Heredity and Evolution


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


Stanley L. Miller and Harold C. Urey provided evidence regarding origin of life from inanimate matter. They assembled an atmosphere similar to that existed on early earth. The atmosphere had molecules like ammonia, methane and hydrogen sulphide, but no oxygen and kept over water at temperature just below 100 °C. Sparks were passed through the mixture of gases. At the end of a week, 15% carbon from methane had been converted to simple compounds of carbon like amino acids which make-up protein molecules. So, life arose afresh on earth.


Heredity and Evolution

Q 1.

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

Q 2.

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

Q 3.

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 4.

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

Q 5.

Define variation.

Q 6.

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 7.

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

Q 8.

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

Q 9.

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

Q 10.

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 11.

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

Q 12.

Name the scientist who gave the theory of evolution.

Q 13.

Explain Darwin's theory of evolution.

Q 14.

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 15.

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

Q 16.

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 17.

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 18.

(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 19.

What name is given to the sequence of gradual changes over millions of years in which new species are produced ?

Q 20.

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

Q 21.

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

Q 22.

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

Q 23.

(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 24.

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 25.

What is a retrovirus?

Q 26.

Name one variation in humans connected with ears.

Q 27.

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 ?

Q 28.

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

Q 29.

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 30.

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

Q 31.

State whether the following statement is true or false :
Human beings have evolved from chimpanzees.

Q 32.

The forelimbs of a frog, a bird and a man show the same basic design (or basic structure) of bones. What name is given to such organs ?

Q 33.

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

Q 34.

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

Q 35.

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.

Q 36.

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

Q 37.

What are the chromosomes XY and XX known as ?

Q 38.

(a) State one advantage of variation to a species.
(b) What are sex chromosomes ? How many sex chromosomes are there ? Name them.

Q 39.

What do the following symbols used in the topic on heredity represent ?
(a) TT
(b) tt
(c) XX
(d) XY

Q 40.

Name an animal having rudimentary eyes.

Q 41.

What is meant by acquired and inherited traits ? Explain with one example each.

Q 42.

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

Q 43.

Do genetic combination of mothers play a significant role in determining the sex of new born?

Q 44.

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

Q 45.

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

Q 46.

In evolutionary terms, can we say which among bacteria, spiders, fish and chimpanzees have a ‘better body design’ why or why not ?

Q 47.

What is heredity?

Q 48.

Define a gene.

Q 49.

What are the components of the chromosome?

Q 50.

What is a sex chromosome?