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.
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Organisms that originated in a certain geographic region and can only be found in that region are said to be endemic.
Explanation:
Endemic organisms are taxonomic species (plants and animals) which originates and distributed only in specific geographic regions. This state of evolution is called endemism.
They are said to be native or indigenous to that particular region which can be an ecological habitat, an entire nation, an island, a mountain range etc. Certain parts are known for majority of their species being endemic like St. Helen Island, New Caledonia Island, Hawaiian Islands, Southern regions of Africa, and Australia.
The species becomes endemic to a particular region because of the presence of certain bio-geographical environmental qualities of that habitat which are favorable to that species.
When these conditions become unfavorable, then species becomes restricted leading to endangerment or extinction of the species.
Examples:
- Kangaroo - Australia
- Nilgiri Tahr, - Nilgiri Hills, India
- The Redwood trees of West Coast of the USA
- Plants like kalo, sumac of Hawaii
I think it’s A. hope this helps