1. Complete the following diagram. (March’19)
Ans. 
2. Read the following statements and justify same in your own words with the help of suitable examples.
a. Human evolution began approximately 7 crore years ago.
Ans.
(1) Last dinosaurs disappeared approximately seven crore years ago. (2) At that time, monkey like animals were said to be evolved from some ancestors who were more or less similar to the modem lemurs. (3) Thus, human evolution began approximately seven crore years ago.
b. Geographical and reproductive isolation of organisms gradually leads to speciation.
Ans.
(1) Species is the group of organisms that can produce fertile individuals through natural reproduction. (2) Each species grows in specific geographical condition. Their food, habitat, reproductive ability and period is different. (3) Along with genetic variation, geographical and reproductive changes are responsible for formation of new species. (4) Hence, geographical and reproductive isolation leads to speciation.
c. Study of fossils is an important aspect of study of evolution.
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(1) Large number of organisms get buried due to disasters like flood, earthquake, volcano, etc. (2) Remnants and impressions of such organisms remain preserved underground. These are called as fossils. (3) Study of fossils is an important aspect of study of evolution. (4) Carbon dating method is used in paleontology and anthropology for determining the age of human fossils and manuscripts. (5) Once the age of fossil been determined by such technique, it becomes easy to deduce the information about other erstwhile organisms. (6) It seems that vertebrates have been slowly originated from invertebrates.
d. There is evidences of fatal science among chordates.
Ans.
(1) Comparative study of embryonic developmental stages of various vertebrates like fish, salamander, tortoise, chicken pig, cow, rabbit and man shows that all embryos show extreme similarities during initial stages and those similarities decrease gradually. (2) The similarity of early embryonic development indicate that the above animals have common ancestors.
3. Complete the statements by choosing correct options from bracket.
(Gene, Mutation, Translocation, Transcription, Gradual development, Appendix)
c. Transfer of information from molecule of DNA to mRNA is called as ………… process. (March ’20)
Ans. Transfer of information from molecule of DNA to RNA is called as transcription process.
d. Evolution means …………..
Ans. Evolution means gradual development.
e. Vestigial organ ………….. present in human body is proof of evolution.
Ans. Vestigial organ Appendix present in human body is proof of evolution.
4. Write short notes based upon the information known to you.
a. Lamarckism
Ans. (1) Jean-Baptiste Lamarck proposed that morphological changes occurring in living organisms are responsible for evolution and the reason behind those morphological changes is activities or laziness of that organism. (2) He called this concept as principle of ‘use or disuse of organs’. (3) The living organism can transfer the characters which it has acquired, to the next generation. This is called ancestry of acquired characters. (4) Examples:- (a) The neck of giraffe has become too long due to browsing on leaves of tall plants by extending their neck for several generations. (b) Shoulders of the iron-smith have become very strong due to frequent hammering movements. (c) Wings of birds like ostrich and emu have become weak due to no use. (5) All these examples are types of ‘acquired characters’ and are transferred from one to another generation. This is called as theory of inheritance of acquired characters or Lamarckism.
b. Darwin’s theory of natural selection.
Ans. (1) Charles Darwin, an English biologist published the theory of natural selection, which preaches the survival of the fittest. (2) According to him, all organisms reproduce prolifically. (3) All the organisms compete with each other in a life-threatening manner. (4) In this competition, only those organisms sustain which show the modifications essential for winning the competition. (5) Natural selection also plays important role because nature selects only those organisms which are fit to live and the rest perish. (6) Sustaining and selected organisms can perform reproduction and thereby give rise to the new species with their own specific characters.
c. Embryology.
Ans. (1) Embryology is the study o f developing embryos. (2) C omparative study of embryonic developmental stages of various vertebrates given in the picture shows that all embryos show extreme similarities during initial stages and those similarities decrease gradually. (3) Similarities in initial stages indicate the common origin of all these animals.
d. Evolution.
Ans. (1) Evolution is the gradual change occurring in living organisms over a long duration. (2) This is a very slow-going process through which development of organisms is achieved. (3) All the stages in changes occurred in various components ranging from stars and planets in space to the biosphere present on the Earth should be included in the study of evolution. (4) Formation of new species due to changes in specific characters of several generations of living organisms as a response to natural selection, is called as evolution.
e. Connecting link.
Ans. (1) Some plants and animals show some morphological characters by which they can be related to two different groups; hence they are called as ‘connecting links’. (2) Example (a) In Peripatus, characters like segmented body, thin cuticle, and parapodia-like organs are present. Similarly, these animals show tracheal respiration and open circulatory system similar to arthropods. This indicates that Peripatus is connecting link between annelida and arthropoda. (b) Duck billed platypus lays eggs like reptiles but shows relationship with mammals too due to presence of mammary glands and hairs. (3) These examples indicate that mammals are evolved from reptiles and amphibians from fishes
5. Define heredity. Explain the mechanism of hereditary changes.
Ans. Heredity : Heredity is the transfer of biological characters from one generation to another via genes.(2) Mechanism o f hereditary changes : (i) Mutation : Sudden change in the parental DNA can cause mutations. This results into changes in the hereditary characters. (ii) Natural Selection, (iii) Genetic Drift etc.
6. Define vestigial organs. Write names of some vestigial organs in human body and write the names of those animals in whom same organs are functional. (July ’19) (Nov. ’20)
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(i) Degenerated or underdeveloped useless organs of organisms are called as vestigial organs.
(ii) Appendix is a vestigial organ in humans, but is fully functional in ruminants.
(iii) Muscles of ear pinna are vestigial in humans but are useful in monkey for movement of ear pinna.
7. Answer the following questions.
a. How are the hereditary changes responsible for evolution?
Ans.
(1) Evolution is the gradual change occurring in living organisms over a long duration.
(2) Certain heritable sudden changes may occur in the genes of an individual resulting in genetic variations.
(3) These genetic variations are responsible for the formation of new species from the earlier one.
(4) According to Darwin’s theory, organisms with favourable or beneficial variations survive in competition and are selected by nature whereas the others with non-favourable variations are eliminated.
(4) This leads to formation of new species due to specific changes in specific characters accumulated through several generations in sustained and selected organisms.
b. Explain the process of formation of complex proteins.
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(i) Information about protein synthesis is stored in the DNA and synthesis of appropriate proteins as per requirement is necessary for the body.
(ii) These proteins are synthesized by DNA through the RNA. This is called as Central Dogma.
(iii) mRNA is produced as per the sequence of nucleotides on DNA. Only one of the two strands of DNA are used in this process.
(iv) The sequence of nucleotides in mRNA being produced is always complementary to the DNA strand used for synthesis. This process of RNA synthesis is called transcription.
(v) The mRNA formed in the nucleus comes in cytoplasm. It brings in the coded message from DNA.
(vi) The message contains the codes for amino acids. The code for each amino acid consist of three nucleotides. It is called as triplet codons.
(vii) mRNA is made up of thousands of triplet codons.
(viii) As per the message on mRNA, amino acids are supplied by the tRNA.
(ix) For this purpose, tRNA has ‘anticodon’ having complementary sequence to the codon on mRNA. This is called as ‘translation’.
(x) The amino acids brought in by tRNA are bonded together by peptide bonds with the help of rRNA.
(xi) During this process, the ribosome keeps on moving from one end of the mRNA to the other end by the distance of one triplet codon. This is called as ‘translocation’.
(xii) Many of such chains come together to form complex proteins.
c. Explain the theory of evolution and mention the proof supporting it.
Ans.
(i) According to the theory of evolution, first living material (protoplasm) has been formed in ocean.
(ii) In due course of time, unicellular organism was formed.
(iii) Gradually, changes occurred in the unicellular organism from which larger and more complex organisms were formed.
(iv) All those changes were slow and gradual. Duration of all these changes is about 300 crore years.
(v) Changes and development in living organisms has been all round and multi-dimensional and this led to evolution of different types of organisms.
(vi) Hence this overall process is called as evolution which is organizational.
(vii) Progressive development of plants and animals from the ancestors having different structural and functional organization is called evolution.
(viii) To support the theory of evolution, various types of evidences are available.
(ix) Morphological evidences support the theory. It is seen that all plants have stem, root, leaf and are green in colour and those having green colour carry out photosynthesis. Similarly it is seen that animals have appendages, eyes, nose, ears etc.
(x) Anatomical evidences like the bone structure of a human arm, a bulls leg, a bat’s wing and a whale fin have similar structures attributing that they have developed from common ancestors.
(xi) Vestigial organs like tail bone or coccyx present in humans indicate the link between humans who have lost a tail and monkeys who have a tail.
(xii) At embryological level, similarities are observed during initial stage which indicates common origin.
(xiii) Thus, there are a few evidences which support the fact that evolution is sequential.
d. Explain with suitable examples importance of anatomical evidences in evolution. (July ’19; March ’20)
Ans.
(i) There doesn’t seem any superficial similarity between a human hand, a cat’s foreleg, flipper of a whale and patagium of a bat.
(ii) Use of each of these structures is different in respective animals.
(iii) However, there is a similarity in structure of bones and bony joints in organs of each of these animals.
(iv) This similarity indicates that these animals show anatomical evolution.
e. Define fossil. Explain importance of fossils as proof of evolution. (3 marks) (Sept. ’21)
Ans.
(i) Remnants and impressions of organisms which get buried remain preserved underground. These are called as fossils. Study of fossils is an important aspect of study of evolution.
(ii) Carbon consumption of animals and plants stops after death and since then, only the decaying process of C-14 occurs continuously.
(iii) In case of dead bodies of plants and animals, instead of remaining constant, the ratio between C-14 and C-12 changes continuously as C-12 is non-radioactive.
(iv) The time passed since the death of a plant or animal can be calculated by measuring the radioactivity of C-14 and the ratio of C-14 to C-12 present in their body.
(v) This is carbon dating method. It is used in determining the age of human fossils and manuscripts.
(vi) Once the age of fossil has been determined, it becomes easy to deduce information about other erstwhile organisms. It seem that vertebrates have been slowly originated from invertebrates.
f. Write evolutionary history of modern man.
Ans.
(i) Approximately seven crore years ago, monkey like animals are said to be evolved from some ancestors who were more or less similar to the modern lemurs.
(ii) Tail of these monkey like animals of Africa is said to have disappeared about 4 crore years ago.
(iii) Evolution of some of the 2 crore years old species of apes seems to have occurred in different ways. They had to use their hands more for eating food and other work.
(iv) First human like animal recorded was ‘Ramapithecus’ ape from East Africa.
(v) This ape grew up in size and became more intelligent and evolved about 40 lakh years ago.
(vi) Skilled humans appeared to be the member of genus Homo.
(vii) About 15 lakh years ago, humans walking with erect posture evolved and existed in China and Indonesia of Asian continent.
(viii) Evolution of upright man continued in the direction of developing its brain for the period of about 1 lakh years.
(ix) Brain of 50 thousand year old man had been sufficiently evolved to the extent that it could be considered as member of the class-wise-man (Homo sapiens).
(x) Neanderthal man can be considered as the example of wise-man.
(xi) The Cro-Magnon man evolved about 50 thousand years ago and afterwards, this evolution had been faster than the earlier.