Answer:
Genetic, geographic & cultural factors that cause sickle-cell anemia. It is important to note that even genetic diseases are caused by multiple social, environmental and biological factors. This is particularly true in the case of sickle-cell anemia, a genetically inherited blood disorder usually found in people with West African ancestry (PBS 2001).
<span>Grasslands are one of the most widespread of all the major vegetation types of the world. This is so, however, only because human manipulation of the land has significantly altered the natural vegetation, creating artificial grasslands of cereal crops, pastures, and other areas that require some form of repetitious, unnatural disturbance such as cultivation, heavy grazing, burning, or mowing to persist. This discussion, however, concentrates on natural and nearly natural grasslands.
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Explanation:
Organisms don’t have to only reproduce sexually or only reproduce asexually - some animals do both!
When conditions are good, such organisms will reproduce asexually because it is easier. For example, starfish (by fragmentation), slime molds, and water fleas/daphnia (by parthenogenesis) all reproduce asexually when there is plenty of food, minimal predators, and not too much crowding of individuals of the same species.
When conditions worsen (less food, too many individuals, etc), they may switch to sexual reproduction in order to add genetic variation to their population and ensure survival through difficult times.
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The theory of Continental Dift
Answer:
Listen to pronunciation. (al-VEE-oh-ly) Tiny air sacs at the end of the bronchioles (tiny branches of air tubes in the lungs). The alveoli are where the lungs and the blood exchange oxygen and carbon dioxide during the process of breathing in and breathing out.