Individuals who are heterozygous for the sickle-cell allele suffer less from the attack of malaria because a small percentage of the red blood cells are sickle-shaped. They are more resistant to malaria than individuals who have two copies of the normal haemoglobin allele. Heterozygous individuals have a better chance of surviving and reproducing in regions where malaria is prevalent since they do not fully contract the disease.
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Topographic maps and satellite images
Explanation:
A topographic map represents earth's surface features like land forms and structures, rivers and lakes, mountains and hills, elevations and other natural features along with man-made artificial features like cities, buildings, monuments, roads, bridges etc. These are formed by contour lines.
Topographic maps are printed with revision dates to observe the changes happening on the Earth's surface. Various land forms keeps changing due to natural and man-made causes and these needs to be updated accordingly to provide accurate details.
A satellite image provides details of the earth aerially from space. These provides details of a land form or any earth structure currently.
By comparing with older satellite images or topographic maps with the current one, the changes which occurred over time can be observed.
