1). secondary; physical and thermal and radiological
2). primary; chemical radiological
3). secondary; physical and biological
If you are referring to bacteria, and other possible microorganisms, they are found everywhere whether that be the air surrounding us, to abiotic, non living components of the environment, such as water, soil, etc. Generally though, one celled organisms are found in soil. Substantially, it has been noted that a single hand full of soil, contains more microbes than the people in a given country etc.
The Cross-Linkage Theory or also referred to as the glycosylation theory of aging was discovered or proposed by Johan Bjorksten in the 1940s. According to this theory, the aggregation of cross-linked proteins can damage cells and tissues this slowing down the bodily processes that eventually results to aging. In recent studies, cross-linking is associated with age-related changes in the studied proteins. Furthermore, this theory stresses out that the binding of glucose to proteins can cause various problems. Once the said binding occurs, the protein becomes impaired which leads to its performance inefficiency. Living a longer life would also mean increasing the possibility of oxygen-glucose meeting and protein. Some of the known cross-linking disorders include senile cataract and the appearance of tough, leathery, yellow skin.
The answer is : linea aspera
