Tag: biology

According to the cell theory all organisms (unicellular or multicellular) are formed of cells. It also states that all cells arise from pre-existing cells by cell division and do not originate spontaneously. Bacteria and other organisms therefore cannot arise spontaneously. So, the correct answer is 'It states that bacteria and other small organisms can arise spontaneously'.

• Reproduction is based on the phenomenon that new cells arise from preexisting cells. 
• Spontaneous generation is not possible.

The evolution of the DNA to RNA to protein system allowed for the storage and replication of genetic information, which is essential for biological inheritance and the continuity of life.

Cell theory is the idea that the cell is the fundamental structural and functional unit of all living organisms and that new cells are formed from other existing cells. This theory is one of the foundations of modern biology. First formulated in the early 1800s in landmark publications by Mathias Jacob Schleiden and Theodor Schwann, the foundations of this theory began in mid-1600s through advances in microscopy. Today, it is held that all organisms are composed of one or more cells, all vital functions of an organism occur within cells, and cells contain the hereditary information necessary for regulating cell functions and for transmitting information to the next generation of cells.

Rudolf Virchow modified the cell theory and gave the concept of 'Omnis cellule e cellulae'- which means new cells develop by the division of the pre-existing cells. This is called the theory of cell lineage or common ancestry.

Antonie Philips van Leeuwenhoek was first to observe the living cell. He is commonly known as "the Father of Microbiology", and considered to be the first microbiologist. He is best known for his work on the improvement of the microscope and for his contributions towards the establishment of microbiology.
The cell was first discovered by Robert Hooke in 1665, which can be found to be described in his book Micrographia. In this book, he gave 60 observations in detail of various objects under a coarse, compound microscope. One observation was from very thin slices of bottle cork. Hooke discovered a multitude of tiny pores that he named "cells". 
Cell theory was eventually formulated in 1838. This is usually credited to Matthias Schleiden and Theodor Schwann.  Cell theory has become the foundation of biology and is the most widely accepted explanation of the function of cells.
Virchow is credited with many important discoveries. His most widely known scientific contribution is his cell theory, which built on the work of Theodor Schwann. He was one of the first to accept the work of Robert Remak, who showed the origins of cells was the division of pre-existing cells.

Lactobacillus converts milk into curd. It acts on the lactose of the milk and turns it into lactic acid. The increased acidity leads to the coagulation of casein protein of the milk and turns it into curd.

Statement (i) is incorrect because antibiotics are chemical substances produced by microorganisms (or synthetic versions) that kill or inhibit other microorganisms; they are not the attenuated microorganisms themselves (which describes vaccines).