Short-Answer Questions.
1. Define cells and cell theory.
2. Define cell structure and name its various parts.
3. How do cells grow and divide?
4. How many cells are there in a human body? Name some of them.
5. Write a short note on discovery of the cell.
Answers
1.The cell theory states that all biological organisms are composed of cells; cells are the unit of life and all life come from preexisting life. The cell theory is so established today that it forms one of the unifying principles of biology.
The word cell was first used by Robert Hooke (1635–1703) when he looked at cork with a simple microscope and found what appeared to be blocks of material making up the cork. The term today describes a microscopic unit of life that separates itself from its surroundings by a thin partition, the cell membrane.
Most biologists believe that life arose spontaneously from inanimate matter, but the details of how this could have happened remain unknown, and the time scale was long. Rudolf Virchow, a German pathologist (1821–1902), famously wrote “omnis cellula e cellula”—all cells come from other cells—meaning that spontaneous generation of living things from inanimate matter does not occur over periods as short as our lifetimes.
2.There are many different types, sizes, and shapes of cells in the body. For descriptive purposes, the concept of a "generalized cell" is introduced. It includes features from all cell types. A cell consists of three parts: the cell membrane, the nucleus, and, between the two, the cytoplasm. Within the cytoplasm lie intricate arrangements of fine fibers and hundreds or even thousands of miniscule but distinct structures called organelles.
1)Cell membrane
2)Nucleus and Nucleolus
3)Cytoplasm
4)Cytoplasmic organelles(mitochondrion, ribosomes, endoplasmic reticulum, golgi apparatus, and lysosomes.)
3.The stages in a cell's life are called the cell cycle. This works a bit like a washing machine cycle - each stage must be finished completely before the next one is allowed to start. Instead of wash, rinse, spin and drain, the cell cycle is made up of stages in which the cell grows and rests, copies its DNA, and divides into two new cells.
4.Scientists concluded that the average human body contains approximately 37.2 trillion cells
Stem cells
Red blood cells
White blood cells
Platelets
Nerve cells
Muscle cells
Cartillage cells
Skin cells
Merkel cells
Langerhans cells
Endothelial
Epithelial cells
Fat cells
Sex cells
5.While the invention of the telescope made the Cosmos accessible to human observation, the microsope opened up smaller worlds, showing what living forms were composed of. The cell was first discovered and named by Robert Hooke in 1665. He remarked that it looked strangely similar to cellula or small rooms which monks inhabited, thus deriving the name. However what Hooke actually saw was the dead cell walls of plant cells (cork) as it appeared under the microscope. Hooke’s description of these cells was published in Micrographia. The cell walls observed by Hooke gave no indication of the nucleus and other organelles found in most living cells. The first man to witness a live cell under a microscope was Anton van Leeuwenhoek, who in 1674 described the algae Spirogyra. Van Leeuwenhoek probably also saw bacteria.
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Answer:
1)cell is a structural and functional unit of body of every organisms .cell theory says that it is indivisible and indistrictable.
2)parts of cell are called cell organelle which are embedded in cytoplasm with cell wall or cell membrane .
name of parts are cytoplasm , cell wall, cell membrane ,nucleus, ribosome, lysosome, mitocondria ,etc
3)cell divide by method of cell division which occur sexually or unsexually.
4)there are many cell in human body .for ex blood cells nerve cells
5)robert hooke discoverd cell by observing it under slides