(a) What do you understand by the term ‘variation’ ?
(b) Name two human traits which show variation.
(a) The differences in the characters among the individual of a species is called variation.
(b) Human height and free ear lobe are the traits which show variation in humans.
(c) Due to the creation of variations, a species can adjust to the changing environment around it. And this promotes the survival of the species in the changing environment. Example: The accumulation of ‘heat resistant’ variation (or trait) in some bacteria will ensure its survival even when the temperature in its environment rises too much due to a heat wave or some other reasons. On the other hand, the bacteria which did not have this variation to withstand heat would not survive under these circumstances and die.
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.
Name five varieties of vegetables which have been produced from ‘wild cabbage’ by the process of artificial selection.
Choose the one term from the following which includes the other three :
broccoli, wild cabbage, cauliflower, cabbage
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.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Give reason for your answer.
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.
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]
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 are homologous organs? Can the wing of a butterfly and the wing of a bat be regarded as homologous? Why? [All India]
What is meant by the term speciation? List four factors which could lead to speciation. [Delhi]
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 ?
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 two animals having homologous organs and two having analogous organs. Name these organs.
Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.
Does geographical isolation of individuals of a species lead to the formation of a new species ? Provide a suitable explanation for your answer.
Do genetic combination of mothers play a significant role in determining the sex of new born?
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.
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 ?
What are the different ways in which individuals with a particular trait may increase in a population ?