Q.23. Differentiate between fossil and living fossil. (2011)
Ans. Differences between fossil and living fossil
Q.24. What is the significance of fossil studies? (2010)
Ans. Significance of Fossil Studies: -
The study of fossils is of great significance in understanding the process of evolution. These have been described as the written documentary of the process of evolution contained in the rocks in the language of fossils.
The study of fossils, provides following clues:
1. Evidence in favour of organic evolution: - According to the theory of “Organic Evolution”, the more advanced forms of today has evolved from the simpler and more primitive ancestral forms living in the past. The fossils of the organisms in the older rocks are found to be more simple than those contained in the new rocks or those living today. The. fossils contained in the older rocks differ considerably from the living forms and those contained in the younger rocks appear to be more closely related to the present day forms. This succession of fossils clearly indicates that life has evolved gradually from simpler forms to more complex forms.
2. Fossils and the prehistorical life:- The fossils provide useful information about the animals and plant living in the past. The giant dinosaurs, ammonoites and trilobites are known from their fossils records only. Fossils have also helped in determining the relationship among different plant groups and the animals groups.
3. Pedigree of certain animal groups: - The evolutionary history of certain animal groups is so completely depicted by the fossil records that almost a complete unbroken sequence of different ancestral forms has been obtained. Pedigree of horse, elephant and camel can be quoted as examples of such fossil records.
4. Fossils and paleogeography: - With the help of fossil it is possible to reconstruct ancient geography of earth. By observing the nature of fossils in a particular earea, it is possible to depict the habitat of that area. For example, presence of fossil trees of stumps indicates the terrestrial environment. Similarly, the fossils of corals and ethinoderms, etc., are suggestive of marine environment.
5. Fossils as climatic indicators: - Fossils also help in determining the climatic conditions of the zoological period. For example, fossil ferns and associated plants such as Mangoliers suggest a warmer climatic condition. The glacial or colder conditional are indicated by the presence of such fossils as musk ox and reindeers.
Q.25. Describe Mesozoic period (2010, 12, 13)
Ans. Mesozoic Period: -
The Mesozoic era began about 230,000,000 years ago lasted some 167,000,000 years.
The atmosphere of this era was dry and hot. The Mesozoic era was the age of dinosaurs and gymnosperms. Towards the end of Mesozoic the flowering plant becomes dominant. This era has been divided into three periods-
1. Triassic Period: Triassic period began about 2.0 million years ago. In this period seed ferns had extinct and the gymnosperms such as conifers and cycads became predominant.
2. Jurassic Period: Jurassic period began about 180 million years ago. During this period the continents were moderately high and climate was becoming more wet. In this period new plants were spreading, with the deadline of older plants. Dicotyledonous plants were increasing.
3. Cretaceous Period: Cretaceous period began about 935 million years ago. During this period many inland seas arid swamps appeard in early time while in later time, mountain formation took place mainly the rocky, the Andes, the Alps and the Himalayas mountains. In this period, more modern plants were developing. The gymnosperms were declining with the establishment of oak and maple forests. Monocotyledonous plants appeared.