i) It provides traditional uses of plant.
ii) It gives information about certain unknown and known useful plants.
iii) The ethnomedicinal data will serve as a useful source of information for the chemists, pharmacologists and practitioners of herbal medicine.
iv) Tribal communities utilize ethnomedicinal plant parts like bark, stem, roots, leaves, flower bud, flowers, fruits, seeds, oils, resins, dyes, gum for the treatment of diseases like diarrhoea, fever, headache, diabetes, jaundice, snakebites, leprosy, etc.

i) Thiruvakkarai fossil wood park is located in Villupuram district of Tamil Nadu.
ii) The park contains petrified wood fossils.
iii) 20 million years ago tree trunks that got buried along the river, incourse of time the organic matter was replaced by silica and was fossilized.
iv) They retained their color, shape and texture and was converted into solid rocks.
v) The annular rings, the texture, colors of the layers, nodes and every properties of plants are still visible.

i) Internal vital force: Living organisms or their component parts tend to increase in size continuously. This increase in size is due to the inherent ability of the organisms.
ii) Environment and new needs: A change in the environment brings about changes in the need of the organisms. In response to the changing environment, the organisms develop certain adaptive characters. The adaptations of the organisms may be in the form of development of new parts of the body.
iii) Use and disuse theory: Lamarck’s use and disuse theory states that if an organ is used constantly, the organ develops well and gets strengthened. When an organ is not used for a long time, it gradually degenerates. The ancestors of giraffe were provided with short neck and short forelimbs. Due to shortage of grass, they were forced to feed on leaves from trees. The continuous stretching of their neck and forelimbs resulted in the development of long neck and long forelimbs which is an example for constant use of an organ. The degenerated wing of Kiwi is an example for organ of disuse.
iv) Theory of Inheritance of acquired characters: When there is a change in the environment, the animals respond to the change. They develop adaptive structures. The characters developed by the animals during their life time, in response to the environmental changes are called acquired characters. According to Lamarck, the acquired characters are transmitted to the offspring by the process of inheritance.

The comparative study of morphology and anatomy of animals, reveal that they possess common set of characteristics.
i) Homologous organs: The homologous organs are those which have inherited from common ancestors with similar developmental pattern in embryos. The fore limbs of mammals are homologous structures. A human hand, a front leg of a cat, flipper of a whale and a bat’s wing look dissimilar and adapted for different functions. Their mode of development and basic structure of bone are similar.
ii) Analogous organs: The analogous organs look similar and perform similar functions but they have different origin and developmental pattern. The function of the wings of a bat, the wings of a bird and wings of an insect are similar, but their basic structures are different.
iii) Vestigial organs: The degenerated and non-functional organs of animals are called vestigial organs. The same organs are found to be well-developed and functional, in some of the related forms. Some of the vestigial organs in man are vermiform appendix, nictitating membrane, caudal vertebra, coccyx etc.
iv) Atavism: The reappearance of ancestral characters in some individuals is called atavism. e.g. Presence of rudimentary tail in new born babies, presence of thick hair on the human body.

Many theories have been postulated to explain the origin of life. The views on the origin of life has been put forth as
i) Special creation : This idea embodies that life on Earth is a divine creation and also attributes to supernatural event at a particular time in the past. It also emphasizes that life has not changed ever since its origin.
ii) Spontaneous generation
a) Abiogenesis: According to this theory life originated spontaneously from lifeless matter. It was believed that fishes originated from mud, frogs from moist soil and insects from decaying matter.
b) Biogenesis: It was speculated by Louis Pasteur (1862) that life originates from pre-existing life. He showed that pre-sterilised flasks kept closed airtight, with killed yeast, did not give rise to any life form, while in another flask Kept open to air living organisms arose from killed yeast.
iii) Extraterresterial or Cosmic origin: Some scientists still believe that life came from outer space. This states that units of life called spores (Panspermia) were transferred to different planets including earth. This is still an idea of some astronomers.
iv) Chemical Evolution of Life: This idea was developed by Oparin (1922) and Haldane (1929). They proposed that with the conditions prevailing on earth, life arose by a series of sequential chemical reactions. The first form of life could have come from pre-existing non-living inorganic molecules which gave rise to formation of diverse organic molecules which are transformed into colloid system to produce life. The modern concept on chemical evolution regarding origin of life was accepted.