Biology

Heredity and Evolution

Question:

(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.

Answer:

(a) Natural selection is the process of evolution of a species whereby characteristics which help individual organisms to survive and reproduce are passed on to their offspring, and those characteristics which do not help are not passed on.
(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.

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Heredity and Evolution

Q 1.

What constitutes the link between one generation and the next ?

Q 2.

Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?

Q 3.

Define evolution. Describe the contribution of Lamarck.

Q 4.

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

Q 5.

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

Q 6.

Who provided the evidence of DNA as the genetic material? Write the names of the components of the DNA molecule.

Q 7.

How do embryological studies provide evidence for evolution?

Q 8.

What type of plants were used by Mendel for conducting his experiments on inheritance ?

Q 9.

Where did life originate on the earth ?

Q 10.

Name the famous book written by Charles Robert Darwin.

Q 11.

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 ?

Q 12.

Give an example of characteristics being used to determine how close two species am in evolutionary terms ?

Q 13.

Can the wing of butterfly and the wing of a bat be considered homologous organs ? Why or why not ?

Q 14.

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

Q 15.

Outline a project which alms to find the dominant coat colour in dogs.

Q 16.

Explain the importance of fossils in deciding evolutionary relationships.

Q 17.

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

Q 18.

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

Q 19.

What is a gene?

Q 20.

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

Q 21.

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 22.

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 23.

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 24.

Name one variation in humans connected with ears.

Q 25.

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

Q 26.

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 27.

(a) Why did Mendel choose pea plants for conducting his experiments on inheritance ?
(b) State Mendel’s second law of inheritance.

Q 28.

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

Q 29.

Name the scientist who gave the theory of evolution.

Q 30.

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 31.

Choose the one term from the following which includes the other three :
broccoli, wild cabbage, cauliflower, cabbage

Q 32.

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

Q 33.

Name two animals having homologous organs and two having analogous organs. Name these organs.

Q 34.

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

Q 35.

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

Q 36.

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

Q 37.

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.

Q 38.

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

Q 39.

Why are the small numbers of surviving tigers a cause of worry from the point of view of genetics ?

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.

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

Q 42.

Define variation.

Q 43.

Define homologous organs.

Q 44.

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

Q 45.

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)]

Q 46.

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

Q 47.

How are fossils formed? Describe, in brief, two methods of determining the age of fossils. [All India]

Q 48.

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 49.

Explain with an example, how genes control the characteristics (or traits).

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 ?