Gujarat Board GSEB Textbook Solutions Class 12 Biology Chapter 7 Evolution Textbook Questions and Answers, Additional Important Questions, Notes Pdf.
Gujarat Board Textbook Solutions Class 12 Biology Chapter 7 Evolution
GSEB Class 12 Biology Evolution Text Book Questions and Answers
Explain antibiotic resistance observed in bacteria in light of Darwinian selection theory.
According to Darwin excess use of antibiotics or drugs has resulted in selection of resistant varieties in a much lesser time scale, i.e., the resistant organisms or cells are appearing in a time scale of months or years and not centuries. It is an example of evolution not by nature by anthropogenic action.
Find out from newspapers and popular science articles any new fossil discoveries or controversies about evolution.
- Fossil of a small terrestrial dinosaur with feathers covering limbs and body. (Archaeopteryx lithographic)
- Mesohippus – intermediate horse size of goat with 3 toes on each foot and molar teeth had serration.
Attempt giving a clear definition of the term species.
According to Dobzhansky, species are mostly included in the Mendelian population, which share the common gene pool. According to Mayr, species are the groups of actually or potentially interbreeding natural populations that is reproductively isolated from other such groups.
Try to trace the various components of human evolution (hint: brain size and function, skeletal structure, dietary preference, etc.)
Find out through internet and popular science articles whether animals other than man has self-consciousness.
List 10 modern-day animals and using the internet resources link it to a corresponding ancient fossil. Name both.
Practise drawing various animals and plants.
Describe one example of adaptive radiation.
Adaptive radiation – Formation of different species from a common ancestor with new species adapting to different geological niches.
Example: Darwin’s finches is Galapagos island have wolves from mainland finches. They underwent changes in shape, size of beaks, food habit, feathers.
Can we call human evolution adaptive radiation?
No. Human evolution is totally different from the evolution of other animals.
Using various resources such as your school library or the internet and discussions with your teacher, trace the evolutionary stages of any one animal, say horse.
GSEB Class 12 Biology Evolution Additional Important Questions and Answers
To support the Big Bang theory, an experiment was done in 2008.
a. Name the experiment.
b. Where is it done?
a. Large Hydron Collider
b. This is done under the earth’s surface of the boundary between Switzerland and France.
What are fossils?
Fossils are the remnants or traces of ancient organisms that lived in the past.
Fossils are organic relies on the past which serves as evidence in tracing biological evolution.
It is possible to make a living cell with the help of methane, ammonia, water, and hydrogen. Do you agree with this statement?
Yes. This was confirmed by an experiment done by Urey and Miller in 1953. At the end of the experiment, they got simple organic compounds which included amino acids like glycine, alanine and aspartic acid, fatty acids, and urea. As we know, amino acids are the basic units of protein and fatty acids are the basic unit of lipids, it is possible to make a living cell with the help of these elements.
This is a type of adaptive radiation seen in one part of the world.
a. Identify the type of adaptive radiation. Where is it seen?
b. Give the difference between convergent evolution and divergent evolution.
a. Marsupial radiation seen in Australia.
b. Convergent evolution: When more than one adaptive radiation appeared to have occurred in different habitats or isolated geographical areas, it is called convergent evolution.
Divergent evolution: The process of evolution of different species in a given geographical area starting from a point and literally radiating to other areas of habitats (geography) is called divergent evolution or adaptive radiation.
The above-shown pictures are of a type of bird seen on an island near South America.
a. Identify the island.
b. What is the significance of these birds in evolution?
a. Galapagos islands. This is a chain of 14 islands in the Pacific ocean situated nearly 960 km away from the west coast of South America.
b. They are the Darwin finches. This is a classical example of adaptive radiation forwarded by Charles Darwin.
The diagrammatic representation shows the operation of natural selection. Give suitable heading for these curves.
a. Stabilising curve
b. Directional curve character value.
c. Disruptive curve – More individuals acquire peripheral character value at both ends of the distribution curve.
Give the names of
a. biggest reptile,
b. first mammal
c. first fossil of human evolution.
d. first fossil of horse evolution.
a. Tyrannosaurus rex
c. Dryopithecus and Ramapithecus
Correct the flowchart of vertebrae according to the geological period. Old to new.
Find out the odd one in each group.
a. Cat’s paw, insect wings, horse foot, bat’s wing, human hand.
b. Industrial melanism, mutation, genetic drift, gene migration.
c. Vermiform appendix, plica semilunaris, spleen, pelvic girdle of python, cervical fistula.
d. Coenozoic, mesozoic, palaeozoic, proterozoic, holozoic
e. Isolation, recombination, genetic drift, gene migration, natural selection, mutation, speciation.
a. insect wings
b. Industrial melanism
Give reasons for the following.
a. Frog tadpole excretes ammonia, adult frog excretes urea.
b. The chemical composition of DNA in almost all animals is similar.
c. For energy production all animals depend upon glycolysis and Kreb’s cycle. Connecting links play an important role in understanding the concept of organic evolution.
e. Change in germ cells is heritable.
f. Genetic drift is also known as bottleneck phenomenon.
a. Excretion of ammonia needs more water. Urea needs only a little water for excretion.
b. Supposed to have a common ancestor.
c. common ancestry.
d. These animals have the characters of both aves and reptiles.
e. The information in the germ cells is only transferred to the next generation whereas in the somatic cells it is not.
f. Reduction in gene frequencies.
Birds are glorified reptiles. Justify the statement.
Features of Archaeopteryx.
a. Presence of beak (like birds) and teeth (like reptiles).
b. Presence of wings (like birds) and clawed digits (like reptiles).
c. Presence of feathers (like birds) and scales (like reptiles).
d. Presence of feathery tail (like birds) and tail vertebrae (like reptiles).
Write the names of two dinosaurs that lived early in geological history and two that lived later.
- Lived early in the geological history:- Brachiosaurus and Stegosaurus
- Lived later:- Triceratops and Tyrannosaurus.
Archaeopteryx is considered as a connecting link between birds and reptiles. Justify the statement by giving two characters of each group.
Fossils indicate the connecting link between two groups of organisms. For example, Archaeopteryx shows the features of both reptiles and birds. The toothed beak, clawed digits, feathers (modified scales), tail vertebrae, etc. of Archaeopteryx indicate that the birds have evolved from reptiles. Hence Archaeopteryx is called a reptile bird. Wegner in 1861, discovered this fossil bird. These features justify Huxley’s statement that the birds are glorified reptiles.
Name one organ analogous to the wings of a bird. Why are they both analogous. Can you include wings of the bat also with them under the same category? Give reason. (CBSE 1997)
Wings of insects and birds are analogous because both perform the sante function but have dissimilar structured and origins. The wings of insects have modified outgrowth of the body without having bones, whereas the wings of birds are modified forelimbs.
The wings of bat cannot be put under the same category. This became the wings of a bat and birds are homologous organs.
Mention the role of cyanobacteria in origin of life.
Cyanobacteria is considered the first animal to evolve on earth. They were aerobic phototrophs. The fossil study reveals that those were similar to today’s cyanobacteria.
The universe had an explosive beginning’. Which theory proposes this?
Big Bang theory
There are many unusual organisms reported in Australia because of some special evolution. Mention the speciality of evolution that have occurred for the past 38 million years.
Match the following related things from B and C with column A
|a. Mutation theory||Lemaitre||Result of explosion|
|b. Big Bang theory||de Vries||Evolution is not a continuous process|
|c. Biogenesis||Aristotle||Life from non – living thing|
|d. Abiogenesis||Redi||Life from living thing|
|a. Mutation theory||Lemaitre||Evolution is not a continuous process|
|b. Big Bang theory||de Vries||Result of explosion|
|c. Biogenesis||Aristotle||Life from living thing|
|d. Abiogenesis||Redi||Life from non – living thing|
Match the following related things from B and C with Column A.
|a. Mesozoic era||Tertiary||Age of reptiles|
|b. Cenozoic era||Permian||Age of amphibian|
|c. Palaeozoic er||Jurassic||Age of mammals|
|a. Mesozoic era||Jurassic||Age of reptiles|
|b. Cenozoic era||Tertiary||Age of amphibian|
|c. Palaeozoic er||Permian||Age of mammals|
Identify the following figures.
Fossils reveal the existence of life in the past and illustrate the course of evolution. The significance of fossils are the following.
i. Fossils are the dead remains of the past.
ii. They help to study the structure, traits and behaviour of extinct animals.
iii. They give an idea about the form and structure of extinct animals.
iv. They help to study the phylogeny (evolutionary history or race history) of some animals such as horses, camels, man etc. Eg. Horse evolution. Eohippus (dog-like animal lived 54 million years ago), Mesohippus (lived 38 million years ago) and Merychippus (lived 25 million years ago) show the various stages in the evolution of the horse. All are extinct. Genera Equus (modern horse) is the living horse.
v. Fossils indicate the connecting link between two groups of organisms. For example, Archaeopteryx shows the features of both reptiles and birds. The toothed beak, clawed digits, feathers (modified scales), tail vertebrae etc. of Archaeopteryx indicate that the birds have evolved from reptiles. Hence Archaeopteryx is called reptile bird. Wegner in 1861, discovered this fossil bird. These features justify Huxley’s statement that the birds are glorified reptiles.
vi. The time in history when different species were formed or became extinct can be inferred through the analysis of the distribution of fossils in different strata of rocks.
The population of grey coloured Biston betularia, were almost replaced by the black variety during the industrial revolution in England. Explain the mechanism involved.
Correct the following chart showing Darwinism.
Aristotle believed that fishes originated from mud, insects from decaying meat, a frog from moist soil, etc. Do you agree with this statement? If no, give a reason.
No. Louis Pasteur disapproved of this theory. Louis Pasteur’s swan neck experiment.
Give a detailed account of the theory of natural selection.
Describe Darwin’s opinion about the origin of new species of organisms.
Charles Darwin (1809-1882) explained the theory of evolution in his book “Origin of species by natural selection.” Darwin undertook a long voyage for five years in the capacity of a naturalist on a British warship ‘Beagle’. He traveled to the islands of the Galapagos and collected evidence to explain evolution.
To explain the origin of species he gave the theory of natural selection as a mechanism for evolution.
The main points of Darwinism are given below:
- Over-production of offsprings: Every living being has an inherent tendency to produce more offspring than that can survive.
- Struggle for existence: Though the offsprings are produced in large numbers yet their production remains almost constant. This is because of the struggle for existence. There is a struggle for food, space, breeding, etc. Moreover death of individuals due to diseases an
- Survival of the fittest: Darwin believed that any individual is successful in the struggle for existence if it survives long enough to produces offsprings. Individuals who are fit in a particular environment can only survive.
- Variation: Due to constant struggle, the organisms change themselves in accordance with the new needs.
- Natural selection: In the struggle, for existence organisms having variations favourable to the environment would have more chance to survive and reproduce their own kind. Those which do not possess favourable variations would die or fail to reproduce.
- Origin of species: Any changes in environmental conditions cause natural selection to act upon the population and select the well-adapted individuals. It results in changes in the characters of the populations. By the inheritance of these changes in successive generations, new species are formed.
Is there any population in Kerala having sickle cell anaemia? What is the reason for this genetic defect? Does it help the people in preventing any other diseases like malaria?
Yes. In high altitude persons. It is a genetic defect characterized by sickle-shaped RBC with abnormal Hb.
a. Identify the personalities shown above.
b. Briefly give about their contributions to evolution.
a. A – Lamarck, B – Darwin
b. Lamarckism or Inheritance of acquired characters.
Darwinism or Natural selection.
The national geographic channel selected you to interview Lamarck, the famous evolutionist. Prepare some questions to be asked.
Make some questions about his life history, Lamarckism and criticism to theory.
Examine carefully the details given and group similar ones in table. Give suitable title for each column. Analyse the importance of each group in evolution.
Patagium of Draco, human hand, forelimb of rabbit, wings of bird, vermiform appendix, plica semilunaris, wings of insects, whale’s flipper, ear muscles.
|Vestigial organs||Homologous organs||
|Vermiform appendix||Human hand||Wings of bird|
|Plica semilunaris||Forelimb of rabbit||Wings of insect|
|Ear muscles||Whales’ flipper|
Study the figures (a) and (b) given below and answer the questions given after the graphs.
i. Under the influence of which type of natural selection would graph (a) become like graph (b)?
ii. What could be the likely reasons of new variations arising in the population?
iii. Who suggested natural selection as a mechanism of evolution?
i. This is disruptive selection. It is just opposite of stabilising selection, i.e., the extremes are more adaptable than the average ones.
ii. Population becomes adapted if its individuals have some new trait (genetic variation) which suits the changed environment and is selected by nature on this basis. That is spread by differential reproduction and in time becomes a standard feature of a section of the population. This is the unit of evolutionary change.
iii. Darwin and Wallace suggested natural selection as a mechanism of evolution.
How did Louis Pasteur successfully demolish the popular theory of spontaneous generation?
It was believed that living organisms (life) arose from decaying matter like straw. But Louis Pasteur demonstrated that life can arise only from preexisting life. He said that no life arose from the heat-killed yeast broth that was kept in a pre-sterilized flask kept closed, while new living organisms arose from the heat-killed yeast that was kept in the flask left open.
How is the ‘sixth episode of extinction’ of species on earth, now currently in progress, different from the five earlier episodes? What is it due to? Explain the various causes that have brought about this difference.
Sixth episode of extinction is due to the climatic changes that killed them. Five episode that extinct today are
- early reptiles
The sixth episode contains turtles, lizards, snakes, tuataras, crocodile, birds and mammals.
Some are facing danger and are very near to extinct, e.g. the population of white Bengal tiger is decreasing rapidly due to unlimited hunting to make money.
The land reptiles i.e., dinosaurs, suddenly disappeared from the earth (mass extinction) about 65 million years ago due to the changes in climate, while the small sized reptiles continue to exist even today.
How does the shift in Hardy-Weinberg equilibrium leads to a founder effect. (Delhi 2008)
A shift in Hardy – Weinberg equilibrium is caused by factors like gene migration, gametic drift, mutation, etc. Gene migration refers to a change in the gene frequencies of the populations when a section of a population migrates to another place and population.
If gene migration occurs a number of times there would be a gene flow. i.e. new genes/ alleles are added to the new population while they are lost from the original population.
Genetic drift refers to change in allele/ gene frequency at random or that occurs due to some chance event. Sometimes, the change in allele frequency is so different in the new sample of the population that they become different species. The original drifted population becomes the founder and the effect produced is called the founder effect.
What is the evidence for evolution?
Following are the evidences for evolution.
- Some fossils appear similar to modern organisms. They represent extinct organisms.
- The study of fossils in different sedimentary layers indicates the geological period in which they existed.
- The studies showed that the life forms varied over time and certain life forms are restricted to certain geological time-spans. Then new forms have arisen at different times in the history of the earth.