Explain with an example, how genes control the characteristics (or traits).
The characteristics or traits in animals and plants are controlled by genes. For example the transmission of color of hair from the parents to the child. If a mother has black hair and the father has blonde hair and the child has black hair then the transmission of genes for hair colour from the mother and father to the child is as follows: Mother’s cell contains two genes HH for black hair. Both the genes HH are dominant genes, so the mother has black hair. Father’s cell contains two genes (hh) for blonde hair. The two genes hh are recessive genes, so the father has blonde hair. Now, during the process of reproduction, the mother transmits one of the dominant genes H for black hair to the child and the father transmits one of his recessive genes h for blonde hair to the child. Due to this, the child has the genes Hh for her hair. Now the gene H for black hair is the dominant gene but the gene h for blonde hair is the recessive gene. The dominant gene H for black hair shows its effect due to which the child has black hair.
What is a gene?
A man having blood group O marries a woman having blood group B and they have a daughter. What will be the blood group of the daughter ?
Name the scientist who gave the theory of evolution.
Why are traits acquired during the lifetime of an individual not inherited ?
Who provided the evidence of DNA as the genetic material? Write the names of the components of the DNA molecule.
Describe briefly four ways in which individuals with a particular trait may increase in a population. [Foreign]
Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings ?
If the 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 ?
What type of plants were used by Mendel for conducting his experiments on inheritance ?
Gregor Mendel’s first law of genetics states “Of a pair of contrasted characters, only one can be represented in a gamete by its internal ‘factor’.
(a) Give the modern name for this ‘factor’.
(b) State where these factors are found in gametes.
(a) How do Mendel’s experiments show that traits may be dominant or recessive ?
(b) How do Mendel’s experiments show that traits are inherited independently ?
What are fossils ? Giving one example, explain how fossils provide evidence for evolution.
Does geographical isolation of individuals of a species lead to the formation of a new species ? Provide a suitable explanation for your answer.
(a) Define ‘natural selection’.
(b) “Only variations that confer an advantage to an individual organism will survive in a population”. Do you agree with this statement ? Give reason for your answer.
Mention three important features of fossils which help in the study of evolution.
In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.
Explain how sexual reproduction gives rise to more viable variations that asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ?
Define evolution. Describe the contribution of Lamarck.
State whether the following statement is true or false :
The sex of an infant is not a case of inheritance of characteristics.
Which of the following represent tall plants and which represent short plants (or dwarf plants) ?Which of the following represent tall plants and which represent short plants (or dwarf plants) ?
Give reason for your choice (The symbols have their usual meaning).
In a human, how many chromosmes are present in :
(a) a brain cell ?
(b) a sperm in the testes ?
(c) an egg which has just been produced by the ovary ?
(d) a skin cell ?
(e) a fertilised egg ?
What name is given to the sequence of gradual changes over millions of years in which new species are produced ?
Write the names of at least three inorganic molecules which helped in the origin of life on the earth.
What evidence do we have for the origin of life from inanimate matter (lifeless matter) ?
Bacteria have a simpler body plan when compared with human beings. Does it mean that human beings are more evolved than bacteria? Provide a suitable explanation.
What are the different ways in which individuals with a particular trait may increase in a population ?
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?
Can the wing of butterfly and the wing of a bat be considered homologous organs ? Why or why not ?
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
Explain the importance of fossils in deciding evolutionary relationships.
What evidence do we have for the origin of life from inanimate matter?
Name the plant on which Mendel performed his experiments.
What is a sex chromosome?
Define homologous organs.
Where are the genes located? What is the chemical nature of genes?
Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]
What are fossils? What do they tell us about the process of evolution? [All India(C): All India 2011]
Distinguish between acquired and inherited traits by giving one example of each. Why are traits acquired during the lifetime of an individual not inherited? [Delhi(C)]
What constitutes the link between one generation and the next ?
Which of the two, sperm or ovum, decides the sex of the child ?
Name the famous book written by Charles Robert Darwin.
Name five varieties of vegetables which have been produced from ‘wild cabbage’ by the process of artificial selection.
What is meant by acquired and inherited traits ? Explain with one example each.
Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.
With the help of an example, explain how variation leads to evolution.
Does geographical isolation of individual of a species lead to formation of a new species? Provide a suitable explanation.
A man with blood group A marries a woman with blood O and their daughter has blood group O. Is this information enough to tell you which of the traits blood group A or O is dominant ? Why or why not ?
Give an example of characteristics being used to determine how close two species am in evolutionary terms ?
Why are human beings who look so different from each other in terms of size, colour and looks said to belong to the same species ?