HEREDITY AND EVOLUTION EXERCISE QUESTIONS

 

Q.2 Read the following statements and justify

a)   Human evolution began approximately 7 crore years ago.

• The last dinosaurs disappeared approximately 7 crore year ago due to changes in environmental conditions.
• Monkey like animals evolved from lemur – like ancestors
• 4 crore years ago – The tail of these animals disappeared & brain enlarged. This resulted in formation of Ape-like animals.
• 5 crore years ago, in Africa, Chimpanzees & Gorillas evolved.
• From these, almost 2 crore years ago, Human –like animals developed who used their hands for work.
• Their lumber bones and erect posture developed.
• This gave rise to First human –like ape in east Africa.
• From this, it can be said that, human evolution began 7 crore years ago

       b) Geographical and reproductive isolation gradually leads to speciation

• Speciation – Formation of new species.
• Each species has different food, habitat, reproductive ability and period.
• Speciation can occur either through geographical isolation or reproductive isolation
• Geographical isolation – It occurs when species are separated due to geographical barriers like river, ocean, etc. It exposes organisms to different geographical conditions and speciation occurs.
• Reproductive isolation – It is change in genetic material and structure of genital organs which gradually results in speciation
• C) Study of fossils is an important aspect of study of evolution
• Due to various natural calamities like earthquake, landslides, various living organisms get buried deep down the earth surface.
• The remnants and impressions of these organisms remain preserved underground
• Due to these processes, fossils get formed.
• Study of fossils help researcher to understand the characteristics of organisms.
• We can also decide the exact age of fossils with the help of carbon dating method.
• Age of fossils can be calculated by measuring radioactivity of C-14 and the ratio of C-12 to C-14 present in the body.
• According to structure of earth crust, fossils of various organisms occur at various levels.
• The oldest fossils are obtained at the depth while the relatively recent ones occupy the upper surface.
• The fossils of invertebrates were buried in deep layers and belong to Paleozoic era. The fossils of Pisces, Amphibians and reptiles were obtained in next layers. The Mesozoic era was obtained by reptiles and Cenozoic era showed presence of Aves and Mammals.
• Thus, with the help of fossils, we get information about our ancestors.

1. D) There are evidence of fetal science among chordates.

• Comparative study of development in different sexually reproducing organism like fish, amphibians, mammals shows that there are extreme similarities during initial stages and those similarities decrease gradually.
• This indicates that, all these have evolved from a common ancestor.

3. Complete the statements by choosing correct options from bracket.

 (Gene, Mutation, Translocation, Transcription, Gradual development, Appendix)

1. The causality behind the sudden changes were understood due to Mutation principle of Hugo de Vries.
2. The proof for the fact that protein synthesis occurs through gene was given by George Beadle and Edward Tatum.
3. Transfer of information from molecule of DNA to mRNA is called as transcription
4. Evolution means gradual development
5. Vestigial organ appendix present in human body is proof of evolution

Q.4 Write short notes.

1. Lamarckism-

• This theory was proposed by Jean Baptiste Lamarck.
• It is also called as Theory on inheritance of acquired characters.
• It is based on the concept of Use and disuse of organs.
• It says that morphological changes occurring in living organisms are responsible for evolution. Morphological characters develop because of specific activities of an organism.
• Morphological changes take place due to activities or laziness of a particular organism.
• All organisms can transfer quired characters to next generation. This is called Ancestry of acquired characters

Examples:

• Long neck of giraffe is due to browsing on leaves of tall plants.
• Wings of Ostrich became weak due to no use.
• Snakes lost limbs due to burrowing habit.
• Shoulders of ironsmith become strong due to frequent hammering.
• Legs of ducks have modified for swimming.

Objections:

Modifications are not always transferred to next generation

1. b) Darwin’s Theory-

• It was published in book “Origin of Species”
• It is based on concept of survival of fittest.
• Darwin stated that, Organisms reproduce prolifically.
• Under limited resources, they compete with each other for survival.
• Only those organisms survive which show useful modifications.
• Nature selects fit organisms and others perish.
• Selected organisms give rise to new species.

Objections:

• Natural selection is not the only factor for evolution.
• Didn’t explain about useful and useless modifications.
• No explanation about slow and abrupt changes.

1. d) Evolution –

• Evolution can be defined as gradual changes occurring in organisms over a long duration of time.
• It is a slow-going process.
• Formation of new species occur due to changes in specific characters.
• It takes millions of years for development of new species.
• Changes get accumulated in several generations due to natural selection and new species are formed.

1. e) Connecting link –

• Some plants and animals show morphological characters by which they can be related to 2 different groups of organisms. These are called connecting links.

1. Peripatus – Annelids and Arthropods.

         Annelid characteristics:

Segmented body, thin cuticle, parapodia like organs.

        Arthropod characteristics:

• Trachea for respiration, open circulation

2. Duck billed Platypus – Mammals and Reptiles.

       Mammalian characteristics:

• Mammary glands and hair on body.

       Reptilian characteristics:

• Lays eggs.

3. Lung fish –Fishes and Amphibians.

        Amphibian characteristics:

• Lungs for respiration

        Pisces characteristics:

• Fish like body.

Q.5 Define heredity. Explain mechanism of hereditary changes.

It is transfer of biological characters from one generation to other via genes.

Mechanism of hereditary changes –

• Diversity occurs due to genetic variation.
• In sexually reproducing organisms, fusion of gametes leads to formation of offspring having recombined genes of both the parents. This leads to development of new characters.
• Sometimes due to mutations also cause major or minor changes in characters.
• Changes in DNA transfers the characters to next generation.

 Q.6 Define vestigial organs. Write names of some organs which are functional in other animals.

These are degenerated or underdeveloped useless organs.

Ex.

1. Appendix – functional in ruminants for digestion of cellulose.
2. Muscles of ear pinna – Useful in monkeys and animals like cows, horses, etc. for movement of ears.
3. Tail bone / Coccyx – Functional in animals having tail.
4. Body hair – Useful for insulation of body in animals
5. Wisdom teeth – It is functional in grass eaters for digestion of cellulose in food.
6. Nictitating membrane / Plica semilunaris / third eyelid.

Q.7 Answer the following.

1. How are the hereditary changes responsible for evolution?

• Evolution is gradual change in living organisms over a long duration.
• Certain heritable changes may occur in the genes of an organism resulting in genetic variations.
• These genetic variations are responsible for formation of new species.
• According to Darwin, favorable variations survive and non-favorable variations are eliminated.
• Thus, new species are formed due to specific changes in characters.

1. Explain the formation of complex proteins.

The process of synthesis of proteins from DNA through RNA is called the central dogma.

It occurs in 3 steps – Transcription, translation, translocation.

1. Transcription –

• It is the process of synthesis of mRNA from DNA
• Takes place in presence of RNA polymerase
• The information from DNA is copied from one molecule to another
• DNA creates mRNA to deliver its information out the nucleus
• First, the double helix of DNA is unwound by RNA polymerase
• As the double helix unwinds, ribonucleotide bases (A, C, G, U) attach the molecules of DNA strand by complementary base pairing by covalent bonds and then it recoils.
• When it is released from DNA, the mRNA now comes in cytoplasm with the coded message from DNA
• The message contains codes for amino acids which consist of 3 nucleotides. hence, they are called triplet codons.

2. Translation-

occurs in the following manner:

• Once the mRNA has left the nucleus, it is directed to a ribosome to construct a protein.
• Ribosome attaches to the mRNA molecule.
• tRNA act as couriers as per the message on mRNA, amino acids are supplied by tRNA.
• tRNA has anticodon having complementary sequence to the codon on mRNA
• The amino acids brought in by tRNA are bonded together by peptide bonds with the help of rRNA

3. Translocation –

During the process of transcription, the r-RNA continues as the ribosome moves along the entire length of the mRNA by a distance of one triplet codon, also known as translocation.

In this way, many such chains of amino acids (peptides) come together to form complex proteins.

c) Explain the theory of evolution and mention proof supporting it.

• According to this theory, the first living material was protoplasm. Which was formed in oceans.
• From this, unicellular organisms developed.
• After almost 300 crore years later, gradual changes occurred in the unicellular organisms and larger and more complex organisms developed.
• All round and multidimensional changes occurred in them which resulted in formation of plants animals from ancestors having different structural and functional organization.
• Progressive development of plants and animals from the ancestors having different structural and functional organization is called evolution
•   The proofs supporting the theory of evolution include morphological evidence, anatomical evidence, vestigial organs, paleontological evidence, connecting links and embryological evidence.

D) Explain importance of anatomical evidences.

1. Anatomical evidences are the similarities in structures and anatomy between different organisms.
2. The hand of human, foreleg, of ox, flipper of whale and forelimbs of bat appear different superficially or morphologically.
3. Also, the function of these structures is different in different animals.
4. However, there is a similarity in the structure of bones and bony joints in the organs of these animals.
5. These similarities indicate that the animals evolved from common ancestor thus providing proof of evolution.

E) Explain importance of fossils as proof of evolution.

• Fossils – dead remains of plants and animals that lived in the past.

OR

The remnants and impressions of organisms that remain preserved underground

• Due to various natural calamities like earthquake, landslides, various living organisms get buried deep down the earth surface.
• The remnants and impressions of these organisms remain preserved underground
• Due to these processes, fossils get formed.
• Study of fossils help researcher to understand the characteristics of organisms.
• We can also decide the exact age of fossils with the help of carbon dating method.
• Living organisms continuously interact with each other and exchange carbon.
• When they are dead, this process of carbon consumption stops completely.
• The carbon is present in 3 main isotopes – C-12, C-13, C-14. Of these, C-12 and C – 13 are comparatively stable while C-14 is quite unstable and undergoes continuous decay after the death of organism.
• Thus, the ratio of C-12 to C-14 changes continuously.
• Age of fossils can be calculated by measuring radioactivity of C-14 and the ratio of C-12 to C-14 present in the body.
• According to structure of earth crust, fossils of various organisms occur at various levels.
• The oldest fossils are obtained at the depth while the relatively recent ones occupy the upper surface.
• The fossils of invertebrates were buried in deep layers and belong to Palaeozoic era. The fossils of Pisces, Amphibians and reptiles were obtained in next layers. The Mesozoic era was obtained by reptiles and Cenozoic era showed presence of Aves and Mammals.
• Thus, with the help of fossils, we get information about our ancestors.

   F) Write evolutionary history of man.

• It began approximately 7 crore years ago.
• The last dinosaurs disappeared 7 crore years ago.
• Ancestors of humans developed from animals which resembled modern lemur like animals.
• After about 4 crore years ago, in Africa, the tails of these monkey-like animals disappeared gradually.
• From these, developed ape–like animals (Aegyptopithecus) due to enlargement of brain and improvement in hand functioning.
• Some of the Aegyptopithecus migrated to South and North East Asia from which apes like Gibbons and Orangutan developed.
• While some stayed in Africa which developed into Gorilla and Chimpanzees around 2.5 crore years ago.
• From these, developed Dryopithecus.
• 2 crore years ago, human like animals who used hands for eating and other work were evolved.
• Due to reduction in forests, the apes started living on land.
• Due to this, there were changes in the structure of their vertebral column and lumbar bones.
• Thus, they were able to stand in an erect posture and their hands became free for use.
• The first record of human like ape in East Africa was Ramapithecus (About 1 crore years ago)
• Around 40 lakh years ago, these apes grew in size and became more intelligent (Australopithecus)
• Around 20 lakh years ago, human like animals shared morphological similarities with the members of genus homo, and skilled human developed.
• Around 15 lakh years ago, human walking with erect posture evolved that may have existed in China, Indonesia and Asian subcontinent.
• Neanderthal man who was considered as the first wise man, was evolved around 1.5 lakh years ago.
• For around 1 lakh years from then, cranial capacity of man increased.
• Man also discovered fire.
• The brain of 50000-year-old man evolved in such a way that, he could be considered as the member of wise man (Homo sapiens)
• Cro magnon man evolved around 50000 years ago.
• Now the evolution became faster.
• 10,000 years ago, Man started practicing agriculture, cattle rearing, establishing cities.
• Then cultural development started
• 500 years ago, Art of drawing developed
• 400 Years ago, Modern Science developed
• 200 years ago, Industrial society was established.