Locomotion And Movement

Answer (a) Patella

Step 1: Understanding net productivity.
Net productivity refers to the amount of organic matter produced by plants that remains after respiration losses.

Step 2: Measurement units.
It is commonly measured in terms of biomass or carbon accumulated per unit area per unit time.

Step 3: Identifying the correct expression.
Production of carbon in g/m\textsuperscript{2}/day correctly represents net productivity.

Step 4: Conclusion.
Hence, net productivity is expressed as production of carbon per unit area per day.

The Hershey-Chase experiment, conducted in 1952, played a pivotal role in demonstrating that DNA, rather than protein, is the genetic material responsible for heredity. This experiment involved the use of bacteriophages—viruses that infect bacteria. At the time, there was ongoing debate about whether proteins or nucleic acids (DNA or RNA) were the key molecules carrying genetic information. Hershey and Chase's groundbreaking work helped resolve this question. Step 1: The Experimental Design.
To trace which component of the bacteriophage (either the protein or the DNA) entered the bacterial cell and carried the genetic information, Hershey and Chase used two different radioactive isotopes: (radioactive phosphorus) was used to label DNA, because phosphorus is an integral component of DNA but is absent in proteins. (radioactive sulfur) was used to label proteins, as sulfur is present in proteins but not in DNA. These labeled bacteriophages were then allowed to infect *Escherichia coli* (E. coli) bacteria, which served as the host. Step 2: Separation of Viral Components.
After allowing the bacteriophages to infect the bacteria, Hershey and Chase used a blender to separate the viral protein coats (which remained outside the bacterial cells) from the bacterial cells themselves. This mechanical agitation broke apart the bacteriophage coats from the bacterial cells. Then, they used centrifugation to separate the heavier bacterial cells, which contained the genetic material, from the lighter protein coats, which stayed in the liquid supernatant. Step 3: Key Observations and Conclusion.
The key results of the experiment were as follows: The radioactive phosphorus ( ) from the DNA was found inside the bacterial cells, indicating that the DNA from the bacteriophage had entered the bacteria during infection. The radioactive sulfur ( ) remained in the supernatant, indicating that the protein did not enter the bacterial cells. These findings conclusively showed that it was the DNA, not the protein, that carried the genetic instructions for the bacteriophage to reproduce within the bacterial host. Thus, the conclusion from the Hershey-Chase experiment was that