Question

Schleiden and Schwann proposed ……………...

Answer 1

Hint: Cell theory was formulated and later modified by three scientists. This theory mentions cell structure, origin, and functions. The modern cell theory is known as the cell principle or cell doctrine.

Complete answer:
-The cell theory was proposed by Schleiden and Schwann.
-Both the scientists worked independently but together formulated the theory.
-Their cell theory mentioned the function and composition of cells but did not explain how new cells are formed.
-Cell theory was first modified in the light of Virchow’s findings that all cells arise from pre-existing cells,”Omnis cellulae cellula “.It is known as the law of cell lineage.
-M.J Schleiden, a German botanist in 1838 stated that ”All plants are formed of one or more cells.”
-Theodore Schwann, a German zoologist in 1839 stated that “All animals are formed of cells, have nuclei enclosed by thin cell membrane instead of the thick cell wall as found in plant cells.”
-According to the hypothesis proposed by Schwann, the bodies of plants and animals are composed of cells and their products.

Additional information:
-Mycoplasma are the smallest cells.
-An ostrich’s egg is the largest isolated single cell.
-Extensive compartmentalization of cytoplasm and the presence of membrane-bound cell organelles are the features of eukaryotes.
-Nerve cells are the longest cell.
-Cells acquire different shapes depending upon the function they perform.
-First live cell was discovered by Anton van Leeuwenhoek.

So, the correct answer is ‘Cell theory’.

Note:
There are many drawbacks to the cell theory. Viruses cannot be explained using this theory, Rhizopus have the multinucleated mass of cytoplasm, sieve tube and mature RBC lack nuclei, and so on. However, it is the most widely accepted theory.