In biology, cell theory is a scientific theory which describes the properties of cells.
These cells are the basic unit of structure in all organisms and also
the basic unit of reproduction. With continual improvements made to microscopes
over time, magnification technology advanced enough to discover cells
in the 17th century. This discovery is largely attributed to Robert Hooke, and began the scientific study of cells, also known as cell biology.
Over a century later, many debates about cells began amongst
scientists. Most of these debates involved the nature of cellular
regeneration, and the idea of cells as a fundamental unit of life. Cell
theory was eventually formulated in 1839. This is usually credited to Matthias Schleiden and Theodor Schwann. However, many other scientists like Rudolf Virchow
contributed to the theory. Cell theory has become the foundation of
biology and is the most widely accepted explanation of the function of
cells.
The three tenets to the cell theory are as described below:
<span><span>All living organisms are composed of one or more cells. (However,
this is considered a controversy because non-cellular life such as
viruses are disputed as a life form. See Non-cellular life.)</span>The cell is the basic unit of structure and organization in organisms.<span>Cells arise from pre-existing cells.</span></span>
Answer:
During the asexual reproduction, bacteria can divide simply by binary fission in which one bacteria first replicate its genetic material and the cell divide in two daughter cells which are identical to the parent cell.
Asexual reproduction does not allow genetic variation therefore to get genetic variation bacteria can use conjugation, transformation and transduction process.
In conjugation, bacteria gets extra genetic material from other bacteria through sex pills. In transduction the genetic material enters into the bacterial cell through the virus then bacteria incorporate this genetic material in its genome.
In transformation, bacteria takes up the extra genetic material from it's surrounding. Therefore conjugation, transduction, and transformation helps bacterial to gain variation like as in sexual reproduction.
Answer:
The correct option is - (a) the activation and inactivation gates must both be open.
Explanation:
Option (a) is correct because of the following reason -
The axonal membrane is at its natural resting potential until an action potential occurs, and channels are deactivated and blocked on the extracellular side by their activation gates. The activation gates open in response to an electric current, allowing positively charged ions to flow into the neuron through the channels. When enough has penetrated the neuron and the membrane potential has reached a certain level, the channels inactivate themselves by closing their inactivation gates at the height of the action potential. The inactivation gate can be thought of as a "plug" tethered to the intracellular alpha subunit's domains III and IV. When the inactivation gate is closed, the flow of through the channel is stopped. As a result, both the activation and inactivation gates must be open to enable sodium ions to enter the cell.
<u>Hence , the correct option is (a).</u>
<h2>Answer is option " 2 & 4"</h2>
Explanation:
- Two types of posterity can be created subsequent to mating: parental and recombinant. Recombinants are created because of the traverse of non-sister chromatids at the hour of gamete arrangement. Here, mating happens between m+g/mg+ female and mg/mg male so the posterity would be separated as follows:
- m+g/mg : Parental
- mg+/mg : Parental
- m+g+/mg : Recombinant
- mg/mg : Recombinant
- m+g+/mg (wild sort) and mg/mg (smaller than usual wings, garnet eyes) are the recombinants thus they were created because of the hybrid occasion.
- Hence,the right answer is option 2 & 4 "wild type and miniature wings,garnet eyes"