Tag: cell and its discovery

A. Histology is the branch of biology that deals with the study of animal and plant tissues.

• A microscope is an instrument, which is used for observing very small objects. 
• It uses lens or combination of lenses to produce a magnified image of tiny objects, which are not visible to the naked eyes. 
• Cells are also very small, which cannot be seen by the naked eyes. Hence, a microscope is used to observe cells. So option B is correct.

The deposition of callus occurs around the Microspore Mother Cell (MMC) prior to the cell undergoing meiotic division. The division results in the formation of a cluster of 4 haploid cells the microspores. These cells are held together by the callose to form a microspore tetrad. The callose deposition allows the development of the microspores into pollen grains by preventing them from sticking to each other. After complete development of the pollen the callose wall is disintegrated.

• Robert Brown discovered the nucleus of the cell. Robert Hooke discovered the cell. 

Most of the "animalcules" are now referred to as unicellular organisms, although Leeuwenhoek observed multicellular organisms in pond water. He was also the first to document microscopic observations of muscle fibers, bacteria, spermatozoa, red blood cells, crystals in gouty tophi, and blood flow in capillaries.

Frits Zernike invented phase contrast microscopy which was proved to be an advancement in microscopy. He was awarded Nobel prize in Physics in 1953.
Phase contrast microscopy is a optical microscopy technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image.

Scanning electron microscopes do provide 3D images but not naturally. However, 3D images can be obtained by different methods such as:
Photogrammetry where 2 or 3 images are there from tilted specimen.
Photometric stereo where there is use of 4 images from detector.

Fluorescence is the emission of light by a substance that has absorbed light. Here, the emitted light has a longer wavelength and, therefore, lower energy than the absorbed radiation.