What does HIV stand for? Is AIDS an infectious disease? List any four modes of spreading AIDS.
Describe any three ways in which individuals with a particular trait may increase in population.
a) State two properties of carbon which lead to a very large number of carbon compounds.
b) Why does micelle formation take place when soap is added to water? why are micelles not formed when soap is added to ethanol ?
Or
Explain isomerism. State any four characteristics of isomers. Draw the structure of possible isomers of butane C4H10.
a) What is meant by the 'power of a lens'?
b) State and define the S.I. unit of power of a lens.
c) A convex lens of focal length 25 cm and a concave lens of focal length 10 cm are placed in close contact with each other.
Calculate the lens power of this combination.
What is binary fission in organisms? With the help of suitable diagrams, describe the mode of reproduction in Amoeba.
Binary fission which means division in half. It is a kind of asexual reproduction. It is the most common form of reproduction in prokaryotes and occurs in some single-celled eukaryotes. After replicating its genetic material, the cell divides into two nearly equal sized daughter cells.
In unicellular organisms like Amoeba cell division, or fission, leads to the creation of new individuals. The parent cell simply splita into two equal halves during cell division. In organisms such as Amoeba, the splitting of the two cells during division can take place in any plane.
It takes place in the following steps
i. Parent cell enlarges and the nucleus develops constriction.
ii. The cytoplasm divided with the two nucleus.
iii. The cell divides into two.