With the help of an example, explain how variation leads to evolution.
Some amount of variations are produced even during asexual reproduction but it is very small. The number of variations produced during sexual reproduction is, however, very large. It is due to these variations that no two human beings look alike. The number of successful variations is maximized by the process of sexual reproduction, so we can conclude that the variation is a necessity for organic evolution. Example: Animal reproduced by sexual reproduction show large number of variations.
Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings ?
”The sex of the children is determined by what they inherit from their father and not their mother.” Justify.
Choose the one term from the following which includes the other three :
broccoli, wild cabbage, cauliflower, cabbage
Name five varieties of vegetables which have been produced from ‘wild cabbage’ by the process of artificial selection.
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.
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]
Define the term ‘evolution’. “Evolution cannot be equated with progress”. Justify this statement. [Delhi]
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
Out of bacteria, spider, fish and chimpanzee, which organism has a better body design in evolutionary terms ? Give reason for your answer.
Write the names of at least three inorganic molecules which helped in the origin of life on the earth.
Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.
Give an example of body characteristics used to determine how close two species are in terms of evolution and explain it. [All India]
What is meant by the term speciation? List four factors which could lead to speciation. [Delhi]
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]
Can the wing of butterfly and the wing of a bat be considered homologous organs ? 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 homologous organs? Can the wing of a butterfly and the wing of a bat be regarded as homologous? Why? [All India]
(a) Why did Mendel choose pea plants for conducting his experiments on inheritance ?
(b) State Mendel’s second law of inheritance.
Does geographical isolation of individuals of a species lead to the formation of a new species ? Provide a suitable explanation for your answer.
In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.
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 ?
Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]
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 ?
Name the first scientist who studied the inheritance of traits from one generation to the next.
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.
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.