Few problems along with their solutions from this chapter are given follows:
Q.┬аThe theory of spontaneous generation stated that
(a) life arose from living forms only
(b) life can arise from both living and non-living
(c) life can arise from non-living things only
(d) life arises spontaneously, neither from living nor from the non-living.
Ans.┬а(c) life can arise from non-living things only┬а┬а┬а┬а┬а┬а
The theory of spontaneous generation stated that an obsolete┬аtheory┬аthat states that living organisms can originate from inanimate (non-living) objects. It is also known as abiogenesis.
Q.┬аVariations during mutations of meiotic recombinations are
(a) random and directionless┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а
(b) random and directional
(c) random and small┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а┬а
(d) random, small and directional
Ans.┬а(a) random and directionless┬а┬а┬а┬а┬а┬а
Variations during mutations of meiotic recombination are random and directionless. Hugo de Vries based on his work on evening primrose stated that it is mutation which causes sudden appearance of variations that results in speciation.
He stated that mutations are sudden, heritable and persistent in successive generation. He contradicted Darwinian variations that are small and directional.
Q.┬аWhat is founder effect?
Ans.Sometimes, a small number of individuals become isolated from a larger population to form a new population at some distance away from their place of origin.The gene pool of the new population differs from the source population. It is possible that the change in allele frequency is so drastically different in the new sample that they become a different species. The original driftted population becomes founders and this effect is called founder effect.
Q.┬аEnumerate three most characteristic criteria for designating a Mendelian population.
Ans.┬а┬аThree most characteristic criteria for designating a Mendelian population are
(i) Population must be sufficiently large.
(ii) Population must have potentialities for free flow of genetic material among individuals, through sexual reproduction,
(iii) Migration should either be nil or negligible.
Class 12 Biology NCERT Exemplar Problems:
The NCERT Exemplar problems are considered to be the most applicative kind of problems which help to enhance a studentтАЩs critical thinking and problem solving ability. These problems form the best practice source to prepare effectively for board exams and the medical entrance tests. So, itтАЩs very important for students to practice the NCERT exemplar problems to prepare well for the boards and the competitive exams.
Main topics discussed in Class 12 Biology, Chapter 7-┬аEvolution, are:
- Origin of life
- Evolution of life forms - a theory
- What are the evidences for evolution?
- Adaptive radiation
- Biological evolution
- Mechanism of evolution
- Hardy - Weinberg principle
- A brief account of evolution
- Origin and evolution of man