It's something to do with the fact that having sickle cell anaemia reduces the chances of contracting malaria, obviously a very common disease in Africa. I'm not quite sure what the link is but hopefully this helps a little bit?
Answer: Atmospheric Nitrogen is unreactive
Explanation:
The atmosphere is made up of about 80% Nitrogen, 16% oxygen, about 4% carbon dioxide, rare gases etc.
However, the 80% Nitrogen is highly unreactive, and needs to be trapped by competent micro organisms known as nitrogen-fixing bacteria in the root nodules of legumes.
Then, it is converted to several forms like nitrites, nitrates (easily absorbed by plants), ammonia and finally escape to the atmosphere again.
This brief illustration explains the NITROGEN CYCLE, and it is the only means by which plants and animals can use the highly unreactive nitrogen
Answer:
The correct answer is - tend to lose water by osmosis since their internal salt concentration is lower than that of seawater.
Explanation:
In freshwater fishes, the body of fishes has a higher salt concentration inside their body than the surrounding water, water enters through the osmosis process. Without any active regulation of this process, fishes would swell and get bigger and bigger. They have specialized cells called chloride cells in gills to take ions from water as they do not have kidneys.
In contrast, the marine fishes have a lower salt concentration in their body than surrounding water of sea or ocean and they lose water continuously and to compensate for this they need to drink water regularly.
