Define a gene.
A gene is a small portion of the DNA, with codes for a particular polypeptide or a protein. In other words, it is the functional unit of the DNA. It is also responsible for the transmission of hereditary characters from the parents to the offspring.
Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.
What is meant by the term speciation? List four factors which could lead to speciation. [Delhi]
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?
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 do the following symbols used in the topic on heredity represent ?
(a) TT
(b) tt
(c) XX
(d) XY
(a) If a normal human cell has 46 chromosomes, how many chromosomes will be there in a human (;) sperm cell, and (ii) zygote ?
(b) What sizes of plants are produced if both parents have genes Tt ?
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 ?
(a) What do you understand by the term ‘variation’ ?
(b) Name two human traits which show variation.
Name two animals having homologous organs and two having analogous organs. Name these organs.
a) Name the scientist who gave the theory of origin of life on earth. What is this theory ?
(b) How are those species which are now ‘extinct’ studied ?
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]
State the meaning of inherited traits and acquired traits. Which of the two is not passed on to the next generation? Explain with the help of an example.
The gene for red hair is recessive to the gene for black hair. What will be the hair colour of a person if he inherits a gene for red hair from his mother and a gene for black hair from his father ?
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.
Give the contrasting traits of the following characters in pea plant and mention which is dominant and which is recessive :
(a) Yellow seed (b) Round seed
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 ?
(a) What is meant by a species ? Give two examples of plant species and two of animals.
(b) State the various factors which could lead to the formation of new species.
A woman has only daughters. Analyse the situation genetically and provide a suitable explanation.
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.
Evolution has exhibited a greater stability of molecular structure when compared with morphological structures. Comment on the statement and justify your opinion.
Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?
During which stage can the chromosomes be seen clearly? Write the features of the eukaryotic and prokaryotic chromosomes.
Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]
Describe briefly four ways in which individuals with a particular trait may increase in a population. [Foreign]
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)]
The human beings who look so different from each other in terms of colour, size and looks are said to belong to the same species. Why? Justify your answer. [All India(C)]
Give one example each of characters that are inherited and the ones that are acquired in humans. Mention the difference between the inherited and the acquired characters. [Delhi]
How is the equal genetic contribution of male and female parents ensured in the progeny? [Delhi]
Explain with examples how the following are evidences in favour of evolution in organisms. (i) Homologous organs (ii) Analogous organs (iii) Fossils [Delhi]