31 Years NEET Previous Year Questions: Evolution - 4 - NEET MCQ

Adaptive radiation in evolution was developed by H.F. Osborn in 1898. It is also known as “Divergent evolution”. It is development of different functional structures from a common ancestral form. Examples as mentioned in the questions. Whereas development of similar adaptive functional structures in unrelated groups of organism is adaptive convergence = convergent evolution, e.g wings of insect, bird and bat. When convergent evolution is found in closely related species, it is called “Parallel Evolution” Example : development of running habit in deer (2.toed) and horse (1 toed). The evolutionary  process in which many related species evolved from a single ancestors is called adaptive radiation.

Adaptation is the evolutionary process in which population becomes better suited to its habitat. Mimicry is an example of long term adaptation, in which there is a close resemblance of an organism to the surrounding in order to avoid detection . e.g. Leaf insect Phyllium. The term mimicry was introduced by Bates (1862).
 • Homology is phenomenon in which origin of organs are same but functions are different. e.g - Hand of human and fore limb of horse.
• Analogy - Origin is different but functions are same of two different organs. e.g. - Wings of birds, wings of insects.

The term Evolution was given by Herbert Spencer that is “Descent with modifications”. Evolution helps us to understand the history of life.
Evolution is a process in which something changes into a different and usually more complete or better form over time and in response to environment. This results in descendents becoming different from ancestors.

August Weismann, tested Lamarck’s theory in 1904 by cutting off the tails of mice for 22 generations yet he failed to get tailless mouse. On the basis of the test he put forward the theory “continuity of germ plasm”. According to him the character influencing the germ cells (reproductive) are inherited. Change in somatic cells are not transmitted to the next generations. Hugo de Vries proposed “Mutation theory”.

One of the first attempts to explain the mechanism of evolution was made by Jean Baptiste de Lamarck. His theory was Inheritance of Acquired Characters. The theory states that the characters acquired during life time are passed on to the progeny and then to subsequent generations and new species are produced.

The book “Origin of species” was written by Darwin.

In convergent evolution similar adaptive functional structure develop in different species (unrelated group of organism). When convergent evolution is found in separate but closely related species (related evolutionary lineages) it is called parallel evolution.
In parallel evolution the two species have a relatively recent common ancestors.

Van Baer; 1828 put forward Baer’s law which was later called as Biogenetic law of Ernst Haeckel, 1866. The law states that "Ontogeny repeats phylogeny". Ontogeny is the life history of an organism while phylogeny is the evolutionary history of the race of that organism.

Oxygen gas was not present due to reducing atmosphere , it only came to existence after the evolution of photosynthesis process.

The correct Geological time scale of earth is Precambrian → Palaeozoic → (Era/Age of early life) Age of fishes Mesozoic → Coenozoic (Age of reptiles) (Age of mammals) dinasaurs and cycads A geological time scale is a diagram that details the history of Earths geology, noting major events like the formation of the Earth, the first life forms and mass extinctions. The first geological time scale was proposed in 1913 by the British geologist Arthur Holmes (1890-1965).
The history of the earth has been subdivided into eras, eras into periods and periods into major divisions.

Chemoheterotrophs were first organisms. They were prokaryotic like bacteria, anaerobes, as molecular oxygen was absent. They obtained energy by fermentation of some of the organic molecules present in the broth. Thus they absorbed organic molecules from outside for body building and energy.          
• Chemoautotrophs - Organisms that are capable to synthesize organic molecules from inorganic molecules.
E.g., Nitrifying bacteria, sulphur reducing bacteria etc.          
• Autotrophs are photosynthesizing     plants /organisms.

Evolutionary convergence is a type of evolutionary pattern in which unrelated organisms/different species develop common set of characters / adaptive functional structures (analogous structures). They do not share common ancestor, related to one another in only the most distant sense.

In 1859 Charles Darwin published his theory of natural selection in the book ‘Origin of Species’. The theory is based on five important observations :
1. All species have great reproductive potential
2. Most populations are stable in size
3. Natural resources are limited
4. Individuals of a population have variations.
5. Most of the variations are heritable.
Species with variations selected by nature.

Genetic  drift is also known as Sewall Wright effect. It refers to the random changes in gene frequencies in a population by chance, either due to intensive inbreeding or death of a small section of population by  natural calamity. Its effect is more marked in small isolated population.

Adaptable

Melanisation of Peppered Moth in industrial areas.

Loss of tail

Jurassic period of Mesozoic era is known as “Golden age of Dinosaurs.
• Coenozoic era is the age of insects, birds and mammals.
• Palaeozoic era of fishes.

Organs that are similar in fundamental structure but different in functions are “Homologous organs”, Richard Owen, introduced the term homologous. Pectoral fins of fish and fore limbs of horse similar in structure but different in functions are homologous organs.
Rest of the organs compared in the question are analogous organs

Evolutionary history of horse was described by O.C. Marsh, 1879. Origin of horse took place in Eocene period and first fossil of horse was Eohippus found in North America.

Dr. P. L. Sclater, 1858 divided the world into 6-regions on the basis of distribution of birds only, later in 1876 A.R. Wallace adopted it for all the animals. These six realms (regions) support evidence of organic evolution.

Recapitulation theory says that embryological development repeats path of evolution. Gill slits are present in the fishes and the aquatic amphibians and from them gradually the reptiles and mammals have evolved.

Homologous organs have same basic structure and origin but they differ in their external appearance and  function.

The sibling species are those species, which are born from a similar kind of parents having similar morphology. But they are reproductively isolated.