SOME (VERY) IMPORTANT QUESTION FOR SCIENCE PART 2.. - Class 10 PDF Download

Q1)   Distinguish between esterification and saponification reactions with the help of the chemical equations for each. State one use of each (i) esters, and (ii) saponification process.

Answer :

Esterification is the process by which esters are formed when an alcohol reacts with an acid in presence of conc. Sulphuric acid.

R’OH RCOOH → RCOOR’ H2O

CH3CH2OH CH3COOH → CH3COOC2H5 H2O

Saponification reaction is when ester reacts with NaOH, to form sodium salt of acid and alcohol.

RCOOR’ NaOH → RCOONa R’OH

CH3COOC2H5 NaOH → CH3COONa C2H5OH

Esters are used in making perfumes, artificial flavouring agents, ice-creams, cold drinks.

Saponification process is used in making soaps.

Q2) How did Mendel explain that it is possible that a trait is inherited but not expressed in an organism?

Answer :

When Mendel crossed pure tall (TT) pea plants with a pure dwarf (tt) pea plants, in the F1 generation he found that all pea plants were tall (Tt). There were no dwarf plants produced in an F1 generation. When he self-pollinated these F1 plants, in the F2 generation he obtained tall and dwarf plants in the ratio 3:1. Thus as three-fourths of the plant in an F2 generation are tall and one-fourth is dwarf so tall is a dominant trait whereas dwarf is a recessive trait [ which expressed itself only in homozygous condition]. The dwarf trait was inherited in an F1 generation but it does not get expressed, it remains suppressed in presence of dominant trait tall.

Q3) ‘‘Evolution and classification of organisms are interlinked.’’ Give reasons to justify this statement.

Answer :

Classification refers to the arrangement of organisms into groups, sub-groups basing on their similarities and dissimilarities. The more similarities between the two organisms are placed in one group and dissimilar organisms are put in separate groups. The more similar characteristics of organisms found that means they are more closely related and might have a common ancestor. By identifying various characteristics, we can find out the evolutionary relationships among different organisms. Thus, classification of organisms reflects their evolutionary relationships.