan.
A. endoskeleton
Endoskeleton is not a characteristic of Arthropods that has attributed to their diversity and success. Endoskeleton is defined as inner characteristics of the skeletal feature of an organisms such as bears, humans, fish and etc.
Exoskeleton on the other hand is the trait by which arthropods posses. It is skeletal feature that is described outside or is extrinsic, this is evident as crabs have their skeletons outside of their body.
Answer:
Horizontal gene transfer
Explanation:
Horizontal gene transfer or lateral gene transfer is when an organisms of different species can acquire a gene from a different one. This process is well understood in bacteria and is responsible for the appearence of antibiotic resistant bacteria. Bacteria can take DNA fragments through a process known as transformation, but this is less common in eukaryotes. Gene transfer agents like viruses could carry the gene from one specimen to the other. Another way could be Horizontal transposon transfer but the exact mechanisms behind it are still under research.
