VSA

1. How do we come know that organisms had common ancestors? (2016)

SA-I

1. Is it necessary that the newly generated species is better than the older one? Explain by giving two points. (2014)

SA-II

1. Variation is useful for the survival of species over time. But the variants have unequal chances of survival. Explain this statement. (2014)
2. Why are variation incorporated at the molecular level significant? (2014)
3. What is the outcome of genetic drift between two sub-populations?
4. Study the given data and answer the questions that follow: (2011)
   1. What is the term given to this type of cross?
   2. What does the data in column 2 indicate? State how did you arrive at this conclusion?

5. Explain with the help of flowchart- “ What determines the sex of a child genetically’? (2011)
6. In human beings, the statistical probability of getting either a male or a female child is 50:50. Give reasons and explain with the help of a diagram. (2012)
7. Sex of the child is determined at the time of conception in human being. Explain this statement. (2015)
8. Explain with the help of a figure that father is responsible for the sex of a child. (2016)
9. Chromosomes are heredity carriers. Why do we say so? (2014)
10. Which vital function is not controlled by autosomes?
11. Homologous organs are different from analogous organs. (2014)
    1. Mention two basic characteristics that decide about analogy and homology between the two organs.
    2. On what basis the classification of organisms into Prokaryotic and Eukaryotic is done?
12. Differentiate between homologous and analogous organs. Give one example of each. (2012)
13. Distinguish between analogous organs and homologous organs. Identify the analogous and homologous organs amongst the following: (2011)

Wings of an insect, wings of a bat, forelimbs of frog, forelimbs of a human.

13. What are fossils? How the life of a fossil is estimated? (2012)
14. All dead organisms do not leave their fossil record, but in some cases, their fossils are formed. How do these fossils records form a direct evidence of past happenings? (2016)
15. Birds and reptiles are closely related. (2015)
    1. Name the connecting link between the two.
    2. Mention two features of each to show that it’s a connecting link between birds and reptiles.
16. An organ like a wing in birds is an advantage to the organism. Did they appear in different stages or were formed due to a single sudden change in them? (2016)

LA

1. Answer the following:
   1. The two cells formed after DNA copying are similar but not identical. What reason can be associated with this? (2016)
   2. Variation though leads to certain changes in an individual but is useful for the survival of species over time. Justify the statement.
   3. Is the consistency of DNA copying important during reproduction?
2. Answer the following:
   1. When a pesticide is sprayed on a population of insects, all insects do not get killed but few of them survive. Give reason. (2014)
   2. When is a recessive trait capable of expressing itself? Write its expression with respect to the height of plant (genotype).
3. From the dihybrid cross shown below answer the following questions. (2014)
   
   1. Write the types of seeds produced in an F1 generation.
   2. Write the types of seeds that were 9,3,3,1 in number respectively.
4. Wings of bats and birds have a different design. (2014)
   1. Explain in which way are they different.
   2. In which aspect do the wings of bat and bird resemble?
5. Give reasons why acquired characters are not inherited. Explain with the help of examples of mice. (2015)
6. What do you understand by the following terms? (2016)
   1. Phenotype
   2. Genotype
   3. Dominant trait
   4. Recessive trait
   5. Factors or genes

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