Biblical Calendar of History
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Biblical Calendar of History


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  • expression écrite
A Chronological Record of Events According to the Holy Bible
  • creation of adam 11013 b.c. seth
  • amram 137 years
  • kohath 133 years
  • seth
  • amram
  • kohath
  • levi
  • thirty years
  • levi 77 years
  • calendar



Publié par
Nombre de lectures 10
Langue English
 BALBHARATI PUBLIC SCHOOL, PITAMPURA  CLASSX, SUBBIOLOGY  COREASSSGHEREDITY AND EVOLUTION  TERM II Q1. How do Mendel’s experiments show that traits may be dominant or recessive? Ans1Mendel crossed Garden Pea plants having contrasting visible traits e.g., tall and dwarf, Violet and white flowered. In F1 generation there were no halfway characteristics. A cross between pure tall and pure dwarf plants yields only tall plants in F1 generation. There were no medium height plants. When F1 plants were self bred, the F2 were not all tall plants. Instead, both tall and dwarf plants appeared in the ratio of 3:1.It means that the trait for dwarfness was present in F1 generation but was not expressed while the trait for tallness expressed itself. The trait which expresses itself is called dominantand the other trait unable to express its effect in the presence of its contrasting trait is known asrecessive.
Q2. How is the sex of a baby determined in human beings?
Ans 2Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs. But one pair, called the sex chromosomes, is odd in not always being a perfect pair. Women have a perfect pair of sex chromosomes, both called X. But men have a mismatched pair in which one is a normalsized X while the other is a short one called Y. So women are XX, while men are XY. All children will inherit an X chromosome from their mother regardless of whether they are boys or girls. Thus, the sex of the children will be determined by what they inherit from their father. 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.
Q3 How do Mendel’s experiments show that traits are inherited independently? Ans3 Mendel crossed pure breeding tall plants having round seeds with pure breeding short plants having wrinkled seeds. The plants of F1 generation were all tall with round seeds indicating that the traits of tallness and round seeds were dominant. Self breeding of F1 yielded plants with characters of 9 tall round seeded, 3 tall wrinkled seeded , 3 short round seeded and one short wrinkled seeded. Tall wrinkled seeded and short round seeded plants are new combinations which can develop only when the traits are inherited independently. Q4) Define evolution.
Ans4it a slow gradual process which occurs due to cumulative effects of adaptations and helps it to survive in a better way.
Q5) How are fossils helpful in developing evolutionary relationships?
Ans5fossils form a connecting link between groups of organisms.
Q6) Cat’s paw, human hand and horse’s legsare these organs homologous or analogous? Give reason
Ans6they are homologous organs as they are of same origin performing different functions.
Q7) Wings of bird and wings of insectare these organs homologous or analogous? Give one suitable reason to support your answer.
Ans7they are analogous organs as both have developed from different origin and perform same function of flying.
Q8) Give one difference between eyes and eye spot. Which animal possesses eye spots?
Ans8eyes are well developed organs helping to form an image, but eye spots just enable the animal to distinguish between day light and darkness.e.g. planaria and euglena possess eye spots
Q9) give one difference between artificial selection and natural selection.
ANS9Artificial selection is that in which man selects the beneficial gene and modifies it according to his requirement whereas in natural selection nature selects the advantageous gene and helps it to multiply.
Q10) What is true humans have evolved from chimpanzees or humans and chimpanzees both have evolved from a common ancestor?
Ans10Both have evolved from a common ancestor because both are existing today .man has not replaced chimpanzees.
Q11) Whatis the mechanism behind the expression of a particular trait? Explain briefly.
Ans11the mechanism behind the expression of trait is the presence of a functional gene. When gene is functional it is capable of producing a hormone or enzyme which helps in expression of that trait. But sometimes genes get altered and become nonfunctional, then the enzyme is not produced and the trait does not get expressed.
Q12) What will happen to the expression of a particular trait if a gene gets altered?
Ans12when gene gets altered the corresponding enzyme is not produced, hence the hormone related to it is not produced and the particular trait does not expressed. there are chances that instead a disease maybe seen due to altered gene
.Q13) What are various ways by which genes can enter a population?
Ans13) the various ways are
a) GENE MIGRATION is gene flow which occurs when some members of main population migrate to other areasand may not comeback .this is geographical isolation.
b) GENETIC DRIFTis change in gene frequency due to chance or accident and not by natural selection.
c) NATURAL SELECTIONis a process in which better quality genes selected by nature are allowed to multiply.
d)MUTATIONS arise suddenly they are sudden changes in the gene inherited by off springs for atleast 46 generations.
Q14) How will new species arise in case:
a) two subpopulations are separated due to a huge mountain in between them?
b)a small population of individuals gets drifted away from the main land due to sea?
Ans14new species will arise;
a)the huge mountain acts as a geographical barrier and the members of the two subpopulation will not be able to mate with one another due to this mountain .this will keep mating within the members of their own subpopulation and hence two new species will arise.
b)when the small population gets drifted away from main land by sea,here also chances are that there may be some kind of gene flow between the partly separated populations, but if the two populations do not meet, chances are that two new species would arise.
Q15) Only advantageous variations help in the evolution of an organism giving rise to a new species.expalin with the help of an example. Ans15this is because the advantageous variations are selected by nature and allowed to multiply or propagate fast to increase their members. because such variations help an individual to survive in a better manner in changing environment the population increases. this can be explained as under; A_EVOLUTION OF EYE which has occurred bit by bit and not in one step. Even the rudimentary eye was advantageous to Planaria or Octopus even though a clear image was not formed as in humans still it gave a fitness advantage. B_EVOLUTION OF WINGearlier feathers were formed to provide warmth to the body, later these feathers helped in flying.