<span>Anton van Leeuwenhoek learned to grind lenses ( 1668) and develop simple microscopes.
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Leeuwenhoek heated the middle of a small soda glass rod , over a flame. On pulling apart the two ends, the glass rod elongated into thin whiskers .
Heating the end of this whisker resulted in a tiny high quality glass sphere. These glass spheres then became the lens of his microscope, with the smallest sphere providing the greatest magnification.
Leeuwenhoek's designs were very basic. The body of the microscope was a single lens mounted in a tiny hole on a brass plate. The specimen was then mounted on a sharp point that sticks up in front of the lens. It's position and focus could be adjusted by turning the two screws.
The entire instrument was about 3 to 4 inches long and had to be held up close to the eye, requiring good lighting and great patience to use.
1. The cell wall has lignin (hard substance): to prevent the xylem vessel from collapsing and withstand high pressure.
2. The absence of protoplasm (nucleus + cytoplasm) and cross wall: to allow water to move through the lumen easily.
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Answer:
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Explanation:
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Answer:
B. Meiosis I
Explanation:
In meiosis I, it starts with a diploid cell with a homologous chromosome pair. The crossing of genetic material between chromosome pairs also occurs in this stage. The alleles containing the same trait would get separated so a new combination of alleles can be produced.
The major causes of the greenhouse effect is excessive carbon dioxide gas in the atmosphere. The greenhouse effect is a process that warms the Earth's surface. When the Sun's energy reaches the Earth's atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by green house gases, such as carbon dioxide, water vapor, metahne, nitrous oxide, and ozone. The absorbed energy warms the atmosphere and the surface of the Earth.
