4. heredity and evolution

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4. heredity and evolution

  1. 1.  We have discussed how some amount of variation is produced even during asexual reproduction. And the number of successful variations are maximised by the process of sexual reproduction.
  2. 2.  The mechanism by which variations are created and inherited. (Heredity). The long-term consequences of the accumulation of variations are also an interesting point to be considered. (Evolution).
  3. 3.  Inheritance from the previous generation provides both a common basic body design, and subtle changes in it, for the next generation.
  4. 4.  The second generation will have differences that they inherit from the first generation. This process continues….
  5. 5.  If there were a population of bacteria living in temperate waters, and if the water temperature were to be increased by global warming, most of these bacteria would die, but the few variants resistant to heat would survive and grow further.
  6. 6.  Some of the variations might be so drastic that the new DNA copy cannot work with the cellular apparatus it inherits. Such a newborn cell will simply die.
  7. 7.  Some DNA copies that would not lead to such a drastic outcome. Surviving cells are similar, but cleverly different from each other. This inbuilt tendency for variation during reproduction is the basis for evolution
  8. 8.  Accumulation of Variation during Reproduction Variation is useful for the survival of species over time.
  9. 9.  Questions NCERT Page No. 143 (Q No. 1 and 2) 1. If a trait A exists in 10% of a population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier? 2. How does the creation of variations in a species promote survival?
  10. 10.  Surviving cells are similar, but cleverly different from each other.
  11. 11.  The process by which traits and characteristics are reliably inherited from the parents to offspring. A trait is a particular characteristic— anatomical, biochemical or behavioural—that is the result of gene–environment interaction.
  12. 12.  Free and attached earlobes are two variants found in human populations.
  13. 13.  This means that each trait can be influenced by both paternal and maternal DNA. Thus, in each child, for each trait there will be two versions (Allele), one inherited from each parent.
  14. 14.  An allele is two or more forms of the DNA sequence of a particular gene.There are two types-- Heterozygous – If the two alleles for a trait are different (Tt) Homozygous – If the two alleles for a trait are the same (TT)
  15. 15.  Mendel blended his knowledge of science and mathematics and was the first one to keep count of individuals exhibiting a particular trait in each generation. This helped him to arrive at the laws of inheritance
  16. 16.  The rules of heredity determine the process by which traits and characteristics are reliably inherited. The rules of heredity determine the process by which traits and characteristics are reliably inherited.
  17. 17.  Read NCERT Page No. 142-146 Write a brief biography of Gregor Johann Mendel (1822–1884)
  18. 18.  The process by which traits and characteristics are reliably inherited from the parents to offspring.
  19. 19.  This means that each trait can be influenced by both paternal and maternal DNA. Thus, for each trait there will be two versions in each child.
  20. 20.  Mendel took pea plants with Parent (P) different characteristics – a tall plant and a short plant,TT (Tall) tt (Short)
  21. 21. TT (Tall) tt (Short) Linkage of two genes located on same chromosome T t Tt (all)First Generation (F1)
  22. 22.  The progeny of the TT X TT parental plants were, of course, all tall.TT (all are tall)
  23. 23. Tt X TtFirst Generation F1 X F1 ?
  24. 24. Tt X Tt SpermFirst Generation T t F1 X F1 T Since both the genes are carried on the sane chromosome they do not separate from each other at Egg meiosis, F1 Progeny produces only t two types of gametes.
  25. 25. Tt X TtFirst Generation F1 X F1 T Sperm t TT Tt T Tall Tall EggSecond Generation Tt tt t Tall Short (F2)
  26. 26. Phenotype - the way an organism looks, Examples: Tall or ShortGenotype - the gene combination of an organism, Ex:- TT, Tt, tt TT Tt Tall Tall Tt tt Tall Short
  27. 27.  Were the tall plants in the Tt (all) F1 generation exactly theFirst Generation (F1) same as the tall plants of the parent generation?
  28. 28. Tt (all)  But only the tallness trait was expressed in F1.First Generation (F1)  These two may be identical, or may be different, depending on the parentage.
  29. 29.  The trait that is observed in the offspring is the dominant trait (uppercase)TT Tt  Traits like ‘T’ are called dominant traits,  The trait that disappears in theTt tt offspring is the recessive trait (lowercase)  While those that behave like ‘t’ are called recessive traits.
  30. 30.  Rules for the Inheritance of Traits (Incase of single trait) In the F1 Progeny all were tall plants In the F2 Progeny all were not tall (ratio 3:1)
  31. 31. Questions NCERT Page No. 147 (Q No. 1), Page 1441. How do Mendel’s experiments show that traits may be dominant or recessive? Explain with diagram.2. What experiment would we do to confirm that the F2 generation did in fact have a 1:2:1 ratio of TT, Tt and tt trait combinations?
  32. 32. TT (Tall) tt (Short) T t  Were the tall plants in the F1 Tt (all) generation exactly the same asFirst Generation (F1) the tall plants of the parent generation?
  33. 33. Tt X TtFirst Generation F1 X F1 T Sperm t TT Tt T Tall Tall EggSecond Generation Tt tt t Tall Short (F2)
  34. 34.  The trait that is observed in the offspring is the dominant trait (uppercase)TT Tt  Traits like ‘T’ are called dominant traits,  The trait that disappears in theTt tt offspring is the recessive trait (lowercase)  While those that behave like ‘t’ are called recessive traits.
  35. 35. Parent (P)Round: R Wrinkled: rGreen: y Yellow: Y
  36. 36. Segregation of twohypothetical geneslocated on differentchromosome
  37. 37. Sperm RY Ry rY ry RY Ry Since the chromosomes segregate independently at meiosis, the F1 Progeny give rise to four different rY types of gametes.Egg ry
  38. 38. Sperm RY Ry rY ry Round Yellow Round Yellow Round Yellow Round Yellow RY RRYY RRYy RrYY RrYy Round Yellow Round Green Round Yellow Round Green Ry RRYy RRyy RrYy Rryy Round Yellow Round Yellow Wrinkled Yellow Wrinkled Yellow rY RrYY RrYy rrYY rrYyEgg Wrinkled Yellow Wrinkled Green Round Yellow Round Green ry RrYy Rryy rrYy rryy
  39. 39. Find Genotypic Ratio RY Ry rY ry--------------------------- Round Yellow Round Yellow Round Yellow Round Yellow RY RRYY RRYy RrYY RrYy Round Yellow Round Green Round Yellow Round Green Ry RRYy RRyy RrYy Rryy Round Yellow Round Yellow Wrinkled Yellow Wrinkled Yellow rY RrYY RrYy rrYY rrYy Round Yellow Round Green Wrinkled Yellow Wrinkled Green ry RrYy Rryy rrYy rryy
  40. 40.  Rules for the Inheritance of Traits (Incase of dual traits) In the F1 Progeny all were Round, Yellow In the F2 Progeny Ratio (9:3:3:1)
  41. 41. Questions NCERT Page No. 147 (Q No. 2 and 3)1. How do Mendel’s experiments show that traits areinherited independently?2. A man with blood group A marries a woman with bloodgroup O and their daughter has blood group O. Is thisinformation enough to tell you which of the traits – bloodgroup A or O – is dominant? Why or why not?
  42. 42.  The process by which traits and characteristics are reliably inherited from the parents to offspring.
  43. 43.  This means that each trait can be influenced by both paternal and maternal DNA. Thus, for each trait there will be two versions in each child.
  44. 44. Tt X TtFirst Generation F1 X F1 T Sperm t TT Tt T Tall Tall EggSecond Generation Tt tt t Tall Short (F2)
  45. 45. Sperm RY Ry rY ry Round Yellow Round Yellow Round Yellow Round Yellow RY RRYY RRYy RrYY RrYy Round Yellow Round Green Round Yellow Round Green Ry RRYy RRyy RrYy Rryy Round Yellow Round Yellow Wrinkled Yellow Wrinkled Yellow rY RrYY RrYy rrYY rrYyEgg Wrinkled Yellow Wrinkled Green Round Yellow Round Green ry RrYy Rryy rrYy rryy
  46. 46. Round Yellow Round Yellow Round Yellow Round Yellow RRYY RRYy RrYY RrYyTT Tt Round Yellow RRYy Round Green RRyy Round Yellow RrYy Round Green RryyTt tt Round Yellow Round Yellow Wrinkled Yellow Wrinkled Yellow RrYY RrYy rrYY rrYy Round Yellow Round Green Wrinkled Yellow Wrinkled Green RrYy Rryy rrYy rryy
  47. 47.  Cellular DNA is the information source for making proteins in the cell. A section of DNA that provides information for one protein is called the gene for that protein.
  48. 48. More efficient Less efficientenzyme / Protein enzyme / Protein MoreHormone ? Less Hormone Taller Shorter
  49. 49. More efficient Less efficientenzyme / Protein enzyme / Protein MoreHormone G Less Hormone Taller Shorter
  50. 50.  This means that each pea plant must have two sets of all genes (Allele), one inherited from each parent. An allele is two or more forms of the DNA sequence of a particular gene.
  51. 51.  Each gene set is present in the body cell as separate independent pieces, each called a chromosome. Thus, each cell will have two copies of each chromosome, one each from the male and female parents. Every germ cell will take one chromosome from each pair and these may be of either maternal or paternal origin. When two germ cells combine, they will restore the normal number of chromosomes in the progeny, ensuring the stability of the DNA of the species.
  52. 52.  They reproduce sexually They have two distinct, male and female, sex cells called gametes Their traits are easy to isolate. They can be crossed easily.
  53. 53.  A section of DNA that provides information for one protein is called the gene for that protein. In the Mendelian experiments both parents must be contributing equally. Formation of single set of genes by the each germ cell Selection of pea plants.
  54. 54. Read NCERT Page No. 142 to 146
  55. 55.  The two alleles for a trait must separate when gametes are formed A parent randomly passes only one allele for each trait to each offspring
  56. 56.  The genes for different traits are inherited independently of each other.
  57. 57. Factors of temperature Change of sex.Factors of inherited sex chromosome
  58. 58. Normal Human Chromosome, Total 23 pairs (46) Paternal Copy Maternal Copy 22 pairs of Autosomes (44)1 pair Sex Chromosome (XY) 1 pair Sex Chromosome (XY) Male Female
  59. 59.  A child who inherits an X chromosome from her father will be a girl, and one who inherits a Y chromosome from him will be a boy. Thus a father is responsible for giving birth of a boy or a girl, not mother.
  60. 60.  The human sperm cell is haploid.
  61. 61.  The human ovum cell is also haploid.
  62. 62.  The two alleles for a trait must separate when gametes are formed The genes for different traits are inherited independently of each other. Sex determination in human
  63. 63. Questions NCERT Page No. 147 (Q No. 4)4. How is the sex of the child determined in human beingswith diagram?
  64. 64.  We learnt that the chromosomes in the nucleus of a cell contain information for inheritance of features from parents to next generation in the form of DNA
  65. 65.  If the information is changed, different proteins will be made. Different proteins will eventually lead to altered body designs.
  66. 66. More efficient Less efficientenzyme / Protein enzyme / Protein MoreHormone G Less Hormone Taller Shorter
  67. 67.  This creates two copies of the DNA in a reproducing cell, and they will need to be separated from each other.
  68. 68.  DNA copies separate, each with its own cellular apparatus. Effectively, a cell divides to give rise to two cells.
  69. 69.  The DNA copies generated will be similar, but may not be identical to the original. This inbuilt tendency for variation during reproduction is the basis for evolution.
  70. 70. Analyse variations in the red beetles population Situation 1 Situation 2 Situation 3
  71. 71. Frequency of certain genes in a population changed over generations. natural selection is directingSituation 1 evolution in the beetle population. It results in adaptations in the beetle population. Accidents in small populations can change the frequency of some genes in a population, even if theySituation 2 give no survival advantage. It provides diversity without any adaptations. Changes in body without any genetic variations, due to environmental factors, but it is not evolution. Changes in theSituation 3 non-reproductive tissues caused by environmental factors are not inheritable.
  72. 72.  A basic event in reproduction is the creation of a DNA copy which bring variation. Variation may be by survival due to natural selection, may be accidental or may be due to environmental situations
  73. 73. Read NCERT Page No. 147-148
  74. 74.  The DNA copies generated will be similar, but may not be identical to the original. This inbuilt tendency for variation during reproduction is the basis for evolution.
  75. 75. Variations in the red beetles population Situation 1 Situation 2 Situation 3
  76. 76.  Changes in the non- reproductive tissues caused by environmental factors are not inheritable.  Changes in the body without any genetic variations, due to environmental factors, but it is not evolution.Situation 3
  77. 77. ACQUIRED TRAITS INHERITED TRAITS These are those characters,  These are those characters, received by an organism in received by an organism his/her life time due to from his/ her ancestors different conditions. through GENES. Ex:- Due to an accident a  Ex:- Tall and Short height, man had lost his leg, Attack Eye colour, skin colour, of Polio. body structure, general characters etc.
  78. 78.  When change in reproductive tissues pass (as a new trait) on to the progeny (DNA of the germ cells), evolutions come.
  79. 79.  If we breed a group of mice, all their progeny will have tails, as expected. Now, if the tails of these mice are removed by surgery in each generation, do these tailless mice have tailless progeny?
  80. 80.  It makes sense because removal of the tail (acquired trait) cannot change the genes of the germ cells of the mice. Acquired trait can not pass on to the next generation. So, it is important to inherit GENES to bring evolution.
  81. 81.  This is the reason why the ideas of heredity and genetics that we have discussed earlier are so essential for understanding evolution.
  82. 82.  Darwin formulated his hypothesis that evolution took place due to natural selection. But he did not know the mechanism whereby variations arose in the species.
  83. 83.  Evolution is the change in the inherited traits of a population of organisms through successive generations. This change results from interactions between processes that introduce variation into a population.
  84. 84. Mendel’s experiments give usthe mechanism for theinheritance of traits from onegeneration to the next. Darwin’s theory of evolution tells us how life evolved from simple to more complex forms.
  85. 85. Formation of EarthSimple Inorganic moleculesSimple organic moleculesComplex organic molecules
  86. 86. Artificial atmosphere, NH3, CH4, H2S (No O2) over water Bellow 100 o C , Electrical sparks-lightning 15% of Carbon (C) from Methane get convertedSimple organic molecules Amino Acids- Protein Formation of Protoplasm Simple Cell
  87. 87.  Acquired and Inherited Traits Changes in the specialised reproductive tissues of germ cells bring variation. Evolution comes with inheritance. Origin of life.
  88. 88. Read NCERT Page 149-150, NCERT Exercise Q No. 1,2,3 (Page 149)1. What are the different ways in which individuals with a particular trait may increase in a population?2. Why are traits acquired during the life-time of an individual not inherited?3. Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics?
  89. 89. Variations in the red beetles population Situation 1 Situation 2 Situation 3
  90. 90.  But this does not properly explain formation of new species.
  91. 91. Both they belong to the same population, so here speciation does not occur.
  92. 92. Genetic flow in each sub-population brings variationsNatural selection in each sub-populationVariation is combined with geographical isolation, thenChange in the DNA & number of chromosomes, thusGerm cells of the two groups cannot fuse with each other.
  93. 93.  Characteristics are details of appearance or behaviour; in other words, a particular form or a particular function.
  94. 94. CellProkaryotic EukaryoticUnicellular Unicellular Multicellular Monera Protista Fungi Planate Animalia
  95. 95.  We can thus build up small groups of species with recent common ancestors.A common ancestor
  96. 96.  Tracing common ancestors back in time leads us to the idea that at some point of time, non-living material must have given rise to life.
  97. 97.  Speciation-Formation of new species. Characteristics are details of appearance or behaviour; in other words, a particular form or a particular function. The more characteristics two species will have in common, the more closely they are related. A hierarchy is developing that allows us to make classification groups
  98. 98. Read NCERT Page 150-152, NCERT Exercise Q No. 1,2,3 (Page 151)1. What factors could lead to the rise of a new species?2. Will geographical isolation be a major factor in the peciation of aself pollinating plant species? Why or why not?3. Will geographical isolation be a major factor in the speciation ofan organism that reproduces asexually? Why or why not?
  99. 99. Genetic flow in each sub-population brings variationsNatural selection in each sub-populationVariation is combined with geographical isolation, thenChange in the DNA & number of chromosomes, thusGerm cells of the two groups cannot fuse with each other.
  100. 100. CellProkaryotic EukaryoticUnicellular Unicellular Multicellular Monera Protista Fungi Planate Animalia
  101. 101. A common ancestor
  102. 102.  Excavating and Time-dating Studying fossils, Determining DNA sequences
  103. 103.  Characteristics in different species would be similar because they are inherited from a common ancestor. It is known as homologous characters.
  104. 104.  Characteristics in different species would be different in body design but have a common look and truly derived from two different ancestors. It is known as analogous characters.
  105. 105.  Fossils are the preserved remains of animals, plants, and other organisms from the remote past. The fossil record is life’s evolutionary epic that unfolded over four billion years as environmental conditions and genetic potential interacted in accordance with natural selection.
  106. 106.  Digging the soil and finding layers of soil and rock particles. By detecting the ratios of different isotopes of the same element in the fossil material.
  107. 107.  Homologous characters Analogous characters. Fossils are the preserved remains of animals, plants, and other organisms from the remote past
  108. 108. Read NCERT Page 153-155, NCERT Exercise Q No. 2,3 (Page 156)2. Can the wing of a butterfly and the wing of a bat beconsidered homologous organs? Why or why not?3. What are fossils? What do they tell us about the process ofevolution?Extra Question: Explain the formation of fossils.
  109. 109.  Characteristics in different species would be similar because they are inherited from a common ancestor. It is known as homologous characters.
  110. 110.  Characteristics in different species would be different in body design but have a common look and truly derived from two different ancestors. It is known as analogous characters.
  111. 111.  Fossils are the preserved remains of animals, plants, and other organisms from the remote past.
  112. 112.  The fossil record is life’s evolutionary epic that unfolded over four billion years as environmental conditions and genetic potential interacted in accordance with natural selection.
  113. 113.  Complex organs may have evolved because of the survival advantage of even the intermediate stages. Organs or features may be adapted to new functions during the course of evolution.
  114. 114.  For example, feathers are thought to have been initially evolved for warmth and later adapted for flight.
  115. 115.  If that is the case, then comparing the DNA of different species should give us a direct estimate of how much the DNA has changed during the formation of these species.
  116. 116.  Complex organs may have evolved because of the survival advantage of even the intermediate stages. Organs or features may be adapted to new functions during the course of evolution. Changes in DNA during reproduction are the basic events in evolution
  117. 117. Read NCERT Page 153-155, NCERT Exercise Q No. 1 (Page 156)Give an example of characteristics being used to determine howclose two species are in evolutionary terms.Extra Question: Write a short note on Molecular phylogeny.
  118. 118.  For example, feathers are thought to have been initially evolved for warmth and later adapted for flight.
  119. 119.  If that is the case, then comparing the DNA of different species should give us a direct estimate of how much the DNA has changed during the formation of these species.
  120. 120.  Evolution cannot be said to ‘progress’ from ‘lower’ forms to ‘higher’ forms. Rather, evolution seems to have given rise to more complex body designs even while the simpler body designs continue to flourish.
  121. 121.  A new species has emerged. It will all depend on the environment. It is just that natural selection and genetic drift have together led to the formation of a population that cannot reproduce with the original one.
  122. 122.  Rather, both human beings and chimpanzees have a common ancestor a long time ago. That common ancestor is likely to have been neither human or chimpanzee. Instead, the two resultant species have probably evolved in their own separate ways to give rise to the current forms.
  123. 123.  There is no biological basis to the notion of human races. Study of the evolution of human beings indicates that all of us belong to a single species that evolved in Africa and spread across the world in stages.
  124. 124.  EVOLUTION SHOULD NOT BE EQUATED WITH ‘PROGRESS’ Human Evaluation
  125. 125. Read NCERT Page 156-158, NCERT Exercise Q No. 1, 2 (Page 158)NCERT Exercise Q No. 1 to 12 (Page 159)

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