Robert Hooke is the first person to observe cells as microscopic structures.
He was of British descent and, fun fact, he discovered cells by looking at a sliver of cork under a microscope lens (although the 'fun fact' is heavily simplified).
Ans.
Sickle-cell disorder shows defected red blood cells, due to mutation in gene that code for hemoglobin. The mutated genes for sickle-cell disease are found in higher percentage of sub-Saharan African population as it provides protection against malaria as compared to population of United States.
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.
Thus, the evolutionary process behind this is 'natural selection.'
Answer: G
Explanation: A galaxy is indeed a collection of stars, gas, and dust held together by gravity.
Answer:
The heart pumps blood through the circulatory system, delivering needed materials (glucose, oxygen) and picking up waste (carbon dioxide) from cells all over the body. Organs systems work together to efficiently and effectively provide all body cells with their basic needs to carry out life functions.
