Ans.
Sickle-cell disorder is a genetic disorder, which shows defected red blood cells, due to mutation in the genes for hemoglobin protein.
Malaria is common in sub-Saharan Africa region and there, natural selection favored gene for sickle cells, because it might be beneficial to people having sickle cell disease that makes them able to survive in such condition and transmit their genes to offspring.
On the other hand, in those Africans, who moved to United States, where malaria is uncommon or absent, natural selection favored normal, wild type genes, resulting in fewer people with defected sickle cell.
Hence, sub-Saharan African population shows higher percentage of mutated gene for sickle cell as compared to population of United States.
Thus, the evolutionary process behind this difference is 'natural selection.'
The answer is B
A worker bee defends the hive while the queen be lay eggs like a good soldier would do
Desert vegetation or xerophytes includes bushes with deep roots and plants that store water.
Another name for desert plant:
A plant species known as a xerophyte has evolved to live in environments with little fluid water, like a desert or an area surrounded by ice or frost in the Mountains or the Polar regions. Cacti, pineapples, and various Gymnosperm species are a few well-known instances of xerophytes.
- Xerophytes have different adaptations to their morphological characters (morphology) and basic physiological functions (physiology) that allow them to store significant amounts of water and save it during dry seasons. During prolonged periods of severe dehydration or evaporation of their organs, some creatures can live, and at those times, their biochemical function may cease. Xeromorphic flora has such biological and morphological modifications.
Learn more about xerophyte here:
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Temperature difference and Earth's tilt