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.
Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings ?
Choose the one term from the following which includes the other three :
broccoli, wild cabbage, cauliflower, cabbage
”The sex of the children is determined by what they inherit from their father and not their mother.” Justify.
Name five varieties of vegetables which have been produced from ‘wild cabbage’ by the process of artificial selection.
Explain the mechanism of sex determination in humans. [All India]
Or
With the help of a flow chart explain in brief how the sex of a newborn is genetically determined in human beings. Which of the two parents, the mother or the father, is responsible for determination of sex of a child? [Foreign]
State one characteristic which shows that the birds are very closely related to dinosaurs.
What type of plants were used by Mendel for conducting his experiments on inheritance ?
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Give reason for your answer.
An individual cannot pass on to its progeny the experiences of its lifetime.” Justify the statement with the help of an example and also give reason for the same. [Foreign]
Study the following cross and showing self-pollination in Flf fill in the blank and answer the question that follows
Define the term ‘evolution’. “Evolution cannot be equated with progress”. Justify this statement. [Delhi]
Write the names of at least three inorganic molecules which helped in the origin of life on the earth.
What are homologous organs? Can the wing of a butterfly and the wing of a bat be regarded as homologous? Why? [All India]
Does geographical isolation of individuals of a species lead to the formation of a new species ? Provide a suitable explanation for your answer.
If we cross pure-bred tall (dominant) pea plant with pure-bred dwarf (recessive) pea plant we will get pea plants of F1 generation. If we now self-cross the pea plant of F2 generation, then we obtain pea plants of F2 generation.
(a) What do the plants of F2 generation look like?
(b) State the ratio of tall plants to dwarf plants in F2 generation.
(c) State the type of plants not found in F2 generation but appeared in F2 generation, mentioning the reason for the same. [All India]
Fill in the following blanks with suitable words :Fill in the following blanks with suitable words :
(a) Genes always work in …………………
(b) In pea plants, the gene for dwarfness is………………… whereas that for tallness is…………………
(c) Most people have………………… earlobes but some have………………… earlobes.
(d) A human gamete contains………………… chromosomes whereas a normal body cell has………………… chromosomes in it.
(e) All races of man have………………… blood groups.
(f) The………………… chromosomes for a………………… are XX whereas that for a………………… are XY.
Out of bacteria, spider, fish and chimpanzee, which organism has a better body design in evolutionary terms ? Give reason for your answer.
In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.
Does geographical isolation of individual of a species lead to formation of a new species? Provide a suitable explanation.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?
In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better body design’ why or why not ?
What are fossils? What do they tell us about the process of evolution? [All India(C): All India 2011]
Mendel said that the characteristics or traits of organisms are carried from one generation to the next by internal factors which occur in pairs. What is the modern name for these factors ?
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 ?
(a) State one advantage of variation to a species.
(b) What are sex chromosomes ? How many sex chromosomes are there ? Name them.
State whether the following statement is true or false :
Human beings have evolved from chimpanzees.
What are fossils ? Giving one example, explain how fossils provide evidence for evolution.
Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.
(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.
Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.