34.

(a) Explain the evolution of the long neck of giraffe according to Darwin and Lamarck.

(b) Explain briefly :
(i) Environmental resistance
(ii) Albinism
(iii) Plant introduction
(iv) Palaeontology

(c) Write two uses of each of the following :
(i) Emblica officinalis
(ii) Adhatoda vasica

(a) In ancient times,the necks of giraffes were short. As the leaves on the lower branches of trees became scarce,the giraffe were forced to reach for the leaves on higher branches of trees. The animals with comparatively longer necks were certainly more fit because they could get leaves on higher branches which ensured their survival.But animals with short necks could not get those leaves so they had to die.Hence animals having longer necks were selected by the nature. Thus this practice carried over the generations and hence girafe got the longer necks. Accoring to Lamarck theory, this information of stretcheched neck carried over the generations and it was also transmitted to gametes making this feature permanent for giraffes.

(b) (i) Environmental resistance : It includes various environmental factors such as shortage of food , space, shelter and predation,etc. which do not permit survival of all the the members of a species. Increasing population requires more fuel, clothing, drinking water, houses, health facilities, etc. This puts pressure on natural resources and disturbs the planned utilisation of these resources..

(ii) Albinism : It is a form of hypo pigmentary congenital disorder, characterized by a lack of melanin pigment in eyes, skin and hair. It results from inheritance of recessive genes. The conditionis known to affect mammals, fish, birds, reptiles and amphibians.

(iii) Plant inroduction : It is the process of introducing a new plant into a new locality from its original place where climate is different. Their sucessful planting in new localty is termed as accimatization. The new crop varities can be in the form of seeds or cutting. It improves the crop yield for example cincona is introduced in peru and papaya is introduced from West Indies from India.

(d) Palentology : It is the study of fossils. It explains the existence of life in past and illustrates the course of evolutionof animals and plants.For example the fossil of Archaeopterysx lithographic is a connecting link between reptiles and birds.

c)

i. Embellica officinalis -

The fruits are a rich source of Vitamin C.
 
The fruits are used as a laxative. 

ii. Adhatoda vasica

Powdered leaves are useful in skin infection treatment.

The leaf juice is used in diarrhea,and glandular tumors.