LAKHMIR SINGH AND MANJIT KAUR Solutions for Class 10 Biology Chapter 4 - Heredity and Evolution
Chapter 4 - Heredity and Evolution Exercise 191
If the trait A exists in 10% of a population of a sexually reproducing species and a trait B exists in 60% of the same population , which trait is likely to have arisen earlier?
Which of the two , sperm or ovum , decides the sex of the child ?
State whether the following statement is true or false :
The sex of an infant is not a case of inheritance of characteristics.
What are the four blood groups in humans?
(b) Turtle (Chrysema Picta)
(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.
(b) Recessive; Dominant.
(c) Free; attached.
(d) 23; 46.
(f) Sex; Female; male.
Chapter 4 - Heredity and Evolution Exercise 192
(b) Dwarf plants: It is dwarf due to the presence of both the recessive genes.
(c) Tall plants: These plants are tall due to the presence of both the dominant genes.
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 ?
(b) Name an animal in which individuals can change sex. What does this indicate?
(b) Snails: This indicates that sex is not determined genetically in some animals.
Explain with an example , how genes control the characteristics (or traits ).
(a) If a sperm carrying X chromosome fertilises an ovum (or egg) which carries X chromosome, then the child born will be a girl. This is because the child will have XX combination of sex chromosomes.
(b) If a sperm carrying Y chromosome fertilises an ovum (or egg) which carries X chromosome, then the child born will be a boy. This is because the child will have XY combination of sex chromosomes.
What do the following symbols used in the topic on heredity represent ?
(a) TT (b) tt (c) XX(d) XY
(b) Dwarf plant.
Pure tall pea plant x Pure dwarf pea plant
(b) Is it an example of monohybrid cross or dihybrid cross?
(b) It is an example of monohybrid cross.
(b) What is the genotype of tall plants which always produced tall offspring?
(c) What is the genotype of (i) dwarf plants, and (ii) tall plants, whose parental cross always produces tall offspring?
(c) (i) tt (ii) TT.
(b)What sizes of plants are produced if both parents have genes Tt?
(b) Three tall plants and one dwarf plant.
(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?
Gregor Mendel's first law of genetics states " Of apair of contrated characters , only one can be represented in agamete by its internal 'factor' .
(a) Give the modern nae for this 'factor'.
(c) State where these factors are found in gametes.
(a) Yellow seed
(b) Round seed
(b) Wrinkled seed: round is dominant: wrinkled is recessive.
(a) What is meant by 'heredity' ? What are the units of heredity .
(b) State Mendel's first law of inheritance.
(b) According to Mendel's first law of inheritance: The characteristics (or traits) of an organism are determined by internal 'factors' which occur in pairs. Only one of a pair of such factors can be present in a single gamete.
Chapter - Exercise
Chapter 4 - Heredity and Evolution Exercise 193
(a) Why did Mendel choose pea plants for conducting his experimentws on inheritance?
(b) State Mendel's second law of inheritance.
(b) According to Mendel's second law of inheritance: In the inheritance of more than one pair of traits in a cross simultaneously, the factors responsible for each pair of traits are distributed independently to the gametes.
(b) Name two human traits which show variation.
(c) how does the creation of variation in a species ensure its survivial?
(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.
(b) What is meant by dominant and recessive genes? Give one example of each.
(c) Explain how, characteristics (or traits) are inherited through genes.
(b) The gene which decides the appearance of an organism even in the presence of an alternative gene is known as dominant gene. The gene which can decide the appearance of an organism only in the presence of another identical gene is called a recessive gene. The dominant gene is represented by a capital letter and the corresponding recessive gene is represented by the corresponding small letter. For example, in pea plants, the dominant gene for tallness is T and the recessive gene for dwarfness is t.
(c) There is a pair of genes for each characteristic of an organism, one is dominant gene and the other is recessive gene. Each parent passes only one of the two genes of the pair for each characteristic to its progeny through gametes. Thus, the male gamete and the female gamete carry one gene for each characteristic from the gene pairs of the parents. When a male gamete fuses with a female gamete during fertilisation they make a new cell called zygote which grows and develops to form a new organism having characteristics from both the parents which it has inherited through genes.
(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?
Mendel then crossed the tall pea plants of the first generation (F1 Generation) and found that tall plants and dwarf plants were obtained in the second generation (or F2 generation) in the ratio of 3:1. Mendel noted that the dwarf trait of the parent pea plant which had seemingly disappeared in the first generation progeny reappeared in the second generation. In this way, Mendel's experiments with tall and dwarf pea plants showed that the traits may be dominant and recessive.
(b) When Mendel crossed pure-bred tall pea plants with pure-bred dwarf pea plants, he found that only tall pea plants were produced in the F1 generation. When Mendel further crossed the tall pea plants of the F1 generation, he found that the tall plants and dwarf plants were obtained in the ratio 3:1 in the F2 generation. Mendel noted that all the pea plants produced in the F2 generation were either tall or dwarf. There were no plants with intermediate height (or medium height) in-between the tall and dwarf plants. In this way, Mendel's experiment showed that the traits (like tallness and dwarfness) are inherited independently. This is because if the traits of tallness and dwarfness had blended (or mixed up), then medium sized pea plants would have been produced.
Chapter 4 - Heredity and Evolution Exercise 208
State whether the following statement is true or false:
Human beings have evoleved from chimpanzees.
Name an animal having rudimentary eyes.
Name tthe ancestor of the following :
Broccoli, Kohlrabi, Kale
Where did life originate on the earth ?
Chapter 4 - Heredity and Evolution Exercise 209
Write the names of at least three inorganic molecules which helped in the origin of life on the earth.
Name two organism which are now extinct and studied from their fossils.
(a) Which two are homologous organs?
(b) Which two are analogous organs?
(b) Wings of birds and wings of insects.
Name five varieties of vaegetables which have been produced from 'wild cabbage' by the process of artificial selection.
broccoli, wild cabbage, cauliflower, cabbage.
(a) The human forelimb and bat's forelimb are an example of ______ organs whereas an insect's wing and a bat's wing are an example of ______ organs.
(b) The evolution of eye is an example of evolution by ______ .
(c) The scientific name of all human beings is ______ .
(d) Broccoli has evolved from _____ by the process of artificial selection.
(e) The theory of natural selection for evolution was proposed by ______ .
(c) Homo sapiens.
(d) Wild Cabbage.
|Column I||Column II|
|(i) Fossil||(a) A famous evolutionist|
|(ii) A theory of evolution||(b) Survival of the fittest|
|(iii) Probabile ancestor of birds||(c) Petrified remains of prehistoric life|
|(iv) Charles Darwin||(d) Father of genetics|
|(v) Gregor Mendel||(e) Archaeoptery x|
(ii) - b.
(iii) - e.
(iv) - a.
(v) - d.
Example - If a beetle does not get sufficient food for a considerable time, its weight will be reduced due to starvation. The low weight of the beetle is an example of acquired trait.
A trait of an organism which is caused by a change in its genes (DNA) is called an inherited trait. Example - The change of colour from red beetle to green beetle is an example of inherited trait.
Can the wing of a butterfly and the wing of a bat be considered homologous organs ? Why or why not ?
In what way are homologous organs evidence for evolution?
Why are the small numbers of surviving tigers acause of worry from the point of view of genetics ?
Will geographical isolation be a major factor in the specification of an organism that reproduces asexually ?
Give reason for your answer .
Out of bacteria , spider, fish and chimpanzee, which organism has a bettr body design in evolutionary terms ? give reason for your answer.
(b) State the various factors which could lead to the formation of new species.
Plant species - Wheat, Paddy, Sunflower etc.
Animal species - Cat, Dog, Tiger, etc.
(b) The important factors which could lead to the rise (or formation) of a new species are the following:
(i) Geographical isolation of a population caused by various types of barriers (such as mountain ranges, rivers and sea). The geographical isolation leads to reproductive isolation due to which there is no flow of genes between separated groups of population.
(ii) Genetic drift caused by drastic changes in the frequencies of particular genes by chance alone.
(iii) Variations caused in individuals due to natural selection.
Chapter 4 - Heredity and Evolution Exercise 210
(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 'extinict' studied?
(a) The theory of origin of life on earth was given by J.B.S Haldane. He suggested in 1929 that life must have developed from the simple inorganic molecules (such as methane, ammonia, hydrogen sulphide, etc.) which were present on the earth soon after it was formed. He said that the conditions on earth at that time (including frequent lightning) could have converted simple inorganic molecules into complex organic molecules which were necessary for life. These complex organic molecules must have joined together to form first primitive living organisms. Haldane also suggested from theoretical considerations that life (or living organisms) originated in the sea water.(b) Those species which are now extinct are studied by studying their fossils which are found during the digging of earth.
Darwin's theory of evolution is known as 'The Theory of Natural Selection'. It can be described as follows:
(i) Within any population there is natural variation. Some individuals have more favourable variations than others.
(ii) Even though all species produce a large number of offspring's, populations remain fairly constant naturally.
(iii) This is due to the struggle between members of the same species and different species for food, space and mate.
(iv) The struggle for survival within populations eliminates the unfit individuals. The fit individuals possessing favourable variations survive and reproduce. This is called natural selection.
(v) The individuals having favourable variations pass on these variations to their progeny from generation to generation.
(vi) These variations when accumulated over a long period of time, lead to the origin of a new species.
(b) In what way are analogous organs evidence for evolution?
Example - wings of a bird and wings of an insect.
Homologous Organ: Organs which have different functions but similar structure and origin.
Example - fore arm of frog, lizard, bird and human.
(b) The presence of analogous organs indicates that even the organisms having organs with different structures can adapt to perform similar functions for their survival under hostile environmental conditions. Thus, the presence of analogous organs in different animals provide evidence for evolution by telling us that though they are not derived from common ancestors, they can still evolve to perform similar functions to survive, flourish and keep on evolving in the prevailing environment.
(b) Will geographical isolation be a major factor in the speciation of a self-pollinating plant species? Give reason for your answer.
The geographical isolation of the two groups of population leads to their reproductive isolation due to which no genes are exchanged between them. However, breeding continues within the isolated populations producing more and more generations. Over the generations, the processes of genetic drift (random change in gene frequency), and natural selection operate in different ways in the two isolated groups of population and make them more and more different from each other. After thousands of years, the individuals of these isolated groups of population become so different that they will be incapable of reproducing with each other even if they happen to meet again. We then say that two new species have been formed.
(b) Geographical isolation will not be a major factor in the speciation of a self pollinating plant because it does not depend on other plants for its process of reproduction to be carried out.
(b) "Only variations that confer an advantage of an individual organism will survive in a population". Do you agree with this statement? Give reason for your answer.
(b) Yes, only those variations that confer advantage to an individual organism will survive in a population. This will become clear from the following example. Suppose there is a population of red beetles in the green bushes and a colour variation arises during reproduction so that one beetle is now green in colour (instead of red). This variation offers advantage of survival because the green beetle can mix up with green bushes, it cannot be spotted and eaten up by a crow and hence its population will increase. If, however, the variation had produced a blue coloured beetle, then this colour could not offer any survival advantage because blue beetle in green bushes could be easily spotted by a crow and eaten by it.
Other Chapters for CBSE Class 10 BiologyChapter 1- Life Processes Chapter 2- Control and Coordination Chapter 3- How do Organisms Reproduce? Chapter 5- Our Environment Chapter 6- Management Of Natural Resources
LAKHMIR SINGH AND MANJIT KAUR Solutions for CBSE Class 10 SubjectsLAKHMIR SINGH AND MANJIT KAUR Solutions for Class 10 Physics LAKHMIR SINGH AND MANJIT KAUR Solutions for Class 10 Chemistry
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