31 Years NEET Previous Year Questions: Evolution - 3

Progressive evolution is development of organisms with more elaborate and specialized structures from those having less elaborate features e.g. amphibians from reptiles .Retrogressive or degenerative evolution is development of simpler forms from more complex ones. Such evolution has occurred in case of vestigial organs, parasitic forms,  and in reduction of overspecialized  structures such as wings in flightless birds. Parallel evolution is formation of similar traits in related groups of organisms independently due to similar requirement e.g. running of two toed deer and one toed Horse. Evolution of wings in insects and birds serve as example of convergent evolution

Elements present on the surface of the earth as well as in the early atmosphere combined to produce simple and compound molecules. Atmospheric elements  produced molecules of   Hydrogen, Nitrogen, Water, CO, CO₂, Ammonia, methane etc. UV-radiations, cosmic rays, lightening and heat made these to react amongst themselves and produce organ compounds like sugars, fatty acid, glycerol and amino acids.

Vestigial  organs are those organs which are non-functional in the possessor but were functional in their ancestors and in related animals. Human beings possess many vestigial organs like nictitating  membrane in the eye, vermiform appendix at the end of caecum, coccyx and tail muscles, non-functional muscles of the pinna, wisdom teeth, segmental muscle of abdomen and nipples in males.

This is known as Allen's rule.

Change of diet from fruits, hard nuts and roots to softer food encouraged settled human life.

Australopithecus appeared in early Pleistocene. Homo habilis had a cranial capacity of  700–800 cc. 

Cranial capacity shows an increase form apes to man which indicates increase in intelligence.

Homo erectus was a large hominid. It had a length of about 150 to 170 cm (5 to 5.5 feet) with a low but distinct forehead strong browridge and a brain capacity of about 1000 cc. Homo erectus was social and living in tribes of 20 to 50 people and thus had a successful and complex culture. It became widespread throughout the tropical and temperate old world.

Homologous organs are theorgans having  similar structural plan and origin but performing different functions. Analogous organs perform similar function but have different structural  and developmental origin e.g. wings of birds, wings of bat and wings of insects are analogous organs.

Hardy - Weinberg law is the principle of genetic equilibrium according to which in the absence of external environmental  disturbances, a randomly mating  population remains in genetic equilibrium. Lamarck postulated the theory of inheritance of acquired characters. Mendelian principles explained the inheritance of genetic characters from one generation to another.

Genetic drift can operate only on smaller populations where its fluctuation can be observed in the proportion of allele distribution in the presence of external disturbances. Genetic  drift is the random change in allele number and frequency in a gene pool.

Dryopiihecus lived about 20-25 million years ago. Dryopithecus had the combined characters of great apes, old world monkeys and maa. The main structuracharacteristics of Dryopithecus are broad jaws, large canines, semi-erect walking, 5 cusped molars and absence of brow ridges.

Synthesis of organic molecules from simple molecules is no longer possible because of the oxidizing atmosphere.

Nature select those set of characters that are best adapted to the environment. This has resulted in the great diversity seen in the population of finches.

Cro-Magnon  fossils have been found in Europe. Neanderthal man is  a transitional stage. Australopithecus appeared in early Pleistocene.

Human body contains about 180 vestigial organs coccyx, third molars (wisdom teeth) and muscles of abdomen etc.

Homeotic genes are the group of genes involved in the embryonic development and control the pattern of body formation. Alleination in these gene found in flies like  Drosophila result in development of legs in place of wings.

Oligocene is  masked by the rise of monkeys and apes. Miocene is masked by appearance of man like apes. Pliocene is characterized by origin of man.

Chimpanzees and gorillas are our closest relatives among the living primates

Loss of a prehensile tail is associated with the gradual development of errect posture and bipedal gait.

Biogeography is the study of geographical distribution of organisms. Paleontology is the study of past life  based on fossils and fossil impressions. Anatomy is the study of internal structure. Embryology is the study of development of embryo from zygote till it becomes an offspring.

Microevolution is a series of changes within a species due to gene mutations and accumulation of variations.
Macroevolution  is evolution in which taxa higher than  the level of species are formed due to morphological and cytological changes. Formation of different functional forms of a basically similar structure is called divergent evolution.

Chimpanzee is the closest relative of man. Banding pattern of human chromosome number 3 and 6 are remarkably similar to that of chimpanzee indicating common origin for both.

Peking man had a cranial capacity of about 1000cc. Heidelberg man is regarded as ancestor of Neanderthal man. Cro-Magnon is the form of modern man living in Europe.

According to both the views, 'something' is passed from parent to offspring which causes development of specific characters.