Biology

Heredity and Evolution

Question:

Explain how sexual reproduction gives rise to more viable variations that asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ?

Answer:

Variations occurring during sexual reproduction may be due to:
(i) Separation of homologous chromosomes (by chance only) during gamete formation.
(ii) Crossing over (recombination) of homologous chromosomes.
(iii) Fertilisation of gametes to form zygote.
(iv) Errors during DNA copying or mutations. In asexually reproducing organisms only errors during DNA copying or mutations cause variations.
Since the extent of variations is much larger in sexually reproducing organisms, therefore, the chances of evolution is also much in sexually reproducing These variations enable the organisms to adapt themselves to the changing conditions and also help to face the struggle for Over the time, they and rise to new species.

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Heredity and Evolution

Q 1.

Which of the processes, sexual reproduction or asexual reproduction, brings about maximum variations in the offsprings ?

Q 2.

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 ?

Q 3.

Name the scientist who gave the theory of evolution.

Q 4.

What are fossils? What do they tell us about the process of evolution? [All India(C): All India 2011]

Q 5.

Gregor Mendel’s first law of genetics states “Of a pair of contrasted characters, only one can be represented in a gamete by its internal ‘factor’.
(a) Give the modern name for this ‘factor’.
(b) State where these factors are found in gametes.

Q 6.

Why are traits acquired during the lifetime of an individual not inherited ?

Q 7.

During which stage can the chromosomes be seen clearly? Write the features of the eukaryotic and prokaryotic chromosomes.

Q 8.

What is a gene?

Q 9.

Describe briefly four ways in which individuals with a particular trait may increase in a population. [Foreign]

Q 10.

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]

Q 11.

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 ?

Q 12.

Which of the following represent tall plants and which represent short plants (or dwarf plants) ?Which of the following represent tall plants and which represent short plants (or dwarf plants) ?
(a) Tt
(b) tt
(c) TT
Give reason for your choice (The symbols have their usual meaning).

Q 13.

(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 ?

Q 14.

Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Give reason for your answer.

Q 15.

What evidence do we have for the origin of life from inanimate matter (lifeless matter) ?

Q 16.

Does geographical isolation of individuals of a species lead to the formation of a new species ? Provide a suitable explanation for your answer.

Q 17.

In human beings, the statistical probability of getting either a male or female child is 50 : 50. Give a suitable explanation.

Q 18.

What are homologous structures? Give an example. Is it necessary that homologous structures always have a common ancestor?

Q 19.

What are the different ways in which individuals with a particular trait may increase in a population ?

Q 20.

How are the areas of study – evolution and classification inteilinked?

Q 21.

What evidence do we have for the origin of life from inanimate matter?

Q 22.

What is heredity?

Q 23.

Write the expanded form of DNA.

Q 24.

Explain Darwin's theory of evolution.

Q 25.

What evidence do we have for the origin of life from inanimate matter? [All India]

Q 26.

A blue colour flower plant denoted by BB is cross bred with that of white colour flower plant denoted by bb.
(a) State the colour of flower you would expect in their F1   generation plants.
(b) What must be the percentage of white flower plants in F2   generation if flowers of  F1  plants are self-pollinated?
(c) State the expected ratio of the genotypes BB and Bb in the F2  progeny. [Delhi]

Q 27.

Name one variation in humans connected with ears.

Q 28.

What constitutes the link between one generation and the next ?

Q 29.

What are the chromosomes XY and XX known as ?

Q 30.

Name one reptile in each case where higher incubation temperature leads to the development of : (a) male progeny, (b) female progeny.

Q 31.

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.

Q 32.

(a)What is meant by ‘heredity’ ? What are the units of heredity.
(b) State Mendel’s first law of inheritance.

Q 33.

(a) What do you understand by the term ‘variation’ ?
(b) Name two human traits which show variation.

Q 34.

What are fossils ? Giving one example, explain how fossils provide evidence for evolution.

Q 35.

Name the various tools of tracing evolutionary relationships which have been used for studying human evolution.

Q 36.

With the help of an example, explain how variation leads to evolution.

Q 37.

(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.

Q 38.

(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.

Q 39.

Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually ? Why or why not ?

Q 40.

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 ?

Q 41.

Explain how sexual reproduction gives rise to more viable variations that asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually ?

Q 42.

Define variation.

Q 43.

Where are the genes located? What is the chemical nature of genes?

Q 44.

How do embryological studies provide evidence for evolution?

Q 45.

Define evolution. Describe the contribution of Lamarck.

Q 46.

Define variation in relation to a species. Why is variation beneficial to the species? [Delhi]

Q 47.

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]

Q 48.

Which of the two, sperm or ovum, decides the sex of the child ?

Q 49.

A new born child has an XY pair of chromosmes. Will it be a baby boy or a baby girl ?

Q 50.

(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 ?