(a) The laws of Mendel are in two parts: (i) Mendel's first law of segregation of genes states that genes are responsible for the development of the individual and that they are independently transmitted from one generation to another without undergoing any alteration.
(ii) Mendel's second law of independent assortment of genes states that each character behaves as a separate unit and is inherited independently of any other character.
(b)(i) Three advantages of introduction in crop improvement are (i) it helps to introduce new varieties of crops to the new area. (ii) It may enhance greater productivity. (iii) It may perform better if conducive climatic conditions are present in the new area.
(ii) Two disadvantages of introduction in crop improvement are (i) It may introduce new diseases to the new area. (ii) The new plants may not adapt to the new area. (iii)
Three advantages of selection in crop improvement are: (i) It reduces the spread of .ests and diseases. (ii) It ensures that only the best naturally available crop is grown. (iii) Crops with desired qualitities are selected .
While two of the disadvantages of selection in crop improvement are: (i) It is tedious and time (ii) requires expertise which may not be easily available.