Theory of natural selection - class-XI

Ernest Haeckel is the scientist who had contributed much to genetic evolutionary studies. He is the one who described: "Ontogeny recapitulates phylogeny".

Species dominance refers to the condition where one or a few species are found in much greater abundance than others in a community. Species richness refers to the total number of species, while species evenness refers to the relative abundance of different species.

Organic compounds essential for life can be produced by simple inorganic constituents that were the conclusion first derived by Miller and Urey on the basis of their experiment. They took the gases thought to be present in the primitive atmosphere in a sealed flask and exposed them to electric spark. Later on analysis of flask, many organic compounds could be recovered.

The first organisms that appeared on earth resembled single-celled life forms called archaea that can live in extreme environments such as hot springs and deep-sea vents. They were prokaryotic heterotrophs and used inorganic chemicals from the environment for carbon fixation and this process is called chemoautotrophy. They were anaerobic in nature because free oxygen was absent during primitive environment on earth.

The earliest living organisms were prokaryotes which later on evolved to give rise to eukaryotes and photosynthesizing organisms.

• The giant nucleoprotein molecules were formed by the union of nucleic acid and protein molecules. These nucleoprotein particles were described as free-living genes. Nucleoproteins gave most probably the first sign of life.
• Hence Nucleoprotein gave most probably the first sign of life.
• So, the correct answer is 'Life'.

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.

Moeritherium is extinct mammals. They are one of the first group of mammals that were present in the prehistoric era. They are also said to be distant relatives of modern-day elephants. Some of their features show remarkable similarities to modern-day elephants. So, they are said to direct evidence of the evolution of modern elephants and animals, 

The chemical evolution theory, or Oparin-Haldane hypothesis, proposes that life originated from non-living chemical substances through a series of reactions in the early Earth's atmosphere. This is the widely accepted scientific explanation for the origin of life.

• In biology, an atavism is a modification of a biological structure whereby an ancestral trait reappears after having been lost through the evolutionary change in previous generations. For example, the Appearance of ancestral characters in the new borne, such as the tail, multiple mammae, etc in humans, Extra toes of the modern horse, Reappearance of prothoracic wings in insects, etc.
• Hence Appearance of ancestral characters in the new borne, such as the tail, multiple mammae, etc., are known as an atavism.
• So, the correct answer is 'Atavism'.

• There are different reasons for the origin of s=new species from older ones. 
• One of these reasons is the development of random and sudden mutations. Mutations are nothing but changes that occur in DNA sequences. Certain environmental factors cause mutations. Thus, change in DNA sequence leads to the generation of a species with some altered character.
• Continental drift describes the relative change in geographical locations of the continents. This theory was first established by Abraham Ortelius saying that there must have been drift in the location of continents. This theory also explains the reason behind similar-looking animals on different continents.
• Natural calamities like earthquakes, tornadoes, volcanoes, hurricanes, etc cause large scale destruction of life and biodiversity. They also lead to the development of some characters in living organisms that are altered or modified forms of their original character. 
• So, they too lead to change inn current species character and form new species.
• So, all the given options are correct.

The dorsal nerve cord is a characteristic of chordates, but the presence of such a structure in both crayfish (an invertebrate) and birds (a vertebrate) is not a homologous trait used as evidence for evolution. The other options describe legitimate evidence like structural homology, molecular data, and fossil records.

In Industrial melanism, refers to the evolution of dark body colors in animal species that live in habitats blackened by industrial soot. The phenomenon has been documented in numerous species that hide from predators by blending in with their backgrounds. Birds play an important factor in natural selection.

Comparative cytology is the field of study involving looking at similarities in different organism's cells. 

Organic evolution is the process by which changes in the genetic composition of populations of organisms occur in response to environmental changes.

Genetic drift is a random process that changes allele frequencies in a population due to chance events, independent of the fitness of the individuals. Natural selection, conversely, is driven by the differential survival and reproduction of individuals based on their traits, which inherently involves competition.

Ernst Haeckel formulated his theory as "Ontogeny recapitulates phylogeny". “Ontogeny recapitulates phylogeny” was a commonly used phrase to explain the evidence supporting evolution. Ontogeny is “the complete developmental history of the individual organism,” and phylogeny is defined as “the complete evolutionary history of a group of organisms,”. Thus, this phrase means that the evolutionary history of a group of organisms is repeated during the developmental history of an individual organism of that group. This idea is also known as recapitulation. 

The primitive atmosphere of earth was reducing atmosphere with no oxygen but was rich in water vapour, carbon monoxide, carbon dioxide, nitrogen and hydrogen. Owing to immense long lasting rainstorms, a tremendous amount of lightening was generated. Lightening provided energy for chemical reactions between hydrogen and nitrogen and carbon to form ammonia and methane. So, the correct answer is option A.  

An imperative proof for natural advancement is the event of homologous and minimal organs. Homologous organs are those which have the regular inception and are based on a similar central example yet they perform diverse capacities and have distinctive appearances, e.g. whale's flipper, bat's wings, feline's paws, steed's front legs, fledgeling's wings, bull's front legs, and human hands.

Microevolution is the change in allele frequencies that occurs over time within a population. This change is due to four different processes: mutation, selection (natural and artificial), gene flow and genetic drift. As the natural selection a process in which organisms with certain inherited traits are more likely to survive and reproduce than are individuals with other traits. So natural selection is a differential reproductive success as it acquires useful

Nucleic acids were formed in a primitive hot soup of sea by the formation of pyrimidine-sugar –phosphate and purine-sugar-phosphate. RNA has the ability of self replication and to catalyze other chemical reactions. Thus, RNA served as an enzyme as well as genetic material in first life forms. Amino acids were formed by condensation, polymerization and redox reactions of hydrocarbons, ammonia and water in Primitive Ocean under influence of energy from UV rays, radiations and lightening. RNA catalyzed polymerization of these amino acids formed polypeptides. The nucleic acid came before proteins. Urea was synthesized as excretory material much later during the evolution of land animals as ammonia is very toxic and requires more water to serve as excretory material. Thus, the correct answer is option B.

In the evolutionary timeline of plants, Zosterophyllum is considered to have evolved from early tracheophyte ancestors, representing a primitive vascular plant lineage.

Character displacement is the term used to describe an evolutionary change that occurs when two similar species inhabit the same environment. This due to the geographical isolation.