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12th Biology 2011 Set1 Delhi Board Paper Solution

Question 29

Explain the salient features of Hugo de Vries theory of mutation. How is DarwinÂ’s theory of natural selection different from it? Explain.
(a) Name the primates that lived about 15 million years ago. List their characteristic features.
1. Where was the first man-like animal found?
2. Write the order in which Neanderthals, Homo habilis and Homo erectus appeared on earth. State the brain capacity of each one of them.
3. When did modern Homo sapiens appear on this planet?

Hugo de Vries by his experiment suggest that variation is caused due to mutation among the genetic sequence of an individual. Hugo de Vries for the first time gave the term saltation which stands for huge mutation in a single step resulting in speciation.
Darwin during his voyage in H.M.S Beagle he found that living organism share similar features existed from millions of years.
Evolution is a sequential process that leads to betterment of life forms to cope with the change in environment and that is passed into successive generation, called as natural selection. Mutation is a random process and direction of which is not specific.


(a) Evolution is a sequential process which takes millions of year to complete. About 15 million years ago (15 mya), the existing primates were Dryopithecus and Ramapithecus.
Characteristic features about Dryopithecus and Ramapithecus
1.Their body was covered with hair and there walking style resembled chimpanzee and gorillas.
2.Ramapithecus was more like a man then like and ape, while Dryopithecus was ape like.
(b) 1. Early evolution suggests Dryopithecus and Ramapithecus resembled with mammal feature. Presence of body hairs and walking style connect human to primate like gorillas and chimpanzees. 
2. Order of appearance on earth - Homo habilis, Homo erectus, Neanderthal man
i. Homo habilis- has the capacity of 650- 800cc, and they even didn’t eat meat.
ii. Homo erectus – has large brain size approx. 900cc and was probably non-vegetarian.
iii. Neanderthal man- has the largest size of brain with size of 1400 cc found in eastern Asia.
3. Development of Homo sapiens started in Africa while they moved across the world and gets differentiated into distinct races. Rise of modern Homo sapiens started after the Ice age which took place in between 75,000-10,000 years ago. After which cave art, agriculture forming basis of modern homo sapiens.