Evolution class 12 Chapter 7
Evolution class 12:- Origin of the life on earth can be understood only against the background of the origin of the universe, especially Earth.
Evolution class 12 – Very Short Answer Type Questions
Q.1. Make a list of the characteristics of fossils.
A.1. Following are the characteristics of fossils are below:
- The fossils provide a connecting link between the different species.
- It help in the identifying the time period when they are existed.
- It represent the modes of the preservation of the different ancient species.
- It helps in identifying the evolutionary traits of the organisms and their ancestors.
Q.2. How can we estimate the age of living tree ?
A.2. The age of living tree can be calculated by the counting of the annual rings on the wood growth.
Q.3. Write the name of the process to estimate the age of a fossil.
A.3. The age of a fossil is estimated by the process of carbon dating.
Q.4. What do you meant by the precondition for adaptive radiation?
A.4. The pre-condition for the adaptive radiation is forming the physical and the geographical barriers between the population of the same species.
Q.5. How can we estimate the age of rock ?
A.5. The age of the rock is estimated by the measuring of the amount of certain radioactive elements in the rock. Age of the rock is called as the absolute age.
Evolution class 12 Quiz
Q.6. What do you meant by the founder effect?
A.6. The founder effect is a type of the genetic drift that occurs when a few individuals in the population separate from their original population and form a colony. The Genetic diversity of the new population will not be the as same as that of the original population. This is a gradual process.
Q.7. What do you meant by the bottleneck effect?
A.7. The bottleneck effect is a type of the genetic drift that occurs when the size of a population is severely reduced because of the events such as earthquakes, epidemics, floods, fire, etc. In this process, the large number of organisms are deceased leaving behind only the handful of the population. Now, the genetic diversity of the surviving the population becomes the genetic diversity of the entire population.
Q.8. Define natural selection.
A.8. The natural selection is the process in which the survival and the reproductive rate of individuals with certain characteristics are greater than that of the other individuals in the population. This process leads to an evolutionary change in the environment.
Q.9. Which factors affecting the Hardy-Weinberg equilibrium?
A.9. Following are the factor which affects the Hardy-Weinberg equilibrium are:
- Genetic Recombination
- Gene Flow
- Genetic Drift
- Natural Selection
Q.10. Write the various stages of evolution.
A.10. There are seven stages in human evolution they are:
- Homo Erectus
- Homo Sapiens Neanderthalensis
- Homo Sapiens Sapiens
Evolution class 12 – Short Answer Type Questions
Q.1. What is the meaning of the “survival of the fittest”?
A.1. This term “survival of the fittest” was coined by Darwin in support of his theory of the natural selection. The organisms that adapt to the changing environmental conditions and overcome the competitions for the food and the space are selected by the nature to survive. In very simple terms, the organisms which are physically in good shape and the health are considered “fit”. The ones which are not are eliminated. This is called as “survival of the fittest”.
Q.2. Give Comment on the statement, “Migration may increase or decrease the effects of the selection”.
A.2. The Migration is the movement of the individuals from one place to the another. The individuals can either move to the different population or move into the particular population. The Movement of the individuals to a different population might remove certain alleles which confer better adaptations. The Movement into a particular population might add certain alleles which blur the effects of selection. Therefore we can say that migration can increase or decrease the effects of selection.
Q.3. Describe the given terms:
- Race–The Race may be a different phenotypic population within the same species. This is used as a rank which is higher than the strains but lower than the species.For Example, Mongoloid, Negroid
- Breed– The Breed is a morphologically and the physiologically distinct sub-group of the race where the crossing occurs within the sub-group to maintain its individuality. For example, Rhode island red, Plymouth red.
- Cultivars– This is a group of the plants selected by the plant breeders for desirable characteristics which can be maintained by propagation. Eg., roses, daffodils
- Variety– This is a morphologically, physiologically, and genetically distinct sub-group of the species. For example, cauliflower, cabbage
Q.4. How can we say that the nascent oxygen is toxic to aerobic living organisms?
A.4. The Nascent oxygen is very reactive and they can react with all the types of biomolecules present in the living organisms, such as the DNA, proteins and the enzymes. That can cause the mutation in the DNA and can degrade the proteins and the enzymes on reactions, therefore, toxic to aerobic life forms.
Evolution class 12
Q.5. The Creation and the presence of variation are directionless, but the natural selection is directional as it is in context of the adaptation. Comment.
A.5. The Variation is considered as directionless because it is the spontaneous and the random. It is seen in the sexually reproducing organisms that occurs as a result of the crossing over during meiosis or the fusion of gametes. The variations that helps in the individuals in adapting to the environment are passed on to the successive generations. The Natural selection is directional due to it leads only to one path, i.e., the selection. It is an evolutionary change which leads to the survival of the fittest and the elimination of the unfit individuals.
Q.6. Comment on the given statement with the reference to the industrial melanism, “Evolution is apparently reversible”.
A.6. The peppered moth resided on the surface of the lichens and they protected itself from the predators due to the camouflage. During the industrialization in Europe, the surface of lichens turned black due to the emissions from the coal-based industries. The moths were now easily visible to the predators and they got the eliminated gradually. A mutant of the peppered moth they flourished during this period. It was not visible to the predators due to the its black colour and therefore it was selected by nature. The clean air legislation was passed in the Europe in 1956 as a result of which the emission of smoke decreased. The non-melanic peppered moth is the appearing again along with the lichens. This is the proves that evolution is reversible.
Evolution class 12 study materials
Q.7. Define genetic drift.
A.7. Genetic drift is the mechanism of evolution in which the allele frequencies change over the generations as a matter of the chance. It occurs in the populations of all sizes but it the effect is the maximum in a small population. The Genetic drift is observed when there is a sudden decline in the population because of natural disasters (bottleneck effect), or when the new population separates from the original population to form a colony (founder effect). The Genetic drift does not take into the account whether the allele is beneficial or harmful to the individual carrying it. This is possible that a beneficial allele is lost and the harmful allele persists.
Q.8. Describe the adaptive radiation. Also give the examples in support of your answer.
A.8. The Adaptive radiation is the process in which the living organism diversifies from a single ancestor into the multiple new forms. This is mainly because of changes in the environment. The Darwin’s Finches is one of the fine example of adaptive radiation. The finches of the Galapagos island are seen with a variety of beaks depending upon the type of food they feed on. A single species got adapted to environmental and the nutritional conditions and they developed respective beak types over the years.
Q.9. What is the difference between the convergent evolution and the divergent evolution?
A.9. When the two or more species belonging to the different ancestors develop similar characteristics because of the adaptation to a particular environment, this is called as the convergent evolution. On the contrary, when the species belonging to the same ancestors develop different characteristics because of the environmental changes and they evolve into the some new species, it is called as divergent evolution.
Evolution class 12
Q.10. Explain about the Hardy-Weinberg principle.
A.10. The Hardy-Weinberg principle states that in a large population which is not affected by the evolutionary processes such as the mutation, selection or migration, the allele frequencies and the genotype frequencies are the constant from one generation to the other. This principle can be explained by the simple equation: (p+q)2 = p2 +q2 + 2pq = 1 Where, this are p = frequency of allele A q = frequency of the allele a p2 = frequency of the individual AA q2 = frequency of the individual aa 2pq = frequency of the individual Aa.
Q.11. How can we say that the genetic variation help in the evolution?
A.11. The Genetic variation is important in the evolution allows the natural selection to increase or decrease the frequency of the alleles already present in the population. This variations enable the few individuals to adapt to the environment.
Evolution class 12 – Long Answer Type Questions
Q.1. Write the key concepts in the evolution theory of the Darwin.
A.1. The two key concepts of the Darwin’s theory of evolution are:
- Branching Descent
- Natural Selection
Branching Descent- This is the process in which the new species originate from a single ancestor. They became adapted to the the new environment through the reproductive isolation. For example., The Darwin’s finches that evolved from a single grain eater species.
Natural Selection- In this process, the variations in an individual facilitate the better survival of the species. They reproduce in the large numbers. These variations are passed on to the successive generations that helps them to survive in the changing environmental conditions. For example, few giraffes have the long necks while the others have short necks. If the low-lying shrubs are the eliminated for some reason, the giraffes with the short necks would be replaced by the giraffes with the long necks.
Evolution class 12
Q.2. Explain the phenomenon in which the two organisms occupying the same geographical area show the same strategies of adaptation.
A.2. The phenomenon is the convergent evolution. In this process, the two organisms belonging to the different species, descending from the different ancestors, evolve similar traits in order to adapt to the similar environment. For example., the streamlined body of the sharks and the dolphins. The Sharks are fishes while the dolphins are mammals but both of them have developed the streamlined bodies to adapt themselves to swift swimming. The Spines are modified leaves and the thorns are modified stems. Both look alike and have a similar function of the protecting the plants, but they are distantly related to each other.
Q.3. Which driving force is behind the divergent evolution? Explain it.
A.3. The adaptation is the driving force behind the divergent evolution. The Divergent evolution is the phenomenon in which organisms descending from the common ancestors evolve gradually into a the new species. The new species thus formed adapt themselves to the new habitat and environmental conditions. For example, the forelimbs of bats, cheetahs, whales and humans have the same anatomical structures but they perform the different functions. Thus, in these animals, the same structure evolved into the different forms according to the needs of the animals.
Q.4. Which law states that the sum of the allelic frequencies in the population is constant? Make a list of the five factors that influence this law.
A.4. This law is the Hardy-Weinberg equilibrium. Following are the five factors influencing this law are:
- Genetic drift
- Gene flow
- Genetic Recombination
- Natural Selection
Q.5 What impact would it have on the population of moths in England, if the industries were removed?
A.5. The two variants of the peppered moths, the black and the grey, were already existing in the population. This is resided on the surface of the lichens. Before the industrialization, the grey moths were not spotted by the predators because of the camouflage. Therefore, the black moths were easily visible and they killed by predators. If the industries got removed, the population of the black variants would have the reduced to a large extent leaving behind the grey population of peppered moths.
Q.6.Write the different types of evolution.
A.6. Following are the different types of evolution:
- Convergent evolution– This is the process, that evolves independently, under the similar selection pressures. Examples of convergent evolution flying insects, birds and other flying species have all evolved the ability to fly, but they are independently of each other.
- Coevolution evolution–This is the process in that two or more species evolve in the tandem by exerting the selection pressures on each other. Example of coevolution evolution, the host and the parasites, predators and the prey, the flowering plants and the pollinating insects and the mutualistic or symbiotic interactions.
- Adaptive radiation–Thia is the process in that a species splits into a number of new forms when the change in the environment makes the new resources available or creates the new environmental challenges. Example of adaptive radiation, the finches on the Galapagos Islands have the developed different shaped the beaks to take advantage of the different kinds of food available on the different islands.
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