Tag: natural selection

Evidence for evolution is gathered from multiple scientific fields. Paleontology provides fossil records, embryology shows developmental similarities, and anatomy (comparative anatomy) reveals homologous structures, all supporting the theory of evolution.

Evolution brings about several modifications to acclimatize with the changing environment. August Weismann (1834-1914) was a neo-Darwinian biologist who proposed the germplasm theory in his book Das Keimplasma. He said that variations are of two types. Some are congenital i.e., organisms are born with them. Others are acquired during the lifetime of a particular plant or animal. It was with this latter type of variations, the acquired characters, that Weismann was very much concerned. He gradually developed his 'Theory of Germplasm' to explain that acquired characters could not be inherited.

Evolution is the gradual change in the traits in order to adjust to the changing environmental conditions. Relative dating helps in evolution to detect the relative order of past events in comparison to other organisms. Similarly, carbon dating is used to know the age of the fossils on the basis of which evolutionary relationship is determined. It also helped to study the origin of life. So, the given statement is true.

• The Miller-Urey experiment was an experiment that simulated hypothetical conditions present on the early Earth in order to test what kind of environment would be needed to allow life to begin. The experiment is considered to be the classic experiment on the origin of life. 
• It was conducted in 1953 by Stanley L. Miller and Harold C. Urey at the University of Chicago. The experiment used water (H2O), methane (CH4), ammonia (NH3) and hydrogen (H2) - materials which were believed to represent the major components of the early Earth's atmosphere. The chemicals were all sealed and circulated inside a sterile array of glass tubes and flasks connected together in a loop, with one flask half-full of liquid water and another flask containing a pair of electrodes. 
• The liquid water was heated to add water vapor to the chemical mixture and the resulting gases were circulated around the apparatus, simulating the Earth's atmosphere. The flask with heated water represents water on the Earth's surface and the recycled water vapor is just as water evaporates from lakes and seas, before going into the atmosphere and forming into the rain. Sparks were fired between the electrodes to simulate lightning storms (believed to be common on the early earth) through the water vapors, and then the vapors were cooled again so that the water could condense (simulating the oceans) and trickle back into the first water flask in a continuous cycle. 
• At the end of one week of continuous operation, Miller and Urey observed, by analyzing the cooled water, that as much as 10-15% of the carbon within the system was now in the form of organic compounds. Two percent of the carbon had formed amino acids, including 13 of the 22 that are used to make proteins in living cells, with glycine as the most abundant. 

A- The Miller-Urey experiment or Miller experiment was an experiment that instigated the condition which were thought to be present in early earth or primitive earth. Hecreated electric discharge in a closed flask containing a mixture of ammonia(NH3), methane(CH4), hydrogen(H2) and water vapour(H2O) at 800 degree celcius and observed formation of amino acids The ratio of CH4,NH3 and H2 was 2:1:2.

Darwin and Lamarck are foundational figures in evolutionary theory. Hugo de Vries is known for his mutation theory, and Huxley was a major proponent of Darwinism.

Louis Pasteur conducted the famous swan neck flask experiments to disprove the theory of spontaneous generation. He demonstrated that microorganisms are present in the air and do not arise spontaneously.